Classical Galactosaemia in Ireland: incidence, complications and outcomes of treatment

Rare liver diseases in Egypt: Clinical and epidemiological characterization

Illnesses that afflict a tiny number of individuals are referred to as rare diseases (RDs), sometimes called orphan diseases. The local healthcare systems are constantly under financial, psychological, and medical strain due to low incidence rates, unusual presentations, flawed diagnostic standards, and a lack of treatment alternatives for these RDs. The effective management of the once widely spread viral hepatitis B and C has altered the spectrum of liver diseases in Egypt during the last several years. The detection of uncommon disorders such as autoimmune, cholestatic, and hereditary liver diseases has also been made easier by the increasing knowledge and greater accessibility of specific laboratory testing. Finally, despite Egypt's large population, there are more uncommon liver disorders than previously thought. This review article discusses the clinical and epidemiological characteristics of a few uncommon liver disorders and the information currently accessible concerning these illnesses in Egypt.

Brain function in classic galactosemia, a galactosemia network (GalNet) members review

Classic galactosemia (CG, OMIM #230400, ORPHA: 79,239) is a hereditary disorder of galactose metabolism that, despite treatment with galactose restriction, affects brain function in 85% of the patients. Problems with cognitive function, neuropsychological/social emotional difficulties, neurological symptoms, and abnormalities in neuroimaging and electrophysiological assessments are frequently reported in this group of patients, with an enormous individual variability. In this review, we describe the role of impaired galactose metabolism on brain dysfunction based on state of the art knowledge. Several proposed disease mechanisms are discussed, as well as the time of damage and potential treatment options. Furthermore, we combine data from longitudinal, cross-sectional and retrospective studies with the observations of specialist teams treating this disease to depict the brain disease course over time. Based on current data and insights, the majority of patients do not exhibit cognitive decline. A subset of patients, often with early onset cerebral and cerebellar volume loss, can nevertheless experience neurological worsening. While a large number of patients with CG suffer from anxiety and depression, the increased complaints about memory loss, anxiety and depression at an older age are likely multifactorial in origin.

Classical Hereditary galactosemia: findings in patients and animal models

Classic galactosemia is a rare inborn error of metabolism that affects the metabolism of galactose, a sugar derived from milk and derivates. Classic galactosemia is caused by variants of the GALT gene, which lead to absent or misfolded forms of the ubiquitously present galactose-1-phosphate uridylyltransferase enzyme (GALT) driving galactose metabolites to accumulate, damaging cells from neurons to hepatocytes. The disease has different prevalence around the world due to different allele frequencies among populations and its symptoms range from cognitive and psychomotor impairment to hepatic, ophthalmological, and bone structural damage. The practice of newborn screening still varies among countries, dairy restriction treatment is a consensus despite advances in preclinical treatment strategies. Recent clinical studies in Duarte variant suggest dairy restriction could be reconsidered in these cases. Despite noteworthy advances in the classic galactosemia understanding, preclinical trials are still crucial to fully understand the pathophysiology of the disease and help propose new treatments. This review aims to report a comprehensive analysis of past studies and state of art research on galactosemia screening, its clinical and preclinical trials, and treatments with the goal of shedding light on this complex and multisystemic innate error of the metabolism.

Incidental Detection of Classical Galactosemia through Newborn Screening for Phenylketonuria: A 10-Year Retrospective Audit to Determine the Efficacy of This Approach

In the UK, Classical Galactosaemia (CG) is identified incidentally from the Newborn Screening (NBS) for phenylketonuria (PKU) using an "Other disorder suspected" (ODS) pathway when phenylalanine (Phe) and tyrosine (Tyr) concentrations are increased. We aimed to determine the efficacy of CG detection via NBS and estimate the incidence of CG in live births in the UK. A survey was sent to all UK NBS laboratories to collate CG cases diagnosed in the UK from 2010 to 2020. Cases of CG diagnosed were determined if detected clinically, NBS, or by family screening, as well as age at diagnosis. Cases referred via the ODS pathway were also collated, including the final diagnosis made. Responses were obtained from 13/16 laboratories. Between 2010 and 2020, a total of 6,642,787 babies were screened, and 172 cases of CG were identified. It should be noted that 85/172 presented clinically, 52/172 were identified by NBS, and 17/172 came from family screening. A total of 117 referrals were made via the ODS pathway, and 45/117 were subsequently diagnosed with CG. Median (interquartile range) age at diagnosis by NBS and clinically was 8 days (7-11) and 10 days (7-16), respectively (Mann-Whitney U test, U = 836.5, p-value = 0.082). The incidence of CG is 1:38,621 live births. The incidence of CG in the UK is comparable with that of other European/western countries. No statistical difference was seen in the timing of diagnosis between NBS and clinical presentation based on the current practice of sampling on day 5. Bringing forward the day of NBS sampling to day 3 would increase the proportion diagnosed with CG by NBS from 52/172 (30.2%) to 66/172 (38.4%).

Racial and ethnic diversity of classic and clinical variant galactosemia in the United States

Classic and clinical variant galactosemia (CG/CVG) are allelic, autosomal recessive disorders that result from deficiency of galactose-1-P uridylyltransferase (GALT). CG/CVG has been reported globally among patients of diverse ancestries, but most large studies of outcomes have included, almost exclusively, patients categorized as White or Caucasian. As a first step to explore whether the cohorts studied are representative of the CG/CVG population at large, we sought to define the racial and ethnic makeup of CG/CVG newborns in a diverse population with essentially universal newborn screening (NBS) for galactosemia: the United States (US). First, we estimated the predicted racial and ethnic distribution of CG/CVG by combining the reported demographics of US newborns from 2016 to 2018 with predicted homozygosity or compound heterozygosity of pathogenic, or likely pathogenic, GALT alleles from the relevant ancestral groups. Incorporating some simplifying assumptions, we predicted that of US newborns diagnosed with CG/CVG, 65% should be White (non-Hispanic), 23% should be Black (non-Hispanic), 10% should be Hispanic, and 2% should be Asian (non-Hispanic). Next, we calculated the observed racial and ethnic distribution of US newborns diagnosed with CG/CVG using available de-identified data from state NBS programs from 2016 to 2018. Of the 235 newborns in this cohort, 41 were categorized as other or unknown. Of the remaining 194, 66% were White (non-Hispanic or ethnicity unknown), 16% were Black (non-Hispanic or ethnicity unknown),15% were Hispanic, and 2% were Asian (non-Hispanic or ethnicity unknown). This observed distribution was statistically indistinguishable from the predicted distribution. To the limits of our study, these data confirm the racial and ethnic diversity of newborns with CG/CVG in the US, demonstrate an approach for estimating CG/CVG racial and ethnic diversity in other populations, and raise the troubling possibility that current understanding of long-term outcomes in CG/CVG may be skewed by ascertainment bias of the cohorts studied.

Lactose and Galactose Content in Spanish Cheeses: Usefulness in the Dietary Treatment of Patients with Galactosaemia

In galactosaemia, a strict galactose-free diet is necessary to prevent or resolve acute symptoms in infants. However, because the body produces up to 10 times more galactose than is found in a galactose-restricted diet, excessively restrictive diets should be avoided in children and adults to prevent nutritional deficiencies. Since cheese is a nutritional source of the calcium necessary for bone health, the latest international guidelines on the management of classical galactosaemia (2017) allow the consumption of cured cheeses with less than 25 mg of galactose/100 g and recommend that each country verifies the adequacy of the cheeses, since most mature cheeses do not always have a lower galactose content. In total, 32 cheese samples were purchased (19 Spanish and 13 international cheeses), and their lactose and galactose contents were analysed using ion chromatography with pulsed amperometric detection (IC-PAD). Five Spanish cheeses contained less than 25 mg of galactose/100 g: García Baquero semi-cured cheese; Hacendado, Gran Reserva and Mahón cured cheeses; and García Baquero Reserva 12-month cured cheese. In addition, eight international cheeses were confirmed as suitable: Comté, Gouda, Gruyere, Maasdam, Parmigiano, Edam, Emmental, and some samples of Cheddar. In addition to the well-known low-galactose Swiss and Dutch cheeses, according to the current results, five Spanish cheeses can be safely consumed. The greater availability of types of cheese favours better bone health in patients with galactosaemia.

Assessment of Dietary Intake of Iodine and Risk of Iodine Deficiency in Children with Classical Galactosaemia on Dietary Treatment

Iodine is an essential mineral required for the synthesis of thyroid hormones. Iodine plays a critical role in growth and neurocognitive development. Classical galactosaemia is a disorder resulting from an inborn error in galactose metabolism. Its current management consists of life-long lactose and galactose dietary restriction. This study estimated dietary intakes of iodine in infants and children with classical galactosaemia in the Republic of Ireland. The diets of 43 participants (aged 7 months-18 years) with classical galactosaemia were assessed for iodine intake using an iodine-specific food frequency questionnaire. Intakes were compared to the European Food Safety Authority (EFSA) dietary recommendations for iodine intake. The potential role of iodine fortification of dairy alternative products was also examined. There were no significant differences observed between sex, ethnicity and parental education and meeting dietary iodine recommendations. Differences, however, were seen between age groups, causing the p value to approach statistical significance (p = 0.06). Infants consuming infant formula were likely to meet iodine recommendations. However, over half (53%) of children aged 1-18 years had average intakes below the recommendations for age. For these children, consumption of iodine-fortified dairy alternative milk was the leading source of iodine in the diets, followed by fish/shellfish and eggs. An assessment of iodine intake should be undertaken during dietetic reviews for those with classical galactosaemia. Mandatory iodine fortification of all dairy alternative products would result in 92% of the total population cohort meeting iodine recommendations based on their current consumption.

The Importance of Neonatal Screening for Galactosemia

Galactosemia is an inborn metabolic disorder caused by a deficient activity in one of the enzymes involved in the metabolism of galactose. The first description of galactosemia in newborns dates from 1908, ever since complex research has been performed on cell and animal models to gain more insights into the molecular and clinical bases of this challenging disease. In galactosemia, the newborn appears to be born in proper health, having a window of opportunity before developing major morbidities that may even be fatal following ingestion of milk that contains galactose. Galactosemia cannot be cured, but its negative consequences on health can be avoided by establishing precocious diagnosis and treatment. All the foods that contain galactose should be eliminated from the diet when there is a suspicion of galactosemia. The neonatal screening for galactosemia can urge early diagnosis and intervention, preventing complications. All galactosemia types may be detected during the screening of newborns for this disorder. The major target is, however, galactose-1-phosphate uridyltransferase (GALT) deficiency galactosemia, which is diagnosed by applying a combination of total galactose and GALT enzyme analysis as well as, in certain programs, mutation screening. Most critically, infants who exhibit symptoms suggestive of galactosemia should undergo in-depth testing for this condition even when the newborn screening shows normal results. The decision to enroll global screening for galactosemia among the specific population still faces many challenges. In this context, the present narrative review provides an updated overview of the incidence, clinical manifestations, diagnosis, therapy, and prognosis of galactosemia, questioning under the dome of these aspects related to the disease the value of its neonatal monitoring.

Feasibility of a Proactive Parent-Implemented Communication Intervention Delivered via Telepractice for Children With Classic Galactosemia

PURPOSE

This study evaluated the feasibility of Babble Boot Camp (BBC) for use with infants with classic galactosemia (CG) starting at less than 6 months of age. BBC is a parent-implemented intervention delivered by speech-language pathologists (SLPs) entirely via telepractice with the potential to increase access to early preventative interventions. We evaluated BBC feasibility based on acceptability, implementation, and practicality.

METHOD

We obtained data from 16 parents of infants with CG (mean age at enrollment = 3.38 months) involved in a large randomized clinical trial of BBC. BBC uses a teach-model-coach-review approach to provide parents with strategies to support their child's communication development. Families completed, on average, eighty-one 15-min sessions over a 20-month intervention period. We drew data from surveys completed by parents at the end of the intervention period, intervention logs maintained by the SLPs, and intervention fidelity checks completed by research assistants.

RESULTS

Data drawn from parent surveys, intervention logs, and intervention fidelity checks revealed high parent acceptability, high rates of completion and compliance, and low costs in terms of parent and clinician time.

CONCLUSION

Results suggest that BBC is feasible for families of infants with CG, warranting further examination of BBC across a broader range of children with CG as well as other infants who are at predictable risk for speech and language impairment.

Determination of the lactose and galactose content of common foods: Relevance to galactosemia

Classical galactosemia (CG) is a disorder of galactose metabolism which results from deficiency of the enzyme galactose‐1‐phosphate uridylyl transferase (GALT). Treatment consists of immediately eliminating galactose from the diet in the new‐born and lifelong restriction of dietary galactose. The inclusion of a wider variety of foods for people with CG may provide many benefits, including improved nutritional adequacy and quality of life. Galactose plays an important role in glycosylation of glycoproteins and glycolipids. Moderate liberalization of galactose restriction has been shown to improve immunoglobulin G (IgG) glycosylation for some individuals with CG. Moreover, recent outcome research suggests that strict restriction of nondairy galactose may have more unfavorable outcomes than moderate liberalization in CG patients. In the current work, based on patient feedback, we have analyzed the lactose and galactose content of different foods available in Ireland. These include a range of cheeses, yogurts, pizzas, soups, biscuits, cakes, pastries, crackers, mayonnaises, salad creams, fat spreads, crisps, corn chips, salamis, and gravies. This work provides information to support the development of a practical food‐based approach to facilitate analysis of dietary galactose intake and to possibly increase overall variety of food choices for people with CG.

Novel mRNA therapy restores GALT protein and enzyme activity in a zebrafish model of classic galactosemia

Messenger RNA (mRNA) has emerged as a novel therapeutic approach for inborn errors of metabolism. Classic galactosemia (CG) is an inborn error of galactose metabolism caused by a severe deficiency of galactose-1-phosphate:uridylyltransferase (GALT) activity leading to neonatal illness and chronic impairments affecting the brain and female gonads. In this proof of concept study, we used our zebrafish model for CG to evaluate the potential of human GALT mRNA (hGALT mRNA) packaged in two different lipid nanoparticles to restore GALT expression and activity at early stages of development. Both one cell-stage and intravenous single-dose injections resulted in hGALT protein expression and enzyme activity in the CG zebrafish (galt knockout) at 5 days post fertilization (dpf). Moreover, the levels of galactose-1-phosphate (Gal-1-P) and galactonate, metabolites that accumulate because of the deficiency, showed a decreasing trend. LNP-packaged mRNA was effectively translated and processed in the CG zebrafish without signs of toxicity. This study shows that mRNA therapy restores GALT protein and enzyme activity in the CG zebrafish model, and that the zebrafish is a suitable system to test this approach. Further studies are warranted to assess whether repeated injections safely mitigate the chronic impairments of this disease.

SRT1720 plays a role in oxidative stress and the senescence of human trophoblast HTR8/SVneo cells induced by D-galactose through the SIRT1/FOXO3a/ROS signalling pathway

D-galactose (D-gal) is a reducing sugar widely distributed in food. In a pregnant animal model exposed to D-gal, D-gal was found to have toxic effects on both the mother and foetus through oxidative stress. However, little is known about the effect of D-gal exposure on the placenta and its underlying mechanism. In this study, we evaluated the effects of D-gal on HTR8/SVneo cells and the mechanisms in vitro. In the present study, the activity of HTR8/SVneo human trophoblasts decreased in a time- and concentration-dependent manner after exposure to D-gal. D-gal resulted in premature senescence of HTR8/SVneo cells, as confirmed by assessing β-galactosidase (SA-β-gal) activity and the expression of senescence-related factor p21. We also verified the damage of oxidative stress induced by D-gal by measuring the expression of reactive oxygen species (ROS), sirtuin 1 (SIRT1) and forkhead box O (FOXO) 3a. SRT1720, as a SIRT1 activator, mitigated D-gal-induced oxidative stress and senescence by upregulating SIRT1 and FOXO3a expression and reducing ROS production. Our data suggest that D-gal may induce HTR8/SVneo premature ageing through the SIRT1/FOXO3a/ROS signalling pathway mediated by oxidative stress and that SIRT1 protects cells from this damage.

Translating principles of precision medicine into speech-language pathology: Clinical trial of a proactive speech and language intervention for infants with classic galactosemia

Precision medicine is an emerging approach to managing disease by taking into consideration an individual’s genetic and environmental profile toward two avenues to improved outcomes: prevention and personalized treatments. This framework is largely geared to conditions conventionally falling into the field of medical genetics. Here, we show that the same avenues to improving outcomes can be applied to conditions in the field of behavior genomics, specifically disorders of spoken language. Babble Boot Camp (BBC) is the first comprehensive and personalized program designed to proactively mitigate speech and language disorders in infants at predictable risk by fostering precursor and early communication skills via parent training. The intervention begins at child age 2 to 5 months and ends at age 24 months, with follow-up testing at 30, 42, and 54 months. To date, 44 children with a newborn diagnosis of classic galactosemia (CG) have participated in the clinical trial of BBC. CG is an inborn error of metabolism of genetic etiology that predisposes up to 85% of children to severe speech and language disorders. Of 13 children with CG who completed the intervention and all or part of the follow-up testing, only one had disordered speech and none had disordered language skills. For the treated children who completed more than one assessment, typical speech and language skills were maintained over time. This shows that knowledge of genetic risk at birth can be leveraged toward proactive and personalized management of a disorder that manifests behaviorally.

Two consecutive pregnancies in a patient with premature ovarian insufficiency in the course of classic galactosemia and a review of the literature

AIM

To present a case report of a patient with classic galactosemia and the Q188R/K285N GALT mutation, who conceived spontaneously twice despite severe ovarian failure. A review of the literature is included.

MATERIALS AND METHODS

A 20-year-old patient with classic galactosemia and premature ovarian insufficiency (POI) came to our attention. We performed a routine hormonal and ultrasound examination confirming low ovarian reserve. Due to low rates of pregnancies in individuals with POI (5%-10%), we were almost certain of the infeasibility of pregnancy.

RESULTS

Surprisingly, several months after hospitalization, the patient conceived without any medical intervention and less than a year after the first birth she became pregnant again. While reviewing the literature, 90 pregnancies among galactosemic patients were identified.

CONCLUSIONS

Ovarian failure is a long-term diet-independent complication of classic galactosemia, pertaining to about 90% of affected individuals. This case confirms its unpredicted course, as even the presence of unfavorable factors (absence of spontaneous puberty, early diagnosis of POI, undetectable AMH) may not preclude the chance for conception.

Toward Preventing Speech and Language Disorders of Known Genetic Origin: First Post-Intervention Results of Babble Boot Camp in Children With Classic Galactosemia

Purpose Babble Boot Camp (BBC) is a package of proactive activities and routines designed to prevent speech and language disorders in infants at predictable risk. It is implemented via parent training and currently undergoing clinical trial in children with a newborn diagnosis of classic galactosemia (CG), a metabolic disease with high risk of speech and language disorders. The purpose of this study is to provide updates to a previous pilot study and to present the first set of post-intervention results. Method The intervention and data collection occurred during child ages < 6-24 months, with follow-up assessments of speech and language at ages 2.5 and 3.5 years. Treatment targets included earliest vocalization rates, babble complexity, speech production accuracy, and vocabulary and syntactic growth. The oldest 15 children with CG (including three untreated controls) completed the first set of follow-up assessments. Aggregate data up to 10 months were available for 17 treated children with CG, six untreated children with CG, and six typical controls. Results At ages 7-9 months, babbling complexity, as measured with mean babbling level, was higher in the treated children with CG than in the untreated children with CG and the typical controls. Prior to 24 months of age, the treated children with CG had greater expressive but not receptive vocabulary sizes than an untreated control. Follow-up testing showed typical language scores for all 12 treated children with CG and typical articulation scores for 11 of these, whereas one of three untreated children with CG had low articulation and expressive language scores. Conclusions The BBC appears to be a viable intervention to support the speech and expressive language development of children with GC. Future studies will evaluate the relative contributions of the earliest and later BBC components to outcomes.

Abnormal N-glycan fucosylation, galactosylation, and sialylation of IgG in adults with classical galactosemia, influence of dietary galactose intake

BACKGROUND

Classical galactosemia (CG) (OMIM #230400) is a rare disorder of carbohydrate metabolism, due to deficiency of galactose-1-phosphate uridyltransferase (EC 2.7.7.12). The pathophysiology of the long-term complications, mainly cognitive, neurological, and female infertility remains poorly understood.

OBJECTIVES

This study investigated (a) the association between specific IgG N-glycosylation biomarkers (glycan peaks and grouped traits) and CG patients (n = 95) identified from the GalNet Network, using hydrophilic interaction ultraperformance liquid chromatography and (b) a further analysis of a GALT c.563A-G/p.Gln188Arg homozygous cohort (n = 49) with correlation with glycan features with patient Full Scale Intelligence Quotient (FSIQ), and (c) with galactose intake.

RESULTS

A very significant decrease in galactosylation and sialylation and an increase in core fucosylation was noted in CG patients vs controls (P < .005). Bisected glycans were decreased in the severe GALT c.563A-G/p.Gln188Arg homozygous cohort (n = 49) (P < .05). Logistic regression models incorporating IgG glycan traits distinguished CG patients from controls. Incremental dietary galactose intake correlated positively with FSIQ for the p.Gln188Arg homozygous CG cohort (P < .005) for a dietary galactose intake of 500 to 1000 mg/d. Significant improvements in profiles with increased galactose intake were noted for monosialylated, monogalactosylated, and monoantennary glycans.

CONCLUSION

These results suggest that N-glycosylation abnormalities persist in CG patients on dietary galactose restriction which may be modifiable to a degree by dietary galactose intake.

Musculoskeletal Health in Premature Ovarian Insufficiency. Part Two: Bone

Accelerated bone loss and muscle loss coexist in women with premature ovarian insufficiency (POI), but there are significant gaps in our understanding of musculoskeletal health in POI. This review describes estrogen signaling in bone and its role in skeletal health and disease. Possible mechanisms contributing to bone loss in different forms of POI and current evidence regarding the utility of available diagnostic tests and therapeutic options are also discussed. A literature review from January 2000 to March 2020 was conducted to identify relevant studies. Women with POI experience significant deterioration in musculoskeletal health due to the loss of protective effects of estrogen. In bone, loss of bone mineral density (BMD) and compromised bone quality result in increased fracture risk; however, tools to assess bone quality such as trabecular bone score (TBS) need to be validated in this population. Timely initiation of HRT is recommended to minimize the deleterious effects of estrogen deficiency on bone in the absence of contraindications; however, the ideal estrogen replacement regimen remains unknown. POI is associated with compromised bone health, regardless of the etiology. Ongoing research is warranted to refine our management strategies to preserve bone health in women with POI.

Virus-Based Nanoreactors with GALT Activity for Classic Galactosemia Therapy

Enzymatic nanoreactors were obtained by galactose-1-phosphate uridylyl-transferase (GALT) encapsulation into plant virus capsids by a molecular self-assembly strategy. The aim of this work was to produce virus-like nanoparticles containing GALT for an enzyme-replacement therapy for classic galactosemia. The encapsulation efficiency and the catalytic constants of bio-nanoreactors were determined by using different GALT and virus coat protein ratios. The substrate affinity of nanoreactors was slightly lower than that of the free enzyme; the activity rate was 16 % of the GALT free enzyme. The enzymatic nanoreactors without functionalization were internalized into different cell lines including fibroblast and kidney cells, but especially into hepatocytes. The enzymatic nanoreactors are an innovative enzyme preparation with potential use for the treatment of classic galactosemia.

Gray and white matter are both affected in classical galactosemia: An explorative study on the association between neuroimaging and clinical outcome

BACKGROUND

Classical Galactosemia (CG) is an inherited disorder of galactose metabolism caused by a deficiency of the galactose-1-phosphate uridylyltransferase (GALT) enzyme resulting in neurocognitive complications. As in many Inborn Errors of Metabolism, the metabolic pathway of CG is well-defined, but the pathophysiology and high variability in clinical outcome are poorly understood. The aim of this study was to investigate structural changes of the brain of CG patients on MRI and their association with clinical outcome.

METHODS

In this prospective cohort study an MRI protocol was developed to evaluate gray matter (GM) and white matter (WM) volume of the cerebrum and cerebellum, WM hyperintensity volume, WM microstructure and myelin content with the use of conventional MRI techniques, diffusion tensor imaging (DTI) and quantitative T1 mapping. The association between several neuroimaging parameters and both neurological and intellectual outcome was investigated.

RESULTS

Twenty-one patients with CG (median age 22 years, range 8-47) and 24 controls (median age 30, range 16-52) were included. Compared to controls, the WM of CG patients was lower in volume and the microstructure of WM was impaired both in the whole brain and corticospinal tract (CST) and the lower R1 values of WM, GM and the CST were indicative of less myelin. The volume of WM lesions were comparable between patients and controls. The 9/16 patients with a poor neurological outcome (defined as the presence of a tremor and/or dystonia), demonstrated a lower WM volume, an impaired WM microstructure and lower R1 values of the WM indicative of less myelin content compared to 7/16 patients without movement disorders. In 15/21 patients with a poor intellectual outcome (defined as an IQ < 85) both GM and WM were affected with a lower cerebral and cerebellar WM and GM volume compared to 6/21 patients with an IQ ≥ 85. Both the severity of the tremor (as indicated by the Tremor Rating Scale) and IQ (as continuous measure) were associated with several neuroimaging parameters such as GM volume, WM volume, CSF volume, WM microstructure parameters and R1 values of GM and WM.

CONCLUSION

In this explorative study performed in patients with Classical Galactosemia, not only WM but also GM pathology was found, with more severe brain abnormalities on MRI in patients with a poor neurological and intellectual outcome. The finding that structural changes of the brain were associated with the severity of long-term complications indicates that quantitative MRI techniques could be of use to explain neurological and cognitive dysfunction as part of the disease spectrum. Based on the clinical outcome of patients, the absence of widespread WM lesions and the finding that both GM and WM are affected, CG could be primarily a GM disease with secondary damage to the WM as a result of neuronal degeneration. To investigate this further the course of GM and WM should be evaluated in longitudinal research, which could also clarify if CG is a neurodegenerative disease.

Deep phenotyping classical galactosemia: clinical outcomes and biochemical markers

Early diagnosis and dietary treatment do not prevent long-term complications, which mostly affect the central nervous system in classical galactosemia patients. The clinical outcome of patients is highly variable, and there is an urgent need for prognostic biomarkers. The aim of this study was first to increase knowledge on the natural history of classical galactosemia by studying a cohort of patients with varying geno- and phenotypes and second to study the association between clinical outcomes and two possible prognostic biomarkers. In addition, the association between abnormalities on brain MRI and clinical outcomes was investigated. Classical galactosemia patients visiting the galactosemia expertise outpatient clinic of the Amsterdam University Medical Centre were evaluated according to the International Classical Galactosemia guideline with the addition of an examination by a neurologist, serum immunoglobulin G N-glycan profiling and a brain MRI. The biomarkers of interest were galactose-1-phosphate levels and N-glycan profiles, and the clinical outcomes studied were intellectual outcome and the presence or absence of movement disorders and/or primary ovarian insufficiency. Data of 56 classical galactosemia patients are reported. The intellectual outcome ranged from 45 to 103 (mean 77 ± 14) and was <85 in 62%. Movement disorders were found in 17 (47%) of the 36 tested patients. In females aged 12 years and older, primary ovarian insufficiency was diagnosed in 12 (71%) of the 17 patients. Significant differences in N-glycan peaks were found between controls and patients. However, no significant differences in either N-glycans or galactose-1-phosphate levels were found between patients with a poor (intellectual outcome < 85) and normal intellectual outcome (intellectual outcome ≥ 85), and with or without movement disorders or primary ovarian insufficiency. The variant patients detected by newborn screening, with previously unknown geno- and phenotypes and currently no long-term complications, demonstrated significantly lower galactose-1-phospate levels than classical patients (P < 0.0005). Qualitative analysis of the MRI's demonstrated brain abnormalities in 18 of the 21 patients, more severely in patients with a lower intellectual outcome and/or with movement disorders. This study demonstrates a large variability in clinical outcome, which varies from a below average intelligence, movement disorders and in females primary ovarian insufficiency to a normal clinical outcome. In our cohort of classical galactosemia patients, galactose-1-phosphate levels and N-glycan variations were not associated with clinical outcomes, but galactose-1-phosphate levels did differentiate between classical and variant patients detected by newborn screening. The correlation between brain abnormalities and clinical outcome should be further investigated by quantitative analysis of the MR images. The variability in clinical outcome necessitates individual and standardized evaluation of all classical galactosemia patients.

Classical galactosemia: neuropsychological and psychosocial functioning beyond intellectual abilities

Background

Despite early diagnosis and treatment, Classical Galactosemia (CG) patients frequently develop long-term complications, such as cognitive impairment. Available literature primarily reports on general intellectual abilities and shows a substantially lower Full Scale Intelligence Quotient (FSIQ) in CG patients than in the general population. Both problems in social functioning as well as internalizing problems are often reported in CG patients. The combination of intelligence, cognitive functioning, behavior and social functioning has not been studied systematically in CG patients.

Methods

To determine if CG patients demonstrate a specific neuropsychological and psychosocial profile, we investigated intelligence, functioning on multiple cognitive domains, behavior and social functioning with a comprehensive neuropsychological test battery and questionnaires (self- and proxy-reported).

Results

The data of 48 patients, aged 4–47 years are reported. FSIQ ranged from 45 to 103 (mean 77 ± 14). A negative correlation between age and FSIQ was demonstrated (p = 0.037) which resulted directly from the inclusion of four young ‘milder’ patients detected by newborn screening (NBS) with an expected better clinical outcome. Compared to normative data, patients had significantly lower but highly variable scores on all cognitive domains, especially on tests requiring mental speed. In the context of the FSIQ, 43% of the cognitive test results exceeded IQ based expectations. Overall, the patients’ scores on social functioning were in the normal range but internalizing problems were frequently reported. In our cohort, an early initiation of dietary treatment due to NBS or family screening did not result in a more favorable neuropsychological outcome.

Conclusions

In this study, we demonstrated that as a cohort, CG patients have a below average intelligence and impaired cognitive functioning without a distinctive neuropsychological profile. The effect of age on neurocognitive functioning should be assessed in longitudinal studies. Social functioning was not impaired, but patients may be at risk for internalizing problems. Considering the large variability in cognitive, behavioral and social functioning and the finding that cognitive outcomes may exceed IQ based expectations, an individual evaluation and follow-up is warranted in all CG patients to ensure timely support if needed.

An extensive computational approach to analyze and characterize the functional mutations in the galactose-1-phosphate uridyl transferase (GALT) protein responsible for classical galactosemia

Type I galactosemia is a very rare autosomal recessive genetic metabolic disorder that occurs because of the mutations present in the galactose-1-phosphate uridyl transferase (GALT) gene, resulting in a deficiency of the GALT enzyme. The action of the GALT enzyme is to convert galactose-1-phosphate and uridine diphosphate glucose into glucose-1-phosphate (G1P) and uridine diphosphate-galactose, a crucial second step of the Leloir pathway. A missense mutation in the GALT enzyme leads to variable galactosemia's clinical presentations, ranging from mild to severe. Our study aimed to employ a comprehensive computational pipeline to analyze the most prevalent missense mutations (p.S135L, p.K285 N, p.Q188R, and p.N314D) responsible for galactosemia; these genes could serve as potential targets for chaperone therapy. We analyzed the four mutations through different computational analyses, including amino acid conservation, in silico pathogenicity and stability predictions, and macromolecular simulations (MMS) at 50 ns The stability and pathogenicity predictors showed that the p.Q188R and p.S135L mutants are the most pathogenic and destabilizing. In agreement with these results, MMS analysis demonstrated that the p.Q188R and p.S135L mutants possess higher deviation patterns, reduced compactness, and intramolecular H-bonds of the protein. This could be due to the physicochemical modifications that occurred in the mutants p.S135L and p.Q188R compared to the native. Evolutionary conservation analysis revealed that the most prevalent mutations positions were conserved among different species except N314. The proposed research study is intended to provide a basis for the therapeutic development of drugs and future treatment of classical galactosemia and possibly other genetic diseases using chaperone therapy.

Clinical and whole-exome sequencing findings in two siblings from Hani ethnic minority with congenital glycosylation disorders

BACKGROUND

PMM2-CDG, is the most common N-linked glycosylation disorder and subtype among all CDG syndromes, which are a series of genetic disorders involving the synthesis and attachment of glycoproteins and glycolipid glycans. The mutations of PMM2-CDG might lead to the loss of PMM2, which is responsible for the conversion of mannose 6- phosphate into mannose 1-phosphate. Most patients with PMM2-CDG have central nervous system involvement, abnormal coagulation, and hepatopathy. The neurological symptoms of PMM2-CDG are intellectual disability (ID), cerebellar ataxia, and peripheral neuropathy. Now, over 100 new CDG cases have been reported. However, each type of CDG is very rare, and CDGs are problematic to diagnose. In addition, few CDGs have been reported in the Chinese population.

CASE PRESENTATION

Here we present a Hani ethnic minority family including two siblings with congenital glycosylation disorders. Whole-exome sequencing revealed compound heterozygous for one novel mutation (c.241-242 del variant) and previously reported mutation (c.395 T > C) in gene of PMM2. Two mutations were found in proband and her sibling by whole-exome sequencing. The mutations were identified in this family by Sanger sequencing and no mutations were detected in the normal control.

CONCLUSIONS

This is the first report to describe mutations in two siblings of Hani ethnic minority which is one of five ethnic groups found only in Yunnan with a population of more than 1 million.

Insights into the Pathophysiology of Infertility in Females with Classical Galactosaemia

Classical galactosaemia (CG) (OMIM 230400) is a rare inborn error of galactose metabolism caused by the deficiency of the enzyme galactose-1-phosphate uridylyltransferase (GALT, EC 2.7.7.12). Primary ovarian insufficiency (POI) is the most common long-term complication experienced by females with CG, presenting with hypergonadotrophic hypoestrogenic infertility affecting at least 80% of females despite new-born screening and lifelong galactose dietary restriction. In this review, we describe the hypothesized pathophysiology of POI from CG, implications of timing of the ovarian dysfunction, and the new horizons and future prospects for treatments and fertility preservation.

Clinical and molecular characteristics and time of diagnosis of patients with classical galactosemia in an unscreened population in Turkey

Classical galactosemia is an autosomal recessive inborn error of metabolism caused by biallelic pathogenic variants in the GALT gene. With the benefit of early diagnosis by newborn screening, the acute presentation of galactosemia can be prevented. In this study, we describe the clinical phenotypes, time of diagnosis and GALT genotypes of 76 galactosemia patients from Turkey, where the disease is not yet included in the newborn screening program. The median age at first symptom was 10 days (range 5-20), while the median age at diagnosis was 30 days (range 17-53). Nearly half of the patients (36 patients, 47.4%) were diagnosed later than age 1 month. Fifty-eight individuals were found to have 18 different pathogenic variants in their 116 mutant alleles. In our sample, Q188R variant has the highest frequency with 53%, the other half of the allele frequency of the patients showed 17 different genotypes. Despite presenting with typical clinical manifestations, classical galactosemia patients are diagnosed late in Turkey. Due to the geographical location of our country, different pathogenic GALT variants may be seen in Turkish patients. In the present study, a clear genotype-phenotype correlation could not be established in patients.

Including Classical Galactosaemia in the Expanded Newborn Screening Panel Using Tandem Mass Spectrometry for Galactose-1-Phosphate

Galactosaemia has been included in various newborn screening programs since 1963. Several methods are used for screening; however, the predominant methods used today are based on the determination of either galactose-1-phosphate uridyltransferase (GALT) activity or the concentration of total galactose. These methods cannot be multiplexed and therefore require one full punch per sample. Since the introduction of mass spectrometry in newborn screening, many diseases have been included in newborn screening programs. Here, we present a method for including classical galactosaemia in an expanded newborn screening panel based on the specific determination of galactose-1-phosphate by tandem mass spectrometry. The existing workflow only needs minor adjustments, and it can be run on the tandem mass spectrometers in routine use. Furthermore, compared to the currently used methods, this novel method has a superior screening performance, producing significantly fewer false positive results. We present data from 5500 routine newborn screening samples from the Danish Neonatal Screening Biobank. The cohort was enriched by including 14 confirmed galactosaemia positive samples and 10 samples positive for other metabolic disorders diagnosed through the Danish newborn screening program. All galactosaemia positive samples were identified by the method with no false positives. Furthermore, the screening performance for other metabolic disorders was unaffected.

Screening for galactosemia: is there a place for it?

Galactose is a hexose essential for production of energy, which has a prebiotic role and is essential for galactosylation of endogenous and exogenous proteins, ceramides, myelin sheath metabolism and others. The inability to metabolize galactose results in galactosemia. Galactosemia is an autosomal recessive disorder that affects newborns who are born asymptomatic, apparently well and healthy, then develop serious morbidity and mortality upon consuming milk that contains galactose. Those with galactosemia have a deficiency of an enzyme: classic galactosemia (type 1) results from severe deficiency of galactose-1-uridylyltransferase, while galactosemia type II results from galactokinase deficiency and type III results from galactose epimerase deficiency. Many countries include neonatal screening for galactosemia in their national newborn screening program; however, others do not, as the condition is rather rare, with an incidence of 1:30,000-1:100,000, and screening may be seen as not cost-effective and logistically demanding. Early detection and intervention by restricting galactose is not curative but is very rewarding, as it prevents deaths, mental retardation, liver cell failure, renal tubular acidosis and neurological sequelae, and may lead to resolution of cataract formation. Hence, national newborn screening for galactosemia prevents serious potential life-long suffering, morbidity and mortality. Recent advances in communication and biotechnology promise facilitation of logistics of neonatal screening, including improved cost-effectiveness.

Movement disorders and nonmotor neuropsychological symptoms in children and adults with classical galactosemia

Although movement disorders (MDs) are known complications, the exact frequency and severity remains uncertain in patients with classical galactosemia, especially in children. We determined the frequency, classification and severity of MDs in a cohort of pediatric and adult galactosemia patients, and assessed the association with nonmotor neuropsychological symptoms and daily functioning. Patients from seven centers in the United Kingdom and the Netherlands with a confirmed galactosemia diagnosis were invited to participate. A videotaped neurological examination was performed and an expert panel scored the presence, classification and severity of MDs. Disease characteristics, nonmotor neuropsychological symptoms, and daily functioning were evaluated with structured interviews and validated questionnaires (Achenbach, Vineland, Health Assessment Questionnaire, SIP68). We recruited 37 patients; 19 adults (mean age 32.6 years) and 18 children (mean age 10.7 years). Subjective self-reports revealed motor symptoms in 19/37 (51.4%), similar to the objective (video) assessment, with MDs in 18/37 patients (48.6%). The objective severity scores were moderate to severe in one third (6/37). Dystonia was the overall major feature, with additional tremor in adults, and myoclonus in children. Behavioral or psychiatric problems were present in 47.2%, mostly internalizing problems, and associated with MDs. Daily functioning was significantly impaired in the majority of patients. Only one patient received symptomatic treatment for MDs. We show that MDs and nonmotor neuropsychological symptoms are frequent in both children and adults with classical galactosemia.

The natural history of classic galactosemia: lessons from the GalNet registry

BACKGROUND

Classic galactosemia is a rare inborn error of carbohydrate metabolism, caused by a severe deficiency of the enzyme galactose-1-phosphate uridylyltransferase (GALT). A galactose-restricted diet has proven to be very effective to treat the neonatal life-threatening manifestations and has been the cornerstone of treatment for this severe disease. However, burdensome complications occur despite a lifelong diet. For rare diseases, a patient disease specific registry is fundamental to monitor the lifespan pathology and to evaluate the safety and efficacy of potential therapies. In 2014, the international Galactosemias Network (GalNet) developed a web-based patient registry for this disease, the GalNet Registry. The aim was to delineate the natural history of classic galactosemia based on a large dataset of patients.

METHODS

Observational data derived from 15 countries and 32 centers including 509 patients were acquired between December 2014 and July 2018.

RESULTS

Most affected patients experienced neonatal manifestations (79.8%) and despite following a diet developed brain impairments (85.0%), primary ovarian insufficiency (79.7%) and a diminished bone mineral density (26.5%). Newborn screening, age at onset of dietary treatment, strictness of the galactose-restricted diet, p.Gln188Arg mutation and GALT enzyme activity influenced the clinical picture. Detection by newborn screening and commencement of diet in the first week of life were associated with a more favorable outcome. A homozygous p.Gln188Arg mutation, GALT enzyme activity of ≤ 1% and strict galactose restriction were associated with a less favorable outcome.

CONCLUSION

This study describes the natural history of classic galactosemia based on the hitherto largest data set.

Classic galactosaemia in the Greek Cypriot population: An epidemiological and molecular study

Classic galactosaemia is an inherited metabolic disorder of galactose metabolism caused by deficiency of the enzyme galactose-1-phosphate uridyltransferase (GALT) resulting from mutations in the GALT gene. The objectives of the present study were the determination of the carrier frequency of classic galactosaemia in the Greek Cypriot population and the molecular characterization of the disease alleles. We performed an epidemiological study involving 528 Greek Cypriots originating from all parts of Cyprus. Carriers were identified by measuring GALT activity in red blood cells and were subsequently subjected to mutation analysis. A total of five mutations were identified in patients and carriers of classic galactosaemia: a large deletion of 8.5 kb previously reported by us (55% of alleles), the known mutations p.Lys285Asn (30%), p.Pro185Ser (5%), and c.820+13A>G (5%), and a novel mutation c.378-12G>A (5%). Interestingly, the most common mutation in European populations, p.Gln188Arg, was not identified in this Cypriot cohort. The carrier frequency for classic galactosaemia among Greek Cypriots was estimated to be 1:88, predicting a homozygote incidence of 1:31,000 births. The Duarte 1 and Duarte 2 variants were found to be present at a frequency of 5.5% and 2.5%, respectively.

Toward a paradigm shift from deficit-based to proactive speech and language treatment: Randomized pilot trial of the Babble Boot Camp in infants with classic galactosemia

Background: Speech and language therapy is typically initiated reactively after a child shows delays. Infants with classic galactosemia (CG), a metabolic disease with a known high risk for both speech and language disorders, hold the keys towards evaluating whether preventive treatment is effective when the risks are known at birth. We present pilot data from a randomized parallel trial of an innovative proactive speech and language intervention program, the Babble Boot Camp (BBC). 

Method: Five children with CG, otherwise healthy, participated in the study from approximately 2 to 24 months of age. One of these was randomly selected as control receiving conventional management, which typically starts at age 2-3 years. A pediatric speech-language pathologist met weekly via telepractice with the parents in the treatment cohort. Parents implemented the prespeech, speech, and language stimulation and expansion activities according to the intervention protocol. The control child was still too young for conventional treatment. Primary outcome measures were speech sound production complexity in babble and speech and expressive vocabulary size. Secondary outcome measures were vocalization rates and developmental milestones in communication, motor, and cognition. The trial is ongoing.

Results:  All four treated children had higher speech sound skills in babble, three had higher speech sound skills in meaningful speech, two had higher expressive vocabularies, three had higher global developmental scores, and two had higher vocalization rates, compared to the control child with CG.

Discussion: Given the high risk for speech and language delays in children with CG, finding on-schedule abilities in two or more of the treated children but not the untreated child is unexpected under random conditions. The trends toward beneficial effects of the BBC on speech sound production, expressive language, and communication milestones warrant appropriately powered larger clinical trials with full randomization.

Trial registration: ClinicalTrials.gov NCT03838016 (12 ^th February 2019).

Toward a paradigm shift from deficit-based to proactive speech and language treatment: Randomized pilot trial of the Babble Boot Camp in infants with classic galactosemia

Background: Speech and language therapy is typically initiated reactively after a child shows delays. Infants with classic galactosemia (CG), a metabolic disease with a known high risk for both speech and language disorders, hold the keys towards evaluating whether preventive treatment is effective when the risks are known at birth. We present pilot data from a randomized parallel trial of an innovative proactive speech and language intervention program, the Babble Boot Camp (BBC).  Method: Five children with CG, otherwise healthy, participated in the study from approximately 2 to 24 months of age. One of these was randomly selected as control receiving conventional management, which typically starts at age 2-3 years. A pediatric speech-language pathologist met weekly via telepractice with the parents in the treatment cohort. Parents implemented the prespeech, speech, and language stimulation and expansion activities according to the intervention protocol. The control child was still too young for conventional treatment. Primary outcome measures were speech sound production complexity in babble and speech and expressive vocabulary size. Secondary outcome measures were vocalization rates and developmental milestones in communication, motor, and cognition. The trial is ongoing. Results:  All four treated children had higher speech sound skills in babble, three had higher speech sound skills in meaningful speech, two had higher expressive vocabularies, three had higher global developmental scores, and two had higher vocalization rates, compared to the control child with CG. Discussion: Given the high risk for speech and language delays in children with CG, finding on-schedule abilities in two or more of the treated children but not the untreated child is unexpected under random conditions. The trends toward beneficial effects of the BBC on speech sound production, expressive language, and communication milestones warrant appropriately powered larger clinical trials with full randomization. Trial registration: ClinicalTrials.gov NCT03838016 (12 th February 2019).

Arginine does not rescue p.Q188R mutation deleterious effect in classic galactosemia

Background

Classic galactosemia is a rare genetic metabolic disease with an unmet treatment need. Current standard of care fails to prevent chronically-debilitating brain and gonadal complications.

Many mutations in the GALT gene responsible for classic galactosemia have been described to give rise to variants with conformational abnormalities. This pathogenic mechanism is highly amenable to a therapeutic strategy based on chemical/pharmacological chaperones. Arginine, a chemical chaperone, has shown beneficial effect in other inherited metabolic disorders, as well as in a prokaryotic model of classic galactosemia.

The p.Q188R mutation presents a high prevalence in the Caucasian population, making it a very clinically relevant mutation. This mutation gives rise to a protein with lower conformational stability and lower catalytic activity. The aim of this study is to assess the potential therapeutic role of arginine for this mutation.

Methods

Arginine aspartate administration to four patients with the p.Q188R/p.Q188R mutation, in vitro studies with three fibroblast cell lines derived from classic galactosemia patients as well as recombinant protein experiments were used to evaluate the effect of arginine in galactose metabolism. This study has been registered at https://clinicaltrials.gov (NCT03580122) on 09 July 2018. Retrospectively registered.

Results

Following a month of arginine administration, patients did not show a significant improvement of whole-body galactose oxidative capacity (p = 0.22), erythrocyte GALT activity (p = 0.87), urinary galactose (p = 0.52) and urinary galactitol levels (p = 0.41). Patients’ fibroblasts exposed to arginine did not show changes in GALT activity. Thermal shift analysis of recombinant p.Q188R GALT protein in the presence of arginine did not exhibit a positive effect.

Conclusions

This short pilot study in four patients homozygous for the p.Q188R/p.Q188R mutation reveals that arginine has no potential therapeutic role for galactosemia patients homozygous for the p.Q188R mutation.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0954-8) contains supplementary material, which is available to authorized users.

Fertility in classical galactosaemia, a study of N-glycan, hormonal and inflammatory gene interactions

BACKGROUND

Classical Galactosaemia (CG) (OMIM #230400) is a rare inborn error of galactose metabolism caused by deficiency of the enzyme galactose-1-phosphate uridylyltransferase (GALT). Long-term complications persist in treated patients despite dietary galactose restriction with significant variations in outcomes suggesting epigenetic glycosylation influences. Primary Ovarian Insufficiency (POI) is a very significant complication affecting females with follicular depletion noted in early life. We studied specific glycan synthesis, leptin system and inflammatory gene expression in white blood cells as potential biomarkers of infertility in 54 adults with CG adults (27 females and 27 males) (age range 17-51 yr) on a galactose-restricted diet in a multi-site Irish and Dutch study. Gene expression profiles were tested for correlation with a serum Ultra-high Performance Liquid Chromatography (UPLC)-Immunoglobulin (IgG)-N-glycan galactose incorporation assay and endocrine measurements.

RESULTS

Twenty five CG females (93%) had clinical and biochemical evidence of POI. As expected, the CG female patients, influenced by hormone replacement therapy, and the healthy controls of both genders showed a positive correlation between log leptin and BMI but this correlation was not apparent in CG males. The strongest correlations between serum leptin levels, hormones, G-ratio (galactose incorporation assay) and gene expression data were observed between leptin, its gene and G-Ratios data (rs = - 0.68) and (rs = - 0.94) respectively with lower circulating leptin in CG patients with reduced IgG galactosylation. In CG patients (males and females analysed as one group), the key glycan synthesis modifier genes MGAT3 and FUT8, which influence glycan chain bisecting and fucosylation and subsequent cell signalling and adhesion, were found to be significantly upregulated (p < 0.01 and p < 0.05) and also the glycan synthesis gene ALG9 (p < 0.01). Both leptin signalling genes LEP and LEPR were found to be upregulated (p < 0.01) as was the inflammatory genes ANXA1 and ICAM1 and the apoptosis gene SEPT4 (p < 0.01).

CONCLUSIONS

These results validate our previous findings and provide novel experimental evidence for dysregulation of genes LEP, LEPR, ANXA1, ICAM1 and SEPT4 for CG patients and combined with our findings of abnormalities of IgG glycosylation, hormonal and leptin analyses elaborate on the systemic glycosylation and cell signalling abnormalities evident in CG which likely influence the pathophysiology of POI.

Profiling of intracellular metabolites produced from galactose and its potential for galactosemia research

BACKGROUND

Clinical outcome of patients with a classical presentation of galactosemia (classical patients) varies substantially, even between patients with the same genotype. With current biomarkers, it is not possible to predict clinical outcome early in life. The aim of this study was to develop a method to provide more insight into galactose metabolism, which allows quantitative assessment of residual galactose metabolism in galactosemia patients. We therefore developed a method for galactose metabolite profiling (GMP) in fibroblasts using [U-13C]-labeled galactose.

METHODS

GMP analysis was performed in fibroblasts of three classical patients, three variant patients and three healthy controls. The following metabolites were analyzed: [U13C]-galactose, [U13C]-galactose-1-phosphate (Gal-1-P) and [13C6]- uridine diphosphate(UDP)-galactose. The ratio of [U13C]-Gal-1-P/ [13C6]-UDP-galactose was defined as the galactose index (GI).

RESULTS

All patient cell lines could be distinguished from the control cell lines and there was a clear difference between variant and classical patients. Variant patients had lower levels of [U13C]-galactose and [U13C]-Gal-1-P than classical patients (though substantially higher than healthy controls) and higher levels of [13C6]-UDP-galactose than classical patients (though substantially lower than healthy controls) resulting in a different GI in all groups.

CONCLUSIONS

GMP in fibroblasts is a sensitive method to determine residual galactose metabolism capacity, which can discriminate between patients with a classical presentation of galactosemia, patients with a variant presentation and healthy controls. GMP may be a useful method for early prognostication after further validation in a larger cohort of patients representing the full phenotypic spectrum of galactosemia.

Extreme neonatal hyperbilirubinemia, acute bilirubin encephalopathy, and kernicterus spectrum disorder in children with galactosemia

BACKGROUND

Galactosemia has not been recognized as a cause of extreme neonatal hyperbilirubinemia, although growing evidence supports this association.

METHODS

In a retrospective cohort study, we identified children with galactosemia due to GALT deficiency using the Danish Metabolic Laboratory Database. Among these, we identified children with extreme neonatal hyperbilirubinemia or symptoms of ABE. Extreme neonatal hyperbilirubinemia was defined as maximum total serum bilirubin (TSB_max)) level ≥450 µmol/L and a ratio of conjugated serum bilirubin/TSB <0.30.

RESULTS

We identified 21 children with galactosemia (incidence:1:48,000). Seven children developed extreme neonatal hyperbilirubinemia (median [range] TSB_max level: 491 [456-756] µmol/L), accounting for 1.7% of all extreme neonatal hyperbilirubinemia cases. During the first 10 days of life, hyperbilirubinemia was predominantly of unconjugated type. Four children developed symptoms of intermediate/advanced ABE. One additional child had symptoms of intermediate/advanced ABE without having extreme neonatal hyperbilirubinemia. On follow-up, one child had KSD.

CONCLUSIONS

Galactosemia is a potential cause of extreme neonatal hyperbilirubinemia, ABE, and KSD. It is crucial that putative galactosemic children are treated aggressively with phototherapy to prevent ABE and KSD. Thus it is important that galactosemia is part of the work up for unconjugated hyperbilirubinemia.

Hereditary galactosemia

Hereditary galactosemia is an inborn error of carbohydrate metabolism. Galactose is metabolized by Leloir pathway enzymes; galactokinase (GALK), galactose-1-phosphate uridylyltransferase (GALT) and UDP-galactose 4-epimerase (GALE). The defects in these enzymes cause galactosemia in an autosomal recessive manner. The severe GALT deficiency, or classic galactosemia, is life-threatening in the newborn period. The treatment for classic galactosemia is dietary restriction of lactose. Although implementation of lactose restricted diet is efficient in resolving the acute complications, it is not sufficient to prevent long-term complications affecting the brain and female gonads, the two main target organs of damage. Implementation of molecular genetics diagnostic tools and GALT enzyme assays are instrumental in distinguishing classic galactosemia from clinical and biochemical variant forms of GALT deficiency. Better understanding of mechanisms responsible for the phenotypic variation even within the same genotype is essential to provide appropriate counseling for families. Utilization of a lactose restricted diet is also recommended for GALK deficiency and some rare forms of GALE deficiency. Novel modes of therapies are being explored; they may be beneficial if access issues to the affected tissues are circumvented and optimum use of therapeutic window is achieved.

Validation of an automated ultraperformance liquid chromatography IgG N-glycan analytical method applicable to classical galactosaemia

Background

Classical galactosaemia (OMIM #230400) is a rare disorder of carbohydrate metabolism caused by deficiency of the galactose-1-phosphate uridyltransferase enzyme. The pathophysiology of the long-term complications, mainly cognitive, neurological and female fertility problems, remains poorly understood. Current clinical methods of biochemical monitoring lack precision and individualization with an identified need for improved biomarkers for this condition.

Methods

We report the development and detailed validation of an automated ultraperformance liquid chromatography N-glycan analytical method of high peak resolution applied to galactose incorporation into human serum IgG. Samples are prepared on 96-well plates and the workflow features rapid glycoprotein denaturation, enzymatic glycan release, glycan purification on solid-supported hydrazide, fluorescent labelling and post-labelling clean-up with solid-phase extraction.

Results

This method is shown to be accurate and precise with repeatability (cumulative coefficients of variation) of 2.0 and 8.5%, respectively, for G0/G1 and G0/G2 ratios. Both serum and processed N-glycan samples were found to be stable at room temperature and in freeze–thaw experiments.

Conclusions

This high-throughput method of IgG galactose incorporation is robust, affordable and simple. This method is validated with the potential to apply as a biomarker for treatment outcomes for galactosaemia.

Catalogue of inherited disorders found among the Irish Traveller population

Background Irish Travellers are an endogamous, nomadic, ethnic minority population mostly resident on the island of Ireland with smaller populations in Europe and the USA. High levels of consanguinity result in many rare autosomal recessive disorders. Due to founder effects and endogamy, most recessive disorders are caused by specific homozygous mutations unique to this population. Key clinicians and scientists with experience in managing rare disorders seen in this population have developed a de facto advisory service on differential diagnoses to consider when faced with specific clinical scenarios.

Objective(s) To catalogue all known inherited disorders found in the Irish Traveller population.

Methods We performed detailed literature and database searches to identify relevant publications and the disease mutations of known genetic disorders found in Irish Travellers.

Results We identified 104 genetic disorders: 90 inherited in an autosomal recessive manner; 13 autosomal dominant and one a recurring chromosomal duplication.

Conclusion We have collated our experience of inherited disorders found in the Irish Traveller population to make it publically available through this publication to facilitate a targeted genetic approach to diagnostics in this ethnic group.

The Irish DNA Atlas: Revealing Fine-Scale Population Structure and History within Ireland

The extent of population structure within Ireland is largely unknown, as is the impact of historical migrations. Here we illustrate fine-scale genetic structure across Ireland that follows geographic boundaries and present evidence of admixture events into Ireland. Utilising the 'Irish DNA Atlas', a cohort (n = 194) of Irish individuals with four generations of ancestry linked to specific regions in Ireland, in combination with 2,039 individuals from the Peoples of the British Isles dataset, we show that the Irish population can be divided in 10 distinct geographically stratified genetic clusters; seven of 'Gaelic' Irish ancestry, and three of shared Irish-British ancestry. In addition we observe a major genetic barrier to the north of Ireland in Ulster. Using a reference of 6,760 European individuals and two ancient Irish genomes, we demonstrate high levels of North-West French-like and West Norwegian-like ancestry within Ireland. We show that that our 'Gaelic' Irish clusters present homogenous levels of ancient Irish ancestries. We additionally detect admixture events that provide evidence of Norse-Viking gene flow into Ireland, and reflect the Ulster Plantations. Our work informs both on Irish history, as well as the study of Mendelian and complex disease genetics involving populations of Irish ancestry.

Rigor of non-dairy galactose restriction in early childhood, measured by retrospective survey, does not associate with severity of five long-term outcomes quantified in 231 children and adults with classic galactosemia

One of many vexing decisions faced by parents of an infant with classic galactosemia (CG) is how carefully to restrict non-dairy galactose from their growing child's diet. Until recently, many experts recommended vigorous lifelong dietary restriction of milk and all high-galactose dairy products as well as some non-dairy sources of galactose such as legumes and specific fruits and vegetables. Recently, experts have begun to relax their recommendations. The new recommendations, that restrict only high galactose dairy products, were made in the face of uncertainty, however, because no sufficiently powered study had been reported testing for possible association between rigor of non-dairy galactose restriction and severity of long-term outcomes in CG. Here we describe the largest study of diet and outcomes in CG reported to date, conducted using information gathered from 231 patients with CG and 71 unaffected sibling controls. We compared rigor of dietary galactose restriction, measured using a 4-point scale by a retrospective parent-response survey, with outcomes including growth, adaptive behaviors, receipt of speech therapy, receipt of special educational services, and for girls and women, a plasma marker of ovarian function (AMH). Our results confirmed the expected differences between patients and controls, but among patients showed no significant association between rigor of non-dairy galactose restriction in early childhood and any of the outcomes quantified. Indeed, some weak associations were seen suggesting that rigorous restriction of non-dairy galactose may be deleterious rather than beneficial. Despite limitations, these findings support the ongoing trend toward diet liberalization with regard to non-dairy sources of galactose for children and adults with classic galactosemia.

Galactose-1-phosphate uridyltransferase deficiency: A literature review of the putative mechanisms of short and long-term complications and allelic variants

Galactosemia type 1 is an autosomal recessive disorder of galactose metabolism, determined by a deficiency in the enzyme galactose-1-phosphate uridyltransferase (GALT). GALT deficiency is classified as severe or variant depending on biochemical phenotype, genotype and potential to develop acute and long-term complications. Neonatal symptoms usually resolve after galactose-restricted diet; however, some patients, despite the diet, can develop long-term complications, in particular when the GALT enzyme activity results absent or severely decreased. The mechanisms of acute and long-term complications are still discussed and several hypotheses are presented in the literature like enzymatic inhibition, osmotic stress, endoplasmic reticulum stress, oxidative stress, defects of glycosylation or epigenetic modification. This review summarizes the current knowledge of galactosemia, in particular the putative mechanisms of neonatal and long-term complications and the molecular genetics of GALT deficiency.

Fertility in adult women with classic galactosemia and primary ovarian insufficiency

OBJECTIVE

To study pregnancy chance in adult women with classic galactosemia and primary ovarian insufficiency. Despite dietary treatment, >90% of women with classic galactosemia develop primary ovarian insufficiency, resulting in impaired fertility. For many years, chance of spontaneous conception has not been considered, leading to counseling for infertility. But an increasing number of reports on pregnancies in this group questions whether current counseling approaches are correct.

DESIGN

Multicenter retrospective observational study.

SETTING

Metabolic centers.

PATIENT(S)

Adult women (aged >18 y) with confirmed classic galactosemia and primary ovarian insufficiency were included.

INTERVENTION(S)

Participants and medical records were consulted to obtain study data in a standardized manner with the use of a questionnaire.

MAIN OUTCOME MEASURE(S)

Conception opportunities, time to pregnancy, pregnancy outcome, hormone replacement therapy use, fertility counseling, and the participants' vision of fertility were evaluated. Potential predictive factors for increased pregnancy chance were explored.

RESULT(S)

Eighty-five women with classic galactosemia and primary ovarian insufficiency participated. Twenty-one women actively attempted to conceive or did not take adequate contraceptive precautions. Of these 21 women, nine became pregnant spontaneously (42.9%). This was higher than reported in primary ovarian insufficiency due to other causes (5%-10%). After a period of 12 months, a cumulative proportion of 27.8% of couples had conceived, which increased to 48.4% after 24 months and 61.3% after 27 months. Predictive factors could not be identified. A considerable miscarriage rate of 30% was observed (6 of 20 pregnancies). Although a substantial proportion of women expressed a child-wish (n = 28/53; 52.8%), the vast majority of participants (n = 43/57; 75.4%) considered conceiving to be highly unlikely, owing to negative counseling in the past.

CONCLUSION(S)

The pregnancy rate in women with classic galactosemia and primary ovarian insufficiency was higher than for women with primary ovarian insufficiency of any cause. This shifting paradigm carries significant implications for fertility counseling and potential application of fertility preservation techniques.

Sweet and sour: an update on classic galactosemia

Classic galactosemia is a rare inherited disorder of galactose metabolism caused by deficient activity of galactose-1-phosphate uridylyltransferase (GALT), the second enzyme of the Leloir pathway. It presents in the newborn period as a life-threatening disease, whose clinical picture can be resolved by a galactose-restricted diet. The dietary treatment proves, however, insufficient in preventing severe long-term complications, such as cognitive, social and reproductive impairments. Classic galactosemia represents a heavy burden on patients' and their families' lives. After its first description in 1908 and despite intense research in the past century, the exact pathogenic mechanisms underlying galactosemia are still not fully understood. Recently, new important insights on molecular and cellular aspects of galactosemia have been gained, and should open new avenues for the development of novel therapeutic strategies. Moreover, an international galactosemia network has been established, which shall act as a platform for expertise and research in galactosemia. Herein are reviewed some of the latest developments in clinical practice and research findings on classic galactosemia, an enigmatic disorder with many unanswered questions warranting dedicated research.

Systematic Review and Meta-analysis of Intelligence Quotient in Early-Treated Individuals with Classical Galactosemia

INTRODUCTION

Cognitive impairment is a well-known complication of classical galactosemia (CG). Differences in patient characteristics and test methods have hampered final conclusions regarding the extent of intellectual disabilities in CG. The primary aim of this systematic review was to assess intellectual performance in early-treated (≤4 weeks of life) individuals with confirmed CG (defined by absent or barely detectable GALT enzyme activity and/or the presence of two null or severe missense variations), assessed with comparable test instruments. The full-scale IQ (FSIQ) was the variable of interest.

METHODS

A clinical librarian developed search strategies, and two independent investigators performed the study selection, risk of bias assessment and data extraction. Individual patient data were pooled for meta-analysis using linear mixed-effect models with a random intercept per study and including covariates (age or gender) as fixed effects where appropriate.

RESULTS

Four articles were included in this meta-analysis. Data of 87 individuals (median age 13 years, range 3-38 years) were used to assess mean FSIQ in CG. The FSIQ ranged from 47 to 122, and the mean score was 87 (95% CI, 81-94). Forty-five percent of individuals attained scores <85, almost 40% attained scores of 85-100, and a minority (15%) attained scores above 100. There was no significant correlation between FSIQ and age.

CONCLUSIONS

Results from this meta-analysis fortify conclusions from previous studies that early-treated individuals with CG are at risk for having impaired cognitive abilities. However, IQ varies considerably between affected individuals.

Nine years of newborn screening for classical galactosemia in the Netherlands: Effectiveness of screening methods, and identification of patients with previously unreported phenotypes

INTRODUCTION

Newborn screening (NBS) for classical galactosemia (CG) was introduced in the Netherlands in 2007. Multiple screening methods have been used since, and currently a two-tier system is used, with residual enzyme activity of galactose-1-phosphate-uridyltransferase (GALT) and total galactose concentration in dried blood spots as the primary and secondary markers. As it is essential to monitor effectiveness of NBS programs, we assessed the effectiveness of different screening methods used over time (primary aim), and aimed to identify and investigate patients identified through NBS with previously unreported clinical and biochemical phenotypes (secondary aim).

METHODS

The effectiveness of different screening methods and their cut-off values (COVs), as used from 2007 through 2015, was determined, and the clinical and biochemical data of all identified patients were retrospectively collected.

RESULTS

All screening methods and COVs resulted in relatively high false-positive rates and low positive predictive values. Total galactose levels in dried blood spots were far above the COV for NBS in all true positive cases. A total of 31 galactosemia patients were identified, and when corrected for a family with three affected siblings, 14% had a previously unreported phenotype and genotype. These individuals did not demonstrate any symptoms at the time of diagnosis while still being exposed to galactose, had galactose-1-phosphate values below detection limit within months after the start of diet, and had previously unreported genotypes.

CONCLUSION

Optimization of NBS for CG in the Netherlands is warranted because of the high false-positive rate, which may result in significant harm. Furthermore, a surprising 14% of newborns identified with CG by screening had previously unreported clinical and biochemical phenotypes and genotypes. For them, individualized prognostication and treatment are warranted, in order to avoid unnecessary stringent galactose restriction.

Bone Health in Classic Galactosemia: Systematic Review and Meta-Analysis

INTRODUCTION

Previous studies have reported an association between classic galactosemia (CG) and decreased bone mass. The primary objective of this systematic review with meta-analysis was to determine the extent of bone mineral density (BMD) Z-score reduction. Low BMD was defined as a Z-score ≤-2 standard deviations (SD). The secondary objective was to evaluate other indicators of bone status through a descriptive analysis.

METHODS

Systematic search strategies were developed by an experienced clinical librarian. Selection of relevant manuscripts, risk of bias assessment, and data extraction were performed independently by two investigators.

RESULTS

Four studies were included in the meta-analysis. BMD Z-scores in children and adults with CG measured at the lumbar spine (LBMD; 4 studies; n  = 112), total hip (HBMD; 2 studies; n = 58), and femoral neck (FBMD; 2 studies; n = 73) were assessed. Mean BMD Z-scores in the CG population were LBMD -0.70 (95% CI: -0.88, -0.52); HBMD -0.89 (95% CI: -1.14, -0.64); and FBMD -0.63 (95% CI -1.29, 0.02). Results from studies included in the descriptive analysis (n = 7) show that vitamin D levels were frequently in the low reference range, whereas serum calcium levels were within reference range.

CONCLUSION

The mean BMD Z-score in the CG population is -0.7, which is lower than in the general population, though still within two SD of the reference mean of zero. This indicates that bone health is mildly affected in CG and that more patients, compared to the general population, are at risk for a BMD Z-score ≤-2 SD. In conclusion, clinicians should ensure appropriate preventive and therapeutic measures for CG patients.

Appropriateness of newborn screening for classic galactosaemia: a systematic review

Currently, there is no universal agreement on galactosaemia screening, fundamentally because of the risk-benefit uncertainties. We conducted two exhaustive systematic searches in the main electronic databases (PubMed, Embase, Cochrane, etc.) to recover relevant information about the disease and screening test/s in order to support decision making in Spain. All of the 45 studies identified that covered disease issues were retrospective case series or cross-sectional analysis (level-4 evidence). Studies consistently found that the majority of patients presented characteristic symptomatology before diagnosis. Long term disabilities were not significantly correlated with age of diagnosis, onset of dietary restriction or strict diet compliance. The five studies that provided accuracy data used different cut-off points and verification tests, and thus differed in their definitions of a positive case (level-3b evidence). The estimated sensitivity was 100 % and the specificity 99.9 %. The false-positive rate ranged from 0.0005 % to 0.25 %, and the PPV from 0 % to 64.3 %. The comparative clinical effectiveness in relation to not screening or implementation of other programs is unknown. In summary, existing evidence remains insufficient to establish the appropriateness of newborn screening for galactosaemia screening, although health benefits could be expected if early diagnosis and treatment is achieved. If screening is implemented in Spain, it would be important that a pilot programme be implemented to assess false positive rate and ensure that early diagnosis is not delayed.