Early cataract formation due to galactokinase deficiency: impact of newborn screening

Phenotypic and genetic spectra of galactose mutarotase deficiency: A nationwide survey conducted in Japan

PURPOSE

Galactose mutarotase (GALM) deficiency was first reported in 2019 as the fourth type of galactosemia. This study aimed to investigate the clinical and genotypic spectra of GALM deficiency.

METHODS

This was a questionnaire-based retrospective survey conducted in Japan between February 2022 and March 2023.

RESULTS

We identified 40 patients with GALM deficiency in Japan (estimated prevalence: 1:181,835). Four of 38 patients (10.5%) developed cataracts, which resolved with lactose restriction in 3 out of 4 patients. Transient transaminitis was the most common symptom (23.1%). All of the patients followed lactose restriction; discontinuation of the restriction after infancy did not cause any complications. Moreover, none of the participants experienced long-term complications. Two variants, GALM NM_138801.3: c.294del and c.424G>A, accounted for 72.5% of the identified pathogenic variants. The patients showed moderately elevated blood galactose levels with lactose intake; however, the elevation was lower than that observed in galactokinase deficiency.

CONCLUSION

GALM deficiency is characterized by a similar but milder phenotype and lower blood galactose elevation than in galactokinase deficiency. Diagnosis and initiation of lactose restriction in early infancy should be essential for prevention of cataracts, especially in cases of irreversible opacity.

Whole Exome Sequencing of 20 Spanish Families: Candidate Genes for Non-Syndromic Pediatric Cataracts

Non-syndromic pediatric cataracts are defined as opacification of the crystalline lens that occurs during the first years of life without affecting other organs. Given that this disease is one of the most frequent causes of reversible blindness in childhood, the main objective of this study was to propose new responsible gene candidates that would allow a more targeted genetic approach and expand our genetic knowledge about the disease. We present a whole exome sequencing (WES) study of 20 Spanish families with non-syndromic pediatric cataracts and a previous negative result on an ophthalmology next-generation sequencing panel. After ophthalmological evaluation and collection of peripheral blood samples from these families, WES was performed. We were able to reach a genetic diagnosis in 10% of the families analyzed and found genes that could cause pediatric cataracts in 35% of the cohort. Of the variants found, 18.2% were classified as pathogenic, 9% as likely pathogenic, and 72.8% as variants of uncertain significance. However, we did not find conclusive results in 55% of the families studied, which suggests further studies are needed. The results of this WES study allow us to propose LONP1, ACACA, TRPM1, CLIC5, HSPE1, ODF1, PIKFYVE, and CHMP4A as potential candidates to further investigate for their role in pediatric cataracts, and AQP5 and locus 2q37 as causal genes.

Natural Antioxidant Activities of Plants in Preventing Cataractogenesis

A cataract is a condition that causes 17 million people to experience blindness and is the most significant cause of vision loss, around 47.9%. The formation of cataracts is linked to both the production of reactive oxygen species (ROS) and the reduction of endogenous antioxidants. ROS are highly reactive molecules produced by oxygen. Examples of ROS include peroxides, super-oxides, and hydroxyl radicals. ROS are produced in cellular responses to xenobiotics and bacterial invasion and during mitochondrial oxidative metabolism. Excessive ROS can trigger oxidative stress that initiates the progression of eye lens opacities. ROS and other free radicals are highly reactive molecules because their outer orbitals have one or more unpaired electrons and can be neutralized by electron-donating compounds, such as antioxidants. Examples of natural antioxidant compounds are vitamin C, vitamin E, and beta-carotene. Numerous studies have demonstrated that plants contain numerous antioxidant compounds that can be used as cataract preventatives or inhibitors. Natural antioxidant extracts for cataract therapy may be investigated further in light of these findings, which show that consuming a sufficient amount of antioxidant-rich plants is an excellent approach to cataract prevention. Several other natural compounds also prevent cataracts by inhibiting aldose reductase and preventing apoptosis of the eye lens.

Galactokinase deficiency: a treatable cause of bilateral cataracts

Congenital cataract can be caused by several systemic diseases and differential diagnosis should be done between infections, genetic or metabolic diseases. We present a case of a 12-month-old girl with bilateral nuclear cataracts that was referred for investigation. Since she did not present a family history of congenital cataracts or metabolic diseases, and her physical examination was normal, a systemic evaluation was performed. Biochemical studies disclosed abnormal galactose metabolism signs. The diagnosis of galactokinase (GALK1) deficiency was considered and the study of the GALK1 gene allowed identifying a pathogenic genetic variant and a predictably pathogenic missense mutation, previously not described. Dietary measures were imposed with a good evolution.

Risk factors associated with congenital defects that alter hearing or vision in children born in the city of Bogotá between 2002 and 2016

INTRODUCTION

Congenital defects affecting the auditory and visual capacity of newborns represent a public health problem as they result in substantial disability, directly impacting the quality of life of newborns and their families.

OBJECTIVE

To evaluate risk factors associated with congenital defects that alter hearing or vision in newborns in the city of Bogotá between 2002 and 2016.

METHOD

Data from the Bogotá Birth Defects Surveillance and Follow-up Program was used, which consolidated data regarding 167 ECLAMC study (Estudio Colaborativo Latino Americano de Malformaciones Congénitas, in spanish) variables in a case-control design to identify risk factors for birth defects after parents provided signed informed consent. Cases were defined as any newborn (alive or stillborn) with a weight greater than 500 g with any visual or hearing abnormality. Controls were defined as newborn in the same hospital and month with no birth defects. Groups were formed according to the case presentation as follows: isolated eye anomaly, isolated ear anomaly, polymalformative, syndromic, and teratogenic.

RESULTS

In total, 402,657 births were reviewed, of which 968 cases had some congenital defects that alter hearing or vision. An association was found between the presence of defects and prematurity, as well as between syndromic cases and increasing maternal age. When comparing cases and controls with the risk of having a birth defect, multiparity had an odds ratio (OR) of 1.47 (95% CI: 1.27-1.71), acute respiratory infection had an OR of 2.41 (95% CI: 1.04-5.58), low maternal education level had an OR of 1.34 (95% CI:1.10-1.62), low paternal education had an OR of 1.42, (95% CI:1.17-1.73), manual labor in the maternal occupation had an OR of 1.31 (95% CI:1.03-1.67), and a history of congenital anomalies in the family had an OR of 1.55 (95% CI:1.19-2.00).

CONCLUSION

This research allowed the identification of epidemiological data and significant risk factors for congenital defects that alter hearing or vision in the population of Bogotá.

Recommendations for newborn screening for galactokinase deficiency: A systematic review and evaluation of Dutch newborn screening data

INTRODUCTION

Galactokinase (GALK) deficiency causes cataract leading to severe developmental consequences unless treated early. Because of the easy prevention and rapid reversibility of cataract with treatment, the Dutch Health Council advised to include GALK deficiency in the Dutch newborn screening program. The aim of this study is to establish the optimal screening method and cut-off value (COV) for GALK deficiency screening by performing a systematic review of the literature of screening strategies and total galactose (TGAL) values and by evaluating TGAL values in the first week of life in a cohort of screened newborns in the Netherlands.

METHODS

Systematic literature search strategies in OVID MEDLINE and OVID EMBASE were developed and study selection, data collection and analyses were performed by two independent investigators. A range of TGAL values measured by the Quantase Neonatal Total Galactose screening assay in a cohort of Dutch newborns in 2007 was evaluated.

RESULTS

Eight publications were included in the systematic review. All four studies describing screening strategies used TGAL as the primary screening marker combined with galactose-1-phosphate uridyltransferase (GALT) measurement that is used for classical galactosemia screening. TGAL COVs of 2200 μmol/L, 1665 μmol/L and 1110 μmol/L blood resulted in positive predictive values (PPV) of 100%, 82% and 10% respectively. TGAL values measured in the newborn period were reported for 39 GALK deficiency patients with individual values ranging from 3963 to 8159 μmol/L blood and 2 group values with mean 8892 μmol/L blood (SD ± 5243) and 4856 μmol/L blood (SD ± 461). Dutch newborn screening data of 72,786 newborns from 2007 provided a median TGAL value of 110 μmol/L blood with a range of 30-2431 μmol/L blood.

CONCLUSION

Based on TGAL values measured in GALK deficiency patients reported in the literature and TGAL measurements in the Dutch cohort by newborn screening we suggest to perform the GALK screening with TGAL as a primary marker with a COV of 2500 μmol/L blood, combined with GALT enzyme activity measurement as used in the classical galactosemia screening, to ensure detection of GALK deficiency patients and minimize false positive referrals.

Pilot study of classic galactosemia: Neurodevelopmental impact and other complications urge neonatal screening in Egypt

Classic galactosemia is caused by deficiency of galactose-1-phosphate uridylyltransferase (GALT). It causes serious morbidity and mortality if left untreated. Screening for galactosemia is not included in Egyptian neonatal screening program. The study aimed to define clinical presentation and complications of galactosemia at Pediatric Hepatology Clinic, Cairo University, Egypt. Thus, the clinical presentation, course and outcome of 37 children with documented galactosemia was studied. Jaundice was the main presentation (67.6%). Other presentations included; convulsions (29.7%), motor retardation (24.3%), mental retardation (5.4%), microcephaly (5.4%), failure to thrive (16.2%), hepatomegaly (62.2%), splenomegaly (35.1%), vomiting (16.2%), diarrhea (8.1%), liver cell failure (10.8%), renal tubular acidosis (5.4%), cataract (5.4%), autoimmune hepatitis (2.7%), self-mutilation (2.7%), combined immune deficiency (2.7%) and kernicterus (2.7%). There was no correlation of residual enzyme activity to severity, clinical presentation, liver function tests, liver biopsy findings or outcome apart from highly significant correlation with repeated chest infections (P = 0.001). Duration to diagnosis and exposure to galactose in diet correlated with liver pathology severity i.e. hepatocyte necrosis (P = 0.003) and cytoskeleton damage (P = 0.003), but not to outcome. Galactosemia should be suspected in any child with liver, neurologic disease and/or immunodeficiency. Its complications are potentially preventable. Early detection is mandatory to prevent serious morbidity and mortality. Initiation of neonatal screening for galactosemia in Egypt is recommended.

Clinical evaluation and mutational analysis of GALK and GALE genes in patients with galactosemia in Greece: one novel mutation and two rare cases

BACKGROUND

Deficiencies of galactokinase (GALK) and UDP-epimerase (GALE) are implicated with galactose metabolic disorders. The aim of the study was the identification of mutations in GALK and GALE genes and clinical evaluation of patients.

METHODS

Five patients with GALK and five with GALE deficiency were picked up via the Neonatal Screening Program. Additionally, two females, 4 years old, were referred with late diagnosed galactosemia, as rare cases. Mutational analysis was conducted via Sanger sequencing, while in silico analysis tools were utilized for the novel mutation. Psychomotor and speech development tests were performed, as well.

RESULTS

The mutation p.Pro28Thr was identified in both alleles in GALK-deficient patients of Roma (gypsy) origin, whereas the novel p.Asn39Ser was detected in two non-Roma patients. In GALE-deficient patients benign and/or likely benign mutations were found. Psychomotor and speech delay were determined in the Roma GALK patients. In each of the late diagnosed females, four mutations were identified in all galactosemia-related genes.

CONCLUSIONS

The mutational spectrums of GALE- and GALK-deficient patients in Greece are presented for the first time along with a clinical evaluation. Mutational analysis in all galactosemia-related genes of symptomatic patients is highly recommended for future cases.

Coordinated movement, neuromuscular synaptogenesis and trans-synaptic signaling defects in Drosophila galactosemia models

The multiple galactosemia disease states manifest long-term neurological symptoms. Galactosemia I results from loss of galactose-1-phosphate uridyltransferase (GALT), which converts galactose-1-phosphate + UDP-glucose to glucose-1-phosphate + UDP-galactose. Galactosemia II results from loss of galactokinase (GALK), phosphorylating galactose to galactose-1-phosphate. Galactosemia III results from the loss of UDP-galactose 4'-epimerase (GALE), which interconverts UDP-galactose and UDP-glucose, as well as UDP-N-acetylgalactosamine and UDP-N-acetylglucosamine. UDP-glucose pyrophosphorylase (UGP) alternatively makes UDP-galactose from uridine triphosphate and galactose-1-phosphate. All four UDP-sugars are essential donors for glycoprotein biosynthesis with critical roles at the developing neuromuscular synapse. Drosophila galactosemia I (dGALT) and II (dGALK) disease models genetically interact; manifesting deficits in coordinated movement, neuromuscular junction (NMJ) development, synaptic glycosylation, and Wnt trans-synaptic signalling. Similarly, dGALE and dUGP mutants display striking locomotor and NMJ formation defects, including expanded synaptic arbours, glycosylation losses, and differential changes in Wnt trans-synaptic signalling. In combination with dGALT loss, both dGALE and dUGP mutants compromise the synaptomatrix glycan environment that regulates Wnt trans-synaptic signalling that drives 1) presynaptic Futsch/MAP1b microtubule dynamics and 2) postsynaptic Frizzled nuclear import (FNI). Taken together, these findings indicate UDP-sugar balance is a key modifier of neurological outcomes in all three interacting galactosemia disease models, suggest that Futsch homolog MAP1B and the Wnt Frizzled receptor may be disease-relevant targets in epimerase and transferase galactosemias, and identify UGP as promising new potential therapeutic target for galactosemia neuropathology.

Newborn screening for galactosemia: a 30-year single center experience

BACKGROUND

Galactosemia due to complete or near-complete galactose-1-phosphate uridyltransferase (GALT) deficiency was the first disorder added to the pioneering newborn screening panel besides phenylketonuria. In the last 50 years, many criticisms have been focused on the opportunity of its inclusion. Consequently, long-term single center experiences with this issue are generally lacking.

METHODS

We reviewed the outcome of newborn screening for hypergalactosemia performed at our department since 1982 and the correspondent long-term clinical outcome.

RESULTS

Among 1 123 909 newborns screened for hypergalactosemia, 33 showed abnormal results confirmed at second tier test. Thirteen patients were affected with classic galactosemia, 8 partial GALT deficiency, 3 severe galactokinase deficiency, 7 transient galactosemia, one congenital porto-systemic shunt, and one glucose transporter 2 deficiency. Acute neonatal liver failure in the late first week of life (5.8±1.1 days) unavoidably complicated the clinical course of classic galactosemia, unless in three second-born siblings treated on the basis of presumptive diagnosis immediately after newborn screening sample collection on day 3. Despite early treatment and long-term steadily normal peripheral blood galactose, 77% of patients with severe GALT deficiency present mild to severe intellectual disabilities. All patients with partial GALT deficiency showed normal intellectual development on a regular diet, as well as patients with galactokinase deficiency under treatment.

CONCLUSIONS

Availability of screening results within the fifth day after birth would allow the prevention of acute decompensation in classic galactosemia. A systematic diagnostic work-up in all positive newborns is essential to unravel the etiology of hypergalactosemia.

Newborn screening for galactosemia in the United States: looking back, looking around, and looking ahead

It has been 50 years since the first newborn screening (NBS) test for galactosemia was conducted in Oregon, and almost 10 years since the last US state added galactosemia to their NBS panel. During that time an estimated >2,500 babies with classic galactosemia have been identified by NBS. Most of these infants were spared the trauma of acute disease by early diagnosis and intervention, and many are alive today because of NBS. Newborn screening for galactosemia is a success story, but not yet a story with a completely happy ending. NBS, follow-up testing, and intervention for galactosemia continue to present challenges that highlight gaps in our knowledge. Here we compare galactosemia screening and follow-up data from 39 NBS programs gathered from the states directly or from public sources. On some matters the programs agreed: for example, those providing relevant data all identify classic galactosemia in close to 1/50,000 newborns and recommend immediate and lifelong dietary restriction of galactose for those infants. On other matters the programs disagree. For example, Duarte galactosemia (DG) detection rates vary dramatically among states, largely reflecting differences in screening approach. For infants diagnosed with DG, >80% of the programs surveyed recommend complete or partial dietary galactose restriction for the first year of life, or give mixed recommendations; <20% recommend no intervention. This disparity presents an ongoing dilemma for families and healthcare providers that could and should be resolved.

Quantification of total hexose on dry blood spot by tandem mass spectrometry

BACKGROUND

Because hypoglycemia and hyperglycemia are harmful and not always associated with overt clinical signs, it is necessary to have methods available to screen for glucose levels to detect hypoglycemia and diabetes as early as possible. A new method for such screening and the clinical determination of blood total hexose on a dry blood spot (DBS) using tandem mass spectrometry (MS/MS) was developed.

METHODS

The serum glucose controls and blood were prepared as DBS and then extracted into a methanol solution containing isotope-labeled internal standards. The methanolic extraction was subjected to HPLC, followed by MS/MS in positive ion mode. Multiple-reaction monitoring of m/z 203.1→23 was used to detect hexose, and m/z 209.0→23 was used for 13C6-D-glucose.

RESULTS

The recoveries of blood glucose by MS/MS were 90%-102% with an R(2) value of 0.999 after linear regression (p<0.001). The controls were within an acceptable range, and the coefficients of variation were less than 10%. The blood total hexose in neonates aged 3-7 days (6.41±1.46 mmol/L) was lower than that in neonates aged 8-30 days (6.66±1.38 mmol/L), and it was lower in neonates than in children aged 1-72 months (7.19±1.87 mmol/L).

CONCLUSION

Quantification of total hexose on a dry blood spot by MS/MS is accurate, reliable and feasible for screening and clinical tests.