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.

Organic Aciduria Disorders in Pregnancy: An Overview of Metabolic Considerations

Organic acidurias are a heterogeneous group of rare inherited metabolic disorders (IMDs) caused by a deficiency of an enzyme or a transport protein involved in the intermediary metabolic pathways. These enzymatic defects lead to an accumulation of organic acids in different tissues and their subsequent excretion in urine. Organic acidurias include maple syrup urine disease, propionic aciduria, methylmalonic aciduria, isovaleric aciduria, and glutaric aciduria type 1. Clinical features vary between different organic acid disorders and may present with severe complications. An increasing number of women with rare IMDs are reporting successful pregnancy outcomes. Normal pregnancy causes profound anatomical, biochemical and physiological changes. Significant changes in metabolism and nutritional requirements take place during different stages of pregnancy in IMDs. Foetal demands increase with the progression of pregnancy, representing a challenging biological stressor in patients with organic acidurias as well as catabolic states post-delivery. In this work, we present an overview of metabolic considerations for pregnancy in patients with organic acidurias.

The hypergonadotropic hypogonadism conundrum of classic galactosemia

BACKGROUND

Hypergonadotropic hypogonadism is a burdensome complication of classic galactosemia (CG), an inborn error of galactose metabolism that invariably affects female patients. Since its recognition in 1979, data have become available regarding the clinical spectrum, and the impact on fertility. Many women have been counseled for infertility and the majority never try to conceive, yet spontaneous pregnancies can occur. Onset and mechanism of damage have not been elucidated, yet new insights at the molecular level are becoming available that might greatly benefit our understanding. Fertility preservation options have expanded, and treatments to mitigate this complication either by directly rescuing the metabolic defect or by influencing the cascade of events are being explored.

OBJECTIVE AND RATIONALE

The aims are to review: the clinical picture and the need to revisit the counseling paradigm; insights into the onset and mechanism of damage at the molecular level; and current treatments to mitigate ovarian damage.

SEARCH METHODS

In addition to the work on this topic by the authors, the PubMed database has been used to search for peer-reviewed articles and reviews using the following terms: 'classic galactosemia', 'gonadal damage', 'primary ovarian insufficiency', 'fertility', 'animal models' and 'fertility preservation' in combination with other keywords related to the subject area. All relevant publications until August 2022 have been critically evaluated and reviewed.

OUTCOMES

A diagnosis of premature ovarian insufficiency (POI) results in a significant psychological burden with a high incidence of depression and anxiety that urges adequate counseling at an early stage, appropriate treatment and timely discussion of fertility preservation options. The cause of POI in CG is unknown, but evidence exists of dysregulation in pathways crucial for folliculogenesis such as phosphatidylinositol 3-kinase/protein kinase B, inositol pathway, mitogen-activated protein kinase, insulin-like growth factor-1 and transforming growth factor-beta signaling. Recent findings from the GalT gene-trapped (GalTKO) mouse model suggest that early molecular changes in 1-month-old ovaries elicit an accelerated growth activation and burnout of primordial follicles, resembling the progressive ovarian failure seen in patients. Although data on safety and efficacy outcomes are still limited, ovarian tissue cryopreservation can be a fertility preservation option. Treatments to overcome the genetic defect, for example nucleic acid therapy such as mRNA or gene therapy, or that influence the cascade of events are being explored at the (pre-)clinical level.

WIDER IMPLICATIONS

Elucidation of the molecular pathways underlying POI of any origin can greatly advance our insight into the pathogenesis and open new treatment avenues. Alterations in these molecular pathways might serve as markers of disease progression and efficiency of new treatment options.

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.

Management of pregnancy in a patient with long‐chain 3‐hydroxyacyl CoA dehydrogenase deficiency

Long‐chain 3‐hydroxyacyl‐CoA dehydrogenase deficiency (LCHADD) is a rare mitochondrial defect of β‐oxidation of long‐chain fatty acids. Patients may present with muscle pain, hypotonia, peripheral neuropathy, cardiomyopathy, recurrent rhabdomyolysis and sudden death. Dietary management of LCHADD aims at preventing prolonged fasting and decreasing energy production from long‐chain fatty acids compensated by an increase in medium‐chain triglyceride fat. Herein, we present medical and dietetic management of a successful pregnancy in a LCHADD female patient and the delivery of a healthy baby boy.

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.

Maple syrup urine disease: Clinical outcomes, metabolic control, and genotypes in a screened population after four decades of newborn bloodspot screening in the Republic of Ireland

Since 1972, 18 patients (10 females/8 males) have been detected by newborn bloodspot screening (NBS) with neonatal-onset maple syrup urine disease (MSUD) in Ireland. Patients were stratified into three clusters according to clinical outcome at the time of data collection, including developmental, clinical, and IQ data. A fourth cluster comprised of two early childhood deaths; a third patient died as an adult. We present neuroimaging and electroencephalography together with clinical and biochemical data. Incidence of MSUD (1972-2018) was 1 in 147 975. Overall good clinical outcomes were achieved with 15/18 patients alive and with essentially normal functioning (with only the lowest performing cluster lying beyond a single SD on their full scale intelligence quotient). Molecular genetic analysis revealed genotypes hitherto not reported, including a possible digenic inheritance state for the BCKDHA and DBT genes in one family. Treatment has been based on early implementation of emergency treatment, diet, close monitoring, and even dialysis in the setting of acute metabolic decompensation. A plasma leucine ≥400 μmol/L (outside therapeutic range) was more frequently observed in infancy or during adolescence, possibly due to infections, hormonal changes, or noncompliance. Children require careful management during metabolic decompensations in early childhood, and this represented a key risk period in our cohort. A high level of metabolic control can be achieved through diet with early implementation of a "sick day" regime and, in some cases, dialysis as a rescue therapy. The Irish cohort, despite largely classical phenotypes, achieved good outcomes in the NBS era, underlining the importance of early diagnosis and skilled multidisciplinary team management.

Impact of trimethylaminuria on daily psychosocial functioning

BACKGROUND

Trimethylaminuria (TMAU) (OMIM #602079) is a rare inherited metabolic condition. TMAU is associated with decreased hepatic trimethylamine N-oxidation, which leads to an excess of the volatile trimethylamine (TMA) instead of substrate conversion to trimethylamine N-oxide (TMAO). TMA is a tertiary amine derived from the enterobacterial metabolism of precursors such as choline and phosphatidylcholine present in the diet, and is also a bacterial metabolite of TMAO, a normal constituent of saltwater fish. When the involved enzyme flavin mono-oxygenase 3 is deficient, TMA builds up and is released in the person's sweat, urine, and breath, giving off a strong body odor. We have recently reported the biochemical and genetic characteristics of 13 Irish adult patients with TMAU attending the main Irish Reference Center. Research on the behavioral and psychosocial aspects of this condition is limited. This study explores the patients' perspectives of living with TMAU in Ireland.

METHODS

A qualitative descriptive phenomenological approach was used. Six adults participated in this study. Data were gathered through semi-structured interviews, which were transcribed and analyzed.

RESULTS

The results suggest that the participants experienced a negative journey to diagnosis. Fear, anxiety, paranoia, and dysfunctional thinking are a constant struggle. Participants reported using avoidant coping mechanisms and strategic planning to navigate daily life.

CONCLUSION

It is considered that the results from this study will inform future interventions with this unique patient cohort.

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.

Galactokinase deficiency: lessons from the GalNet registry

PURPOSE

Galactokinase (GALK1) deficiency is a rare hereditary galactose metabolism disorder. Beyond cataract, the phenotypic spectrum is questionable. Data from affected patients included in the Galactosemias Network registry were collected to better characterize the phenotype.

METHODS

Observational study collecting medical data of 53 not previously reported GALK1 deficient patients from 17 centers in 11 countries from December 2014 to April 2020.

RESULTS

Neonatal or childhood cataract was reported in 15 and 4 patients respectively. The occurrence of neonatal hypoglycemia and infection were comparable with the general population, whereas bleeding diathesis (8.1% versus 2.17-5.9%) and encephalopathy (3.9% versus 0.3%) were reported more often. Elevated transaminases were seen in 25.5%. Cognitive delay was reported in 5 patients. Urinary galactitol was elevated in all patients at diagnosis; five showed unexpected Gal-1-P increase. Most patients showed enzyme activities ≤1%. Eleven different genotypes were described, including six unpublished variants. The majority was homozygous for NM_000154.1:c.82C>A (p.Pro28Thr). Thirty-five patients were diagnosed following newborn screening, which was clearly beneficial.

CONCLUSION

The phenotype of GALK1 deficiency may include neonatal elevation of transaminases, bleeding diathesis, and encephalopathy in addition to cataract. Potential complications beyond the neonatal period are not systematically surveyed and a better delineation is needed.

The Galactose Index measured in fibroblasts of GALT deficient patients distinguishes variant patients detected by newborn screening from patients with classical phenotypes

BACKGROUND

The high variability in clinical outcome of patients with Classical Galactosemia (CG) is poorly understood and underlines the importance of prognostic biomarkers, which are currently lacking. The aim of this study was to investigate if residual galactose metabolism capacity is associated with clinical and biochemical outcomes in CG patients with varying geno- and phenotypes.

METHODS

Galactose Metabolite Profiling (GMP) was used to determine residual galactose metabolism in fibroblasts of CG patients. The association between the galactose index (GI) defined as the ratio of the measured metabolites [U¹³C]Gal-1-P/ [¹³C₆]UDP-galactose, and both intellectual and neurological outcome and galactose-1-phosphate (Gal-1-P) levels was investigated.

RESULTS

GMP was performed in fibroblasts of 28 patients and 3 control subjects. The GI of the classical phenotype patients (n = 22) was significantly higher than the GI of four variant patients detected by newborn screening (NBS) (p = .002), two homozygous p.Ser135Leu patients (p = .022) and three controls (p = .006). In the classical phenotype patients, 13/18 (72%) had a poor intellectual outcome (IQ < 85) and 6/12 (50%) had a movement disorder. All the NBS detected variant patients (n = 4) had a normal intellectual outcome (IQ ≥ 85) and none of them has a movement disorder. In the classical phenotype patients, there was no significant difference in GI between patients with a poor and normal clinical outcome. The NBS detected variant patients had significantly lower GI levels and thus higher residual galactose metabolism than patients with classical phenotypes. There was a clear correlation between Gal-1-P levels in erythrocytes and the GI (p = .001).

CONCLUSIONS

The GI was able to distinguish CG patients with varying geno- and phenotypes and correlated with Gal-1-P. The data of the NBS detected variant patients demonstrated that a higher residual galactose metabolism may result in a more favourable clinical outcome. Further research is needed to enable individual prognostication and treatment in all CG patients.

The role of primary care in management of rare diseases in Ireland

Background

‘Slaintecare’ aims to address complex patient care needs in an integrated fashion with an emphasis on patient-centred, patient-empowered community care.Currently there is a lack of knowledge of the impact of rare disease management in primary care and of the information tools required by general practitioners to deliver integrated care for rare disease patients.

Aims

To complete a pilot survey to estimate the general practice clinical workload attributable to selected rare diseases and assess the use of relevant information sources.

Methods

A retrospective cross-sectional survey was carried out of general practice consultations (2013–2017) for patients with 22 commonly recognised rare diseases.

Results

Around 31 general practitioners from 10 Irish practices completed information on 171 patients with rare diseases over 3707 consultations. General practice-specific coding systems were inadequate for rare disease patient identification. Over 139 (81.3%) patients were adult, and 32 (18.7%) were children. Management of care was hospital and not primary care based in 63%. Those eligible for state-reimbursed care had a significantly higher median number of consultations (23 consultations, IQR = 13–37, or 5.8 consultations/year) than those who paid privately (10 consultations, IQR = 4–19, or 2.5 consultations/year) (p < 0.005).General practitioners had access to public information resources on rare diseases but few had knowledge of (35.5%), or had ever used (12.9%) Orphanet, the international rare disease information portal.

Conclusions

Both specific rare disease-specific coding and use of the relevant rare disease information sources are lacking in general practice in Ireland.

Challenges in diagnosing and managing adult patients with urea cycle disorders

Urea cycle disorders (UCD) are a group of rare inherited metabolic conditions of amino acid catabolism caused by an enzyme deficiency within the hepatic ammonia detoxification pathway. The presentation of these disorders ranges from life-threatening intoxication in the neonate to asymptomatic status in adults. Late-onset UCDs can present for the first time in adulthood and may mimic other causes of acute confusion or psychiatric diseases, and are often associated with neurological symptoms. Late-onset UCDs may become apparent during periods of metabolic stress such as rapid weight loss, gastric bypass surgery, chronic starvation or the postpartum period. Early diagnosis is critical for effective treatment and to prevent long-term complications of hyperammonemia. The challenges of management of adults include for example: (a) poor compliance to dietary and medical treatment which can result in recurrent hospital admissions; (b) severe neurological dysfunction; (c) the management of pregnancy and the postpartum period; and (d) access to multidisciplinary care peri-operatively. In this review, we highlight a number of challenges in the diagnosis and management of adult patient with late-onset UCDs and suggest a systematic management approach.

Expanding the genetic and phenotypic spectrum of branched-chain amino acid transferase 2 deficiency

The first step in branched-chain amino acid (BCAA) catabolism is catalyzed by the two BCAA transferase isoenzymes, cytoplasmic branched-chain amino acid transferase (BCAT) 1, and mitochondrial BCAT2. Defects in the second step of BCAA catabolism cause maple syrup urine disease (MSUD), a condition which has been far more extensively investigated. Here, we studied the consequences of BCAT2 deficiency, an ultra-rare condition in humans. We present genetic, clinical, and functional data in five individuals from four different families with homozygous or compound heterozygous BCAT2 mutations which were all detected following abnormal biochemical profile results or familial mutation segregation studies. We demonstrate that BCAT2 deficiency has a recognizable biochemical profile with raised plasma BCAAs and, in contrast with MSUD, low-normal branched-chain keto acids (BCKAs) with undetectable l-allo-isoleucine. Interestingly, unlike in MSUD, none of the individuals with BCAT2 deficiency developed acute encephalopathy even with exceptionally high BCAA levels. We observed wide-ranging clinical phenotypes in individuals with BCAT2 deficiency. While one adult was apparently asymptomatic, three individuals had presented with developmental delay and autistic features. We show that the biochemical characteristics of BCAT2 deficiency may be amenable to protein-restricted diet and that early treatment may improve outcome in affected individuals. BCAT2 deficiency is an inborn error of BCAA catabolism. At present, it is unclear whether developmental delay and autism are parts of the variable phenotypic spectrum of this condition or coincidental. Further studies will be required to explore this.

The genetic and biochemical basis of trimethylaminuria in an Irish cohort

BACKGROUND

Inherited trimethylaminuria (TMAU), a rare genetic disorder of hepatic metabolism of trimethylamine (TMA) causing excessive accumulation of malodorous trimethylamine (TMA), is a socially distressing disorder. Diagnosis is made by biochemical analysis of urine, with the calculation of flavin monooxygenase trimethylamine conversion capacity. Genetic testing, sequencing the entire coding region of the FMO3 gene has been recommended for affected individuals who convert less than 90% of the total TMA load to TMAO.

METHODS

Genetic analysis was undertaken for 13 Irish patients with TMAU of varying phenotypic severity (three severe, six moderate, and four mild).

RESULTS

A genetic diagnosis was made for seven patients, including for five of the nine moderate to severely affected cases. We noted the c.913G>T;p.(Glu305*) and c.458C>T;p.(Pro153Leu) mutations in this Irish population with severe TMAU which is consistent with our earlier findings in Australian and North American families of Irish and British descent.Three individuals were noted to be homozygous for the common variant haplotype c.472G>A;923A>G;p.(Glu158Lys);(Glu308Gly). We also identified three novel variants in this population, which are likely to be pathogenic: c.682G>A;p(Gly228Ser), c.694G>T:p(Asp232Tyr), and c.989G>A;p.(Gly330Glu).

CONCLUSION

Urinary biochemical analysis probably remains the first line diagnostic approach to classify the various types of TMAU. FMO3 gene analysis is likely only to be informative for certain presentations of TMAU.

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.

Long-term outcomes in a 25-year-old female affected with lipin-1 deficiency

Lipin-1 is a phosphatidic acid phosphohydrolase (EC 3.1.3.4) that catalyzes the dephosphorylation of phosphatidic acid to diacylglycerol and inorganic phosphate. Deficiency of this enzyme causes potentially fatal severe, recurrent episodes of rhabdomyolysis triggered by infection. The defect has only recently been recognized so little is known about the long-term outcome in adult patients with this disorder. We report the course and outcome of a 25-year-old female patient with lipin-1 deficiency after a recent episode of rhabdomyolysis requiring intensive care admission with a peak creatine kinase of 500 000 IU/L. One-year post discharge from intensive care, the patient has residual drop foot bilaterally consistent with bilateral common peroneal neuropathies in addition to a background residual distal myopathy.

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.

Neurocognitive assessments and long-term outcome in an adult with 2-methyl-3-hydroxybutyryl-CoA dehydrogenase deficiency

Background

2-Methyl-3-hydroxybutyryl-CoA dehydrogenase deficiency (MHBDD) is a rare X-linked disorder associated with the accumulation of 2-methyl-3-hydroxybutyric acid in body fluids as a consequence of a disruption in isoleucine metabolism. The clinical presentation is heterogeneous, including a neurodegenerative course with retinopathy and cardiomyopathy leading to death in early childhood and a slowly progressive disease associated with learning disability and survival into adulthood. The condition is often diagnosed in childhood.

Results

This paper outlines the long-term neurocognitive outcomes in a 38-year old man with MHBDD. Several psychometric tests were used to assess his cognitive ability and adaptive functioning in childhood during an acute illness and in adulthood when the patient showed deterioration in the ability to walk or speak.

Conclusions

There is an increasing demand for an accurate and objective measure of cognitive functioning that can be used to follow the natural progression of MHBDD. Psychological assessment may enable the identification of organic problems. The application and interpretation of psychometric tests used in children may vary from those used in adults.

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.

International clinical guideline for the management of classical galactosemia: diagnosis, treatment, and follow-up

Classical galactosemia (CG) is an inborn error of galactose metabolism. Evidence-based guidelines for the treatment and follow-up of CG are currently lacking, and treatment and follow-up have been demonstrated to vary worldwide. To provide patients around the world the same state-of-the-art in care, members of The Galactosemia Network (GalNet) developed an evidence-based and internationally applicable guideline for the diagnosis, treatment, and follow-up of CG. The guideline was developed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system. A systematic review of the literature was performed, after key questions were formulated during an initial GalNet meeting. The first author and one of the working group experts conducted data-extraction. All experts were involved in data-extraction. Quality of the body of evidence was evaluated and recommendations were formulated. Whenever possible recommendations were evidence-based, if not they were based on expert opinion. Consensus was reached by multiple conference calls, consensus rounds via e-mail and a final consensus meeting. Recommendations addressing diagnosis, dietary treatment, biochemical monitoring, and follow-up of clinical complications were formulated. For all recommendations but one, full consensus was reached. A 93 % consensus was reached on the recommendation addressing age at start of bone density screening. During the development of this guideline, gaps of knowledge were identified in most fields of interest, foremost in the fields of treatment and follow-up.

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.

Classical Galactosaemia and CDG, the N-Glycosylation Interface. A Review

Classical galactosaemia is a rare disorder of carbohydrate metabolism caused by galactose-1-phosphate uridyltransferase (GALT) deficiency (EC 2.7.7.12). The disease is life threatening if left untreated in neonates and the only available treatment option is a long-term galactose restricted diet. While this is lifesaving in the neonate, complications persist in treated individuals, and the cause of these, despite early initiation of treatment, and shared GALT genotypes remain poorly understood. Systemic abnormal glycosylation has been proposed to contribute substantially to the ongoing pathophysiology. The gross N-glycosylation assembly defects observed in the untreated neonate correct over time with treatment. However, N-glycosylation processing defects persist in treated children and adults.Congenital disorders of glycosylation (CDG) are a large group of over 100 inherited disorders affecting largely N- and O-glycosylation.In this review, we compare the clinical features observed in galactosaemia with a number of predominant CDG conditions.We also summarize the N-glycosylation abnormalities, which we have described in galactosaemia adult and paediatric patients, using an automated high-throughput HILIC-UPLC analysis of galactose incorporation into serum IgG with analysis of the corresponding N-glycan gene expression patterns and the affected pathways.

Clinical and genetic characterisation of infantile liver failure syndrome type 1, due to recessive mutations in LARS

BACKGROUND

Recessive LARS mutations were recently reported to cause a novel syndrome, infantile liver failure syndrome type 1 (ILFS1), in six Irish Travellers. We have since identified four additional patients, including one of Ashkenazi origin, representing the largest ILFS1 cohort to date. Our study aims to define the ILFS1 clinical phenotype to help guide diagnosis and patient management.

METHODS

We clinically evaluated and reviewed the medical records of ten ILFS1 patients. Clinical features, histopathology and natural histories were compared and patient management strategies reviewed.

RESULTS

Early failure to thrive, recurrent liver dysfunction, anemia, hypoalbuminemia and seizures were present in all patients. Most patients (90 %) had developmental delay. Encephalopathic episodes triggered by febrile illness have occurred in 80 % and were fatal in two children. Two patients are currently >28 years old and clinically well. Leucine supplementation had no appreciable impact on patient well-being. However, we suggest that the traditional management of reducing/stopping protein intake in patients with metabolic hepatopathies may not be appropriate for ILFS1. We currently recommend ensuring sufficient natural protein intake when unwell.

CONCLUSIONS

We report the first non-Irish ILFS1 patient, suggesting ILFS1 may be more extensive than anticipated. Low birth weight, early failure to thrive, anemia and hypoalbuminemia are amongst the first presenting features, with liver dysfunction before age 1. Episodic hepatic dysfunction is typically triggered by febrile illness, and becomes less severe with increasing age. While difficult to anticipate, two patients are currently >28 years old, suggesting that survival beyond childhood may be associated with a favourable long-term prognosis.

Systemic gene dysregulation in classical Galactosaemia: Is there a central mechanism?

Classical Galactosaemia is a rare disorder of carbohydrate metabolism caused by a deficiency of galactose-1-phosphate uridyltransferase (GALT). The disease is life-threatening in the neonate, and the only treatment option is life-long dietary restriction of galactose. However, long-term complications persist in treated patients including cognitive impairments, speech and language abnormalities and premature ovarian insufficiency in females. Microarray analysis of T-lymphocytes from treated adult patients identified systemic dysregulation of numerous gene pathways, including the glycosylation, inflammatory and inositol pathways. Analysis of gene expression in patient-derived dermal fibroblasts of patients exposed to toxic levels of galactose, with immunostaining, has further identified the susceptibility of the glycosylation gene alpha-1,2-mannosyltransferase (ALG9) and the inflammatory gene annexin A1 (ANXA1) to increased galactose concentrations. These data suggest that Galactosaemia is a multi-system disorder affecting numerous signalling pathways.

Fertility preservation in female classic galactosemia patients

Almost every female classic galactosemia patient develops primary ovarian insufficiency (POI) as a diet-independent complication of the disease. This is a major concern for patients and their parents, and physicians are often asked about possible options to preserve fertility. Unfortunately, there are no recommendations on fertility preservation in this group. The unique pathophysiology of classic galactosemia with a severely reduced follicle pool at an early age requires an adjusted approach. In this article recommendations for physicians based on current knowledge concerning galactosemia and fertility preservation are made. Fertility preservation is only likely to be successful in very young prepubertal patients. In this group, cryopreservation of ovarian tissue is currently the only available technique. However, this technique is not ready for clinical application, it is considered experimental and reduces the ovarian reserve. Fertility preservation at an early age also raises ethical questions that should be taken into account. In addition, spontaneous conception despite POI is well described in classic galactosemia. The uncertainty surrounding fertility preservation and the significant chance of spontaneous pregnancy warrant counseling towards conservative application of these techniques. We propose that fertility preservation should only be offered with appropriate institutional research ethics approval to classic galactosemia girls at a young prepubertal age.

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

Newborn screening for the inborn error of metabolism, classical galactosaemia prevents life-threatening complications in the neonatal period. It does not however influence the development of long-term complications and the complex pathophysiology of this rare disease remains poorly understood. The objective of this study was to report the development of a healthcare database (using Distiller Version 2.1) to review the epidemiology of classical galactosaemia in Ireland since initiation of newborn screening in 1972 and the long-term clinical outcomes of all patients attending the National Centre for Inherited Metabolic Disorders (NCIMD). Since 1982, the average live birth incidence rate of classical galactosaemia in the total Irish population was approximately 1:16,476 births. This reflects a high incidence in the Irish 'Traveller' population, with an estimated birth incidence of 1:33,917 in the non-Traveller Irish population. Despite early initiation of treatment (dietary galactose restriction), the long-term outcomes of classical galactosaemia in the Irish patient population are poor; 30.6 % of patients ≥ 6 yrs have IQs <70, 49.6 % of patients ≥ 2.5 yrs have speech or language impairments and 91.2 % of females ≥ 13 yrs suffer from hypergonadotrophic hypogonadism (HH) possibly leading to decreased fertility. These findings are consistent with the international experience. This emphasizes the requirement for continued clinical research in this complex disorder.

Capturing phenotypic heterogeneity in MPS I: results of an international consensus procedure

Background

Mucopolysaccharidosis type I (MPS I) is traditionally divided into three phenotypes: the severe Hurler (MPS I-H) phenotype, the intermediate Hurler-Scheie (MPS I-H/S) phenotype and the attenuated Scheie (MPS I-S) phenotype. However, there are no clear criteria for delineating the different phenotypes. Because decisions about optimal treatment (enzyme replacement therapy or hematopoietic stem cell transplantation) need to be made quickly and depend on the presumed phenotype, an assessment of phenotypic severity should be performed soon after diagnosis. Therefore, a numerical severity scale for classifying different MPS I phenotypes at diagnosis based on clinical signs and symptoms was developed.

Methods

A consensus procedure based on a combined modified Delphi method and a nominal group technique was undertaken. It consisted of two written rounds and a face-to-face meeting. Sixteen MPS I experts participated in the process. The main goal was to identify the most important indicators of phenotypic severity and include these in a numerical severity scale. The correlation between the median subjective expert MPS I rating and the scores derived from this severity scale was used as an indicator of validity.

Results

Full consensus was reached on six key clinical items for assessing severity: age of onset of signs and symptoms, developmental delay, joint stiffness/arthropathy/contractures, kyphosis, cardiomyopathy and large head/frontal bossing. Due to the remarkably large variability in the expert MPS I assessments, however, a reliable numerical scale could not be constructed. Because of this variability, such a scale would always result in patients whose calculated severity score differed unacceptably from the median expert severity score, which was considered to be the 'gold standard'.

Conclusions

Although consensus was reached on the six key items for assessing phenotypic severity in MPS I, expert opinion on phenotypic severity at diagnosis proved to be highly variable. This subjectivity emphasizes the need for validated biomarkers and improved genotype-phenotype correlations that can be incorporated into phenotypic severity assessments at diagnosis.

Reversible infantile respiratory chain deficiency is a unique, genetically heterogenous mitochondrial disease

OBJECTIVES

Homoplasmic maternally inherited, m.14674T>C or m. 14674T>G mt-tRNA(Glu) mutations have recently been identified in reversible infantile cytochrome c oxidase deficiency (or 'benign COX deficiency'). This study sought other genetic defects that may give rise to similar presentations.

PATIENTS

Eight patients from seven families with clinicopathological features of infantile reversible cytochrome c oxidase deficiency were investigated.

METHODS

The study reviewed the diagnostic features and performed molecular genetic analyses of mitochondrial DNA and nuclear encoded candidate genes.

RESULTS

Patients presented with subacute onset of profound hypotonia, feeding difficulties and lactic acidosis within the first months of life. Although recovery was remarkable, a mild myopathy persisted into adulthood. Histopathological findings in muscle included increased lipid and/or glycogen content, ragged-red and COX negative fibres. Biochemical studies suggested more generalised abnormalities than pure COX deficiency. Clinical improvement was reflected by normalisation of lactic acidosis and histopathological abnormalities. The m.14674T>C mt-tRNA(Glu) mutation was identified in four families, but none had the m. 14674T>G mutation. Furthermore, in two families pathogenic mutations were also found in the nuclear TRMU gene which has not previously been associated with this phenotype. In one family, the genetic aetiology still remains unknown.

CONCLUSIONS

Benign COX deficiency is better described as 'reversible infantile respiratory chain deficiency'. It is genetically heterogeneous, and patients not carrying the m.14674T>C or T>G mt-tRNA(Glu) mutations may have mutations in the TRMU gene. Diagnosing this disorder at the molecular level is a significant advance for paediatric neurologists and intensive care paediatricians, enabling them to select children with an excellent prognosis for continuing respiratory support from those with severe mitochondrial presentation in infancy.

IgG N-glycans as potential biomarkers for determining galactose tolerance in Classical Galactosaemia

N-glycan processing and assembly defects have been demonstrated in untreated and partially treated patients with Classical Galactosaemia. These defects may contribute to the ongoing pathophysiology of this disease. The aim of this study was to develop an informative method of studying differential galactose tolerance levels and diet control in individuals with Galactosaemia, compared to the standard biochemical markers. Ten Galactosaemia adults with normal intellectual outcomes were analyzed in the study. Five subjects followed galactose liberalization, increments of 300 mg to 4000 mg/day over 16 weeks, and were compared to five adult Galactosaemia controls on a galactose restricted diet. All study subjects underwent clinical and biochemical monitoring of red blood cell galactose-1-phosphate (RBC Gal-1-P) and urinary galactitol levels. Serum N-glycans were isolated and analyzed by normal phase high-performance liquid chromatography (NP-HPLC) with galactosylation of IgG used as a specific biomarker of galactose tolerance. IgG N-glycan profiles showed consistent individual alterations in response to diet liberalization. The individual profiles were improved for all, but one study subject, at a galactose intake of 1000 mg/day, with decreases in agalactosylated (G0) and increases in digalactosylated (G2) N-glycans. We conclude that IgG N-glycan profiling is an improved method of monitoring variable galactosylation and determining individual galactose tolerance in Galactosaemia compared to the standard methods.

"Stiff neonate" with mitochondrial DNA depletion and secondary neurotransmitter defects

Mitochondrial disorders comprise a heterogenous group. A neonate who presented with episodes of severe truncal hypertonia and apnea progressed to a hypokinetic rigid syndrome characterized by hypokinesia, tremulousness, profound head lag, absent suck and gag reflexes, brisk deep tendon reflexes, ankle and jaw clonus, and evidence of autonomic dysfunction. Analysis of cerebrospinal fluid neurotransmitters from age 7 weeks demonstrated low levels of amine metabolites (homovanillic acid and 5-hydroxyindoleacetic acid), tetrahydrobiopterin, and pyridoxal phosphate. Mitochondrial DNA quantitative studies on muscle homogenate demonstrated a mitochondrial DNA depletion disorder. Respiratory chain enzymology demonstrated decreased complex IV activity. Screening for mitochondrial DNA rearrangement disorders and sequencing relevant mitochondrial genes produced negative results. No clinical or biochemical response to treatment with pyridoxal phosphate, tetrahydrobiopterin, or l-dopa occurred. The clinical course was progressive, and the patient died at age 19 months. Mitochondrial disorders causing secondary neurotransmitter diseases are usually severe, but are rarely reported. This diagnosis should be considered in neonates or infants who present with hypertonia, hypokinesia rigidity, and progressive neurodegeneration.

Should children with inherited metabolic disorders receive varicella vaccination?

The aim was to determine the rate of varicella infection and complications in children with disorders of intermediary metabolism (IEM) between the ages of 1 and 16 years attending our national metabolic referral centre. Of 126 children identified, a response was received from 122. A history of previous varicella infection was identified in 64 cases (53%) and of varicella vaccination in 5 (4%). Fifty-three (43%) patients apparently did not have a history of clinical varicella infection. Of the 64 children with a history of varicella infection, five required hospitalisation for complications, including life-threatening lactic acidosis in one patient with mitochondrial disease and metabolic decompensation in four patients. In conclusion, varicella infection may cause an increased risk of metabolic decompensation in patients with IEMs. We propose that a trial of varicella vaccination be considered for this cohort of patients with monitoring of its safety and efficacy.

Glycogen storage disease type III in the Irish population

Glycogen storage disease type III (GSD III) results from mutations of the AGL gene encoding the glycogen debrancher enzyme. The disease has clinical and biochemical heterogeneity reflecting the severity of the AGL mutations. We sought to characterise the molecular defects in our cohort of Irish patients with GSD III. Fifteen patients from eight unrelated Irish families were identified: six males and nine females. The age ranged from 2-39 years old, and all presented in the first 3 years of life. Four patients (of three families) had mild disease with hepatomegaly, mild hypoglycaemia and normal creatine kinase (CK) levels. Five families had more severe disease, with liver and skeletal muscle involvement and elevated CK. Eleven different mutations were identified amongst the eight families. Of the 11, six were novel: p.T512fs, p.S736fs, p.A1400fs, p.K1407fs, p.Y519X and p.D627Y. The family homozygous for p.A1400fs had the most severe phenotype (early-onset hypoglycaemia, massive hepatomegaly, myopathy and hypertrophic cardiomyopathy before age 2 years), which was not halted by aggressive carbohydrate and protein supplementation. Conversely, the only missense mutation identified in the cohort, p.D627Y, was associated with a mild phenotype. The phenotypic diversity in our GSD III cohort is mirrored by the allelic heterogeneity. We describe two novel null mutations in exon 32 in two families with severe GSD III resistant to current treatment modalities. Knowledge of the specific mutations segregating in this cohort may allow for the development of new therapeutic interventions.

Galactosemia, a single gene disorder with epigenetic consequences

Long-term outcomes of classic galactosemia (GAL) remain disappointing. It is unclear if the complications result mainly from prenatal-neonatal toxicity or persistent glycoprotein and glycolipid synthesis abnormalities. We performed gene expression profiling (T transcriptome) to characterize key-altered genes and gene clusters of four patients with GAL with variable outcomes maintained on a galactose-restricted diet, compared with controls. Significant perturbations of multiple cell signaling pathways were observed including mitogen-activated protein kinase (MAPK) signaling, regulation of the actin cytoskeleton, focal adhesion, and ubiquitin mediated proteolysis. A number of genes significantly altered were further investigated in the GAL cohort including SPARC (osteonectin) and S100A8 (S100 calcium-binding protein). The whole serum N-glycan profile and IgG glycosylation status of 10 treated patients with GAL were compared with healthy control serum and IgG using a quantitative high-throughput analytical HPLC platform. Increased levels of agalactosylated and monogalactosylated structures and decreases in certain digalactosylated structures were identified in the patients. The persistent abnormal glycosylation of serum glycoproteins seen with the microarray data indicates persisting metabolic dyshomeostasis and gene dysregulation in "treated" GAL. Strict restriction of dietary galactose is clearly life saving in the neonatal period; long-term severe galactose restriction may contribute to ongoing systemic abnormalities.

Negative screening tests in classical galactosaemia caused by S135L homozygosity

Classical galactosaemia is relatively common in Ireland due to a high carrier rate of the Q188R GALT mutation. It is screened for using a bacterial inhibition assay (BIA) for free galactose. A Beutler assay on day one of life is performed only in high risk cases (infants of the Traveller community and relatives of known cases). A 16-month-old Irish-born boy of Nigerian origin was referred for investigation of developmental delay, and failure to thrive. He had oral aversion to solids and his diet consisted of cow's milk and milk-based cereal mixes. He was found to have microcephaly, weight <2nd percentile, hepatomegaly and bilateral cataracts. Coagulation screen was normal and transaminases were slightly elevated. His original newborn screen was reviewed and confirmed to have been negative; urinary reducing substances on three separate occasions were negative. Beutler assay demonstrated "absent" red cell galactose-1-phosphate uridyltransferase (GALT) activity. GALT enzyme activity was <0.5 gsubs/h per gHb confirming classical galactosaemia. Gal-1-P was elevated at 1.88 micromol/gHb. Mutation analysis of the GALT gene revealed S135L homozygosity. S135L/S135L galactosaemia is associated with absent red cell GALT activity but with approximately 10% activity in other tissues such as the liver and intestines, probably explaining the negative screening tests and the somewhat milder phenotype associated with this genotype. The patient was commenced on galactose-restricted diet; on follow-up at 2 years of age, growth had normalized but there was global developmental delay. In conclusion, galactosaemia must be considered in children who present with poor growth, hepatomegaly, developmental delay and cataracts and GALT enzyme analysis should be a first line test in such cases. Non-enzymatic screening methods such as urinary reducing substances and BIA for free galactose are not reliable in S135L homozygous galactosaemia.

Outcomes of siblings with classical galactosemia

OBJECTIVES

To determine the long-term outcome of dietary intervention in siblings from 14 Irish families with classical galactosemia (McKusick 230400), an autosomal recessive disorder of carbohydrate metabolism and galactose-1-phosphate uridyltransferase (GALT) deficiency.

STUDY DESIGN

Outcomes in siblings on dietary galactose restriction were studied to evaluate whether birth order (ie, time of commencement of diet) and compliance with lactose-restricted diet (galactose intake > or < 20 mg /day), assessed by dietary recall and biochemical monitoring of galactose-1-phosphate [Gal-1-P] and galactitol values, affected outcomes. The outcome variables assessed were IQ, speech, and language assessment scores, neurologic examination results, and magnetic resonance imaging (MRI) of the brain.

RESULTS

There was a high incidence of complications in the overall group, particularly speech and language delay (77%) and low IQ (71%). There was no significant difference in outcome between earlier-treated and later-treated siblings or any correlation with mean Gal-1-P or galactitol values. In most cases, cerebral white matter disease was evident on MRI scanning, with evidence of progressive cerebellar degeneration seen in 2 highly compliant families.

CONCLUSION

The subjects with a higher galactose intake did not exhibit an increased incidence of complications; conversely, those who were very compliant with dietary restrictions did not have more favorable outcomes.

Incidence and prevalence of mucopolysaccharidosis type 1 in the Irish republic

Mucopolysaccharidosis type 1 (MPS1) is an autosomal recessive disorder with severe, moderate and mild phenotypes: Hurler, Hurler-Scheie and Scheie syndromes. We estimated incidence (2001-2006) and prevalence (2002 census) of MPS1 in the Irish Republic (ROI) using population data, database and chart review of all live MPS1 patients attending two specialised centres. Patient genotypes, ethnicity, province of origin, age at diagnosis and presenting features were recorded. Thirty-one patients (14 females, 17 males) were alive, 27 of whom were <15 years. Twenty-six patients had Hurler syndrome, four had Hurler-Scheie and one had Scheie syndrome. The birth incidence was 1 in 26 206 births with a carrier frequency of 1 in 81. Of note, 19/26 (73%) Hurler patients were Irish Travellers. Amongst Irish Travellers the incidence was 1 in 371 with a carrier frequency of 1 in 10. This is the highest recorded incidence worldwide. Given the morbidity and mortality associated with delayed treatment we recommend targeted newborn screening for this population.

Sensory-motor polyneuropathy occurring in variant maple syrup urine disease

Maple syrup urine disease (MSUD; OMIM 248600) results from an inherited deficiency of the branched-chain ketoacid dehydrogenase (BCKD) complex. Approximately 20% of patients with BCKD deficiency are non-classic variants of MSUD with differing clinical severity. Outcomes for this cohort are generally favourable; episodes of metabolic decompensation do not appear to correlate with adverse events if acute management is promptly provided. A case of predominantly axonal sensory-motor neuropathy following metabolic decompensation which persisted for a number of months is presented in an adolescent girl with variant (intermediate type) MSUD. EMG and nerve conduction studies suggested a pre-existent asymptomatic chronic neuropathy, exacerbated by the acute decompensation. Peak leucine concentration at decompensation was 1083 μmol/L. The patient had laboratory signs of secondary mitochondrial respiratory chain dysfunction at presentation. She had been on a moderate dose of thiamine prior to decompensation; thiamine and pyridoxine blood concentrations were normal. This, to our knowledge, is the first report of a neuropathy presenting in a patient with a decompensation of variant MSUD. We propose that this presentation resembles the intermittent neuropathy observed in pyruvate dehydrogenase deficiency and may reflect secondary inhibition of pyruvate dehydrogenase activity by MSUD metabolites.

Safety and efficacy of 22 weeks of treatment with sapropterin dihydrochloride in patients with phenylketonuria

Phenylketonuria (PKU) is an inherited metabolic disease characterized by phenylalanine (Phe) accumulation, which can lead to neurocognitive and neuromotor impairment. Sapropterin dihydrochloride, an FDA-approved synthetic formulation of tetrahydrobiopterin (6R-BH4, herein referred to as sapropterin) is effective in reducing plasma Phe concentrations in patients with hyperphenylalaninemia due to tetrahydrobiopterin (BH4)-responsive PKU, offering potential for improved metabolic control. Eighty patients, > or =8 years old, who had participated in a 6-week, randomized, placebo-controlled study of sapropterin, were enrolled in this 22-week, multicenter, open-label extension study comprising a 6-week forced dose-titration phase (5, 20, and 10 mg/kg/day of study drug consecutively for 2 weeks each), a 4-week dose-analysis phase (10 mg/kg/day), and a 12-week fixed-dose phase (patients received doses of 5, 10, or 20 mg/kg/day based on their plasma Phe concentrations during the dose titration). Dose-dependent reductions in plasma Phe concentrations were observed in the forced dose-titration phase. Mean (SD) plasma Phe concentration decreased from 844.0 (398.0) micromol/L (week 0) to 645.2 (393.4) micromol/L (week 10); the mean was maintained at this level during the study's final 12 weeks (652.2 [382.5] micromol/L at week 22). Sixty-eight (85%) patients had at least one adverse event (AE). All AEs, except one, were mild or moderate in severity. Neither the severe AE nor any of the three serious AEs was considered related to sapropterin. No AE led to treatment discontinuation. Sapropterin is effective in reducing plasma Phe concentrations in a dose-dependent manner and is well tolerated at doses of 5-20 mg/kg/day over 22 weeks in BH4-responsive patients with PKU.

Reversible multiorgan system involvement in a neonate with complex IV deficiency

Mitochondrial respiratory chain deficiencies can present as fulminant liver failure or disease, and the prognosis when associated with severe neonatal lactic acidosis is frequently guarded. We report the case of a neonate who presented with acute liver failure and fulminant lactic acidosis with profound complex IV deficiency documented in muscle and liver biopsies. The neonate subsequently experienced clinical resolution by 3 months of age, and was observed to have reversibility of the biochemical deficiency noted in muscle. This case illustrates that resolution of this severe neonatal phenotype does occur, of importance for accurate prognostic and genetic counseling for such affected neonates.

Further pitfalls in the diagnosis of mtDNA mutations: homoplasmic mt-tRNA mutations

BACKGROUND

Mitochondrial DNA (mtDNA) mutations are important causes of human genetic disease, with mutations in tRNA genes particularly prevalent. In many patients, mutations are heteroplasmic, affecting a population of mtDNA molecules. Establishing the pathogenicity of homoplasmic mitochondrial tRNA (mt-tRNA) mutations, in which the mutation is present in every mtDNA molecule, is extremely difficult. These mutations must conform to specific pathogenic criteria, documenting unequivocally a functional defect of the mutant mt-tRNA.

AIMS

To investigate the pathogenic nature of two homoplasmic mt-tRNA(Thr) deletions, m.15940delT (previously reported as pathogenic) and m.15937delA, by assessing the steady state levels of the mutant mt-tRNA in tissue and cell-line samples from six unrelated families, in which affected individuals were thoroughly investigated for mitochondrial DNA disease on the basis of clinical presentations. Rates of de novo mitochondrial protein synthesis were also examined in control and m.15937delA mutant fibroblasts.

RESULTS

Our data strongly suggest that both single nucleotide deletions are neutral polymorphisms; no obvious defects were apparent in either steady state mt-tRNA(Thr) levels or rates of mitochondrial protein synthesis.

CONCLUSIONS

These findings have important implications for the investigation of other families with suspected mtDNA disease, in particular the requirement to fulfil strict and established pathogenic criteria in order to avoid misattribution of pathogenicity to mt-tRNA variants.

Long chain fatty acid oxidation defects in children: importance of detection and treatment options

BACKGROUND

Mitochondrial beta oxidation plays a major role in energy production. Long chain fatty acid oxidation defects include deficiency of the trifunctional protein (rare) or more commonly defects of the long chain 3-hydroxy acyl-CoA dehydrogenase enzyme (LCHAD). These long chain defects have variable presentations, they may present in the neonate or infant with sudden death, hepatopathy (Reyes disease), hypoketotic hypoglycaemia, rhabdomyolysis, myopathy, cardiomyopathy and with late complications such as peripheral neuropathy, pigmentary retinopathy, retinal degeneration and progressive visual loss. The correct diagnosis at presentation is not only life saving but also allows for the appropriate dietary and other intervention, which may have major effects on outcome.

AIM

Three case reports of patients with long chain fatty acid oxidation defects who have shown significant benefits from treatment are reported.

CONCLUSIONS

These paediatric presentations illustrate the clinical heterogeneity of long chain fatty acid oxidation defects and opportunities for effective management if correctly diagnosed.

Mitochondrial cytopathies, phenotypic heterogeneity and a high incidence

Mitochondrial respiratory chain disorders account for significant and varied presentations in paediatric practice. The true prevalence of these disorders in the paediatric population is still not well documented with predicted geographic variation. We report a retrospective analysis over a seven year period of cases presenting to a tertiary care centre and associated clinical features. The overall prevalence of mitochondrial disorders in our population is higher than expected (1/9,000 births), explained in part by multiple presentations in a consanguineous subgroup of the population (Irish travellers).

Polymorphisms of the Flavin containing monooxygenase 3 (FMO3) gene do not predispose to essential hypertension in Caucasians

BACKGROUND

The recessive disorder trimethylaminuria is caused by defects in the FMO3 gene, and may be associated with hypertension. We investigated whether common polymorphisms of the FMO3 gene confer an increased risk for elevated blood pressure and/or essential hypertension.

METHODS

FMO3 genotypes (E158K, V257M, E308G) were determined in 387 healthy subjects with ambulatory systolic and diastolic blood pressure measurements, and in a cardiovascular disease population of 1649 individuals, 691(41.9%) of whom had a history of hypertension requiring drug treatment. Haplotypes were determined and their distribution noted.

RESULTS

There was no statistically significant association found between any of the 4 common haplotypes and daytime systolic blood pressure in the healthy population (p = 0.65). Neither was a statistically significant association found between the 4 common haplotypes and hypertension status among the cardiovascular disease patients (p = 0.80).

CONCLUSION

These results suggest that the variants in the FMO3 gene do not predispose to essential hypertension in this population.

Coats' plus: a progressive familial syndrome of bilateral Coats' disease, characteristic cerebral calcification, leukoencephalopathy, slow pre- and post-natal linear growth and defects of bone marrow and integument

In 1988 we reported two sisters with bilateral Coats' disease, sparse hair, dystrophic nails, and primeval splashes of intracranial calcification. We now provide an update on this family documenting the occurrence of skeletal defects comprising abnormal bone marrow, osteopenia, and sclerosis with a tendency to fractures, a mixed cerebellar and extrapyramidal movement disorder, infrequent epileptic seizures, leukodystrophic changes, and postnatal growth failure. Additionally, we present two previously unreported individuals from Ireland and Switzerland with the identical disorder which we designate Coats' plus. Since our original publication a number of other authors have described, frequently as a "new" syndrome, cases with a variable combination of the same features observed in our patients. We review this literature and suggest that the phenotypic overlap with dyskeratosis congenita may provide a clue to the molecular aetiology of this multisystem disorder.