Neuropsychological stability in classical galactosemia: A pilot study in 10 adult patients.

Classical galactosemia (CG) is an autosomal recessive disorder of galactose metabolism. Despite early initiation of a galactose-restricted diet, patients develop long-term complications including cognitive impairment. There is an ongoing debate whether the cognitive impairment in CG is stable throughout life or progresses with age. Earlier cross-sectional and longitudinal studies regarding intelligence suggest stability, but longitudinal neuropsychological studies focusing on specific cognitive functions are limited. Therefore, the aim of this study is to assess cognitive change over time in adult CG-patients. Ten adult patients with normal to borderline intelligence (mean age 33 years, range 22-49; IQ≥70 or independent work- or living situation) were assessed twice with a mean time interval of 3 years and 9 months (range 1023-1575 days). The neuropsychological assessments covered information processing speed, executive functioning, verbal fluency, and visuospatial functioning. Results showed that there was no significant decline or improvement in test scores on all neuropsychological measures except a decline on the Trail Making Test-A (p = 0.048). However, this group-level difference was subject to "regression to the mean" and was not endorsed by significant change in test scores measuring the same cognitive domain. Moreover, no specific pattern of reliable change (RCI > -1.96) was present on specific measures or within individual patients. This explorative study performed in 10 adult CG-patients with normal to borderline intelligence revealed no cognitive change on several cognitive domains. This implies that the subset of adults with a normal to borderline IQ in their early and middle adulthood are cognitively stable.

Social cognition, emotion regulation and social competence in classical galactosemia patients without intellectual disability.

OBJECTIVE: Classical galactosemia (CG) is an inborn error of galactose metabolism. Many CG patients suffer from long-term complications including poor cognitive functioning. There are indications of social dysfunction but limited evidence in the literature. Therefore, this study aims to improve our understanding of social competence in CG by investigating social cognition, neurocognition and emotion regulation. METHODS: A comprehensive (neuro)psychological test battery, including self and proxy questionnaires, was administered to CG patients without intellectual disability. Social cognition was assessed by facial emotion recognition, Theory of Mind and self-reported empathy. Standardised results were compared to normative data of the general population. RESULTS: Data from 23 patients (aged 8-52) were included in the study. On a group level, CG patients reported satisfaction with social roles and no social dysfunction despite the self-report of lower social skills. They showed deficits in all aspects of social cognition on both performance tests (emotion recognition and Theory of Mind) and self-report questionnaires (empathy). Adults had a lower social participation than the general population. Parents reported lower social functioning, less adaptive emotion regulation and communication difficulties in their children. Individual differences in scores were present. CONCLUSION: This study shows that CG patients without intellectual disability are satisfied with their social competence, especially social functioning. Nevertheless, deficits in social cognition are present in a large proportion of CG patients. Due to the large variability in scores and discrepancies between self- and proxy-report, an individually tailored, comprehensive neuropsychological assessment including social cognition is advised in all CG patients. Treatment plans need to be customised to the individual patient.

The challenges of classical galactosemia: HRQoL in pediatric and adult patients.

BACKGROUND: Classical galactosemia (CG), an inborn error of galactose metabolism, results in long-term complications including cognitive impairment and movement disorders, despite early diagnosis and dietary treatment. Two decades ago, lower motor-, cognitive- and social health related quality of life (HRQoL) was demonstrated in pediatric and adult patients. Since then, the diet has been relaxed, newborn screening was implemented and new international guidelines resulted in major changes in follow-up. The aim of this study was to assess HRQoL of CG by means of online self- and/or proxy-HRQoL-questionnaires focusing on the main areas of concern of CG (i.e. anxiety, depression, cognition, fatigue, social- and upper extremity function) within the patient-reported outcomes measurement information system (PROMIS®) and generic HRQoL-questionnaires (TAPQOL, TACQOL, TAAQOL). RESULTS: Data of 61 Dutch patients (aged 1-52 years) were collected and compared to available Dutch or US reference populations. On the PROMIS-questionnaires, children reported more fatigue (P = 0.044), lower function in upper extremities (P = 0.021), more cognitive difficulties (P = 0.055, d = 0.56) and higher anxiety (P = 0.063, d = 0.52) than reference children although the latter findings remained non-significant. Parents of CG patients reported lower quality of peer relationships of their children (P < 0.001). Both children and parents reported lower cognitive functioning (P = 0.005, P = 0.010) on the TACQOL. Adults reported on PROMIS domains lower cognitive functioning (P = 0.030), higher anxiety (P = 0.004) and more fatigue (P = 0.026). Cognitive difficulties were reported on the TAAQOL by adults (P < 0.001), as well as physical-, sleeping and social difficulties. CONCLUSIONS: CG remains to impact the HRQoL of pediatric and adult patients negatively on several domains including cognition, anxiety, motor function and fatigue. A lower social health was mainly reported by parents, and not by patients themselves. The Covid-19 pandemic might have amplified the results on anxiety although higher levels of anxiety fit pre-pandemic findings. The reported fatigue is a new finding in CG. Because the effect of lockdown fatigue could not be eliminated and fatigue is a frequent finding in patients with chronic disorders, future studies are warranted. Clinicians and researchers should be attentive to both pediatric and adult patients, and the age-dependent difficulties they might encounter.

Multi-omics in classical galactosemia: Evidence for the involvement of multiple metabolic pathways.

Classical galactosemia (CG) is one of the more frequent inborn errors of metabolism affecting approximately 1:40.000 people. Despite a life-saving galactose-restricted diet, patients develop highly variable long-term complications including intellectual disability and movement disorders. The pathophysiology of these complications is still poorly understood and development of new therapies is hampered by a lack of valid prognostic biomarkers. Multi-omics approaches may discover new biomarkers and improve prediction of patient outcome. In the current study, (semi-)targeted mass-spectrometry based metabolomics and lipidomics were performed in erythrocytes of 40 patients with both classical and variant phenotypes and 39 controls. Lipidomics did not show any significant changes or deficiencies. The metabolomics analysis revealed that CG does not only compromise the Leloir pathway, but also involves other metabolic pathways including glycolysis, the pentose phosphate pathway, and nucleotide metabolism in the erythrocyte. Moreover, the energy status of the cell appears to be compromised, with significantly decreased levels of ATP and ADP. This possibly is the consequence of two different mechanisms: impaired formation of ATP from ADP possibly due to reduced flux though the glycolytic pathway and trapping of phosphate in galactose-1-phosphate (Gal-1P) which accumulates in CG. Our findings are in line with the current notion that the accumulation of Gal-1P plays a key role in the pathophysiology of CG not only by depletion of intracellular phosphate levels but also by decreasing metabolite abundance downstream in the glycolytic pathway and affecting other pathways. New therapeutic options for CG could be directed towards the restoration of intracellular phosphate homeostasis.

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.

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.