Two Lithuanian Cases of Classical Galactosemia with a Literature Review: A Novel GALT Gene Mutation Identified

Galactosemia is a rare autosomal recessive genetic disorder that causes impaired metabolism of the carbohydrate galactose. This leads to severe liver and kidney insufficiency, central nervous system damage and long-term complications in newborns. We present two clinical cases of classical galactosemia diagnosed at the Lithuanian University of Health Sciences (LUHS) Kaunas Clinics hospital and we compare these cases in terms of clinical symptoms and genetic variation in the GALT gene. The main clinical symptoms were jaundice and hepatomegaly, significant weight loss, and lethargy. The clinical presentation of the disease in Patient 1 was more severe than that in Patient 2 due to liver failure and E. coli-induced sepsis. A novel, likely pathogenic GALT variant NM_000155.4:c.305T>C (p.Leu102Pro) was identified and we believe it could be responsible for a more severe course of the disease, although further study is needed to confirm this. It is very important to suspect and diagnose galactosemia as early in its course as possible, and introduce lactose-free formula into the patient’s diet. Wide-scale newborn screening and genetic testing are particularly crucial for the early detection of the disease.

Correction to: Classical galactosemia: neuropsychological and psychosocial functioning beyond intellectual abilities

An amendment to this paper has been published and can be accessed via the original article.

Classical galactosemia: neuropsychological and psychosocial functioning beyond intellectual abilities

Background Despite early diagnosis and treatment, Classical Galactosemia (CG) patients frequently develop long-term complications, such as cognitive impairment. Available literature primarily reports on general intellectual abilities and shows a substantially lower Full Scale Intelligence Quotient (FSIQ) in CG patients than in the general population. Both problems in social functioning as well as internalizing problems are often reported in CG patients. The combination of intelligence, cognitive functioning, behavior and social functioning has not been studied systematically in CG patients. Methods To determine if CG patients demonstrate a specific neuropsychological and psychosocial profile, we investigated intelligence, functioning on multiple cognitive domains, behavior and social functioning with a comprehensive neuropsychological test battery and questionnaires (self- and proxy-reported). Results The data of 48 patients, aged 4–47 years are reported. FSIQ ranged from 45 to 103 (mean 77 ± 14). A negative correlation between age and FSIQ was demonstrated (p = 0.037) which resulted directly from the inclusion of four young ‘milder’ patients detected by newborn screening (NBS) with an expected better clinical outcome. Compared to normative data, patients had significantly lower but highly variable scores on all cognitive domains, especially on tests requiring mental speed. In the context of the FSIQ, 43% of the cognitive test results exceeded IQ based expectations. Overall, the patients’ scores on social functioning were in the normal range but internalizing problems were frequently reported. In our cohort, an early initiation of dietary treatment due to NBS or family screening did not result in a more favorable neuropsychological outcome. Conclusions In this study, we demonstrated that as a cohort, CG patients have a below average intelligence and impaired cognitive functioning without a distinctive neuropsychological profile. The effect of age on neurocognitive functioning should be assessed in longitudinal studies. Social functioning was not impaired, but patients may be at risk for internalizing problems. Considering the large variability in cognitive, behavioral and social functioning and the finding that cognitive outcomes may exceed IQ based expectations, an individual evaluation and follow-up is warranted in all CG patients to ensure timely support if needed.

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.

Cognitive functioning in patients with classical galactosemia: a systematic review

Background Patients with the metabolic disorder classical galactosemia suffer from long-term complications despite a galactose-restricted diet, including a below average intelligence level. The aim of the current review was to investigate the incidence and profile of cognitive impairments in patients with classical galactosemia. Method MEDLINE, EMBASE and PsychINFO were searched up to 23 October 2018 for studies examining information processing speed, attention, memory, language, visuospatial functioning, executive functioning and social cognition in patients with confirmed classical galactosemia utilizing standardized neuropsychological tests. Data synthesis followed a narrative approach, since the planned meta-analysis was not possible due to large variability between the neuropsychological assessments. Results Eleven studies were included, including case-studies. The quality of most studies was moderate to low. As a group, patients with classical galactosemia exhibit below average to low scores on all cognitive domains. A large proportion of the patients perform on an impaired level on attention, memory and vocabulary. Evidence for impairments in information processing speed, language, visuospatial functioning and aspects of executive functioning was limited due to the small number of studies investigating these cognitive functions. Social cognition was not examined at all. Conclusions Given the moderate to low quality of the included studies and the limited evidence in many cognitive domains, the incidence of cognitive impairment in patients with classical galactosemia is not yet clear. Both clinicians and researchers encountering patients with classical galactosemia need to be aware of possible cognitive impairments. Future well-designed studies are needed to determine the cognitive profile of classical galactosemia. This can be the basis for the development of intervention strategies.

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

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