Recessive NUP54 Variants Underlie Early-Onset Dystonia with Striatal Lesions

Infantile striatonigral degeneration is caused by a homozygous variant of the nuclear-pore complex (NPC) gene NUP62, involved in nucleo-cytoplasmic trafficking. By querying sequencing-datasets of patients with dystonia and/or Leigh(-like) syndromes, we identified 3 unrelated individuals with biallelic variants in NUP54. All variants clustered in the C-terminal protein region that interacts with NUP62. Associated phenotypes were similar to those of NUP62-related disease, including early-onset dystonia with dysphagia, choreoathetosis, and T2-hyperintense lesions in striatum. In silico and protein-biochemical studies gave further evidence for the argument that the variants were pathogenic. We expand the spectrum of NPC component-associated dystonic conditions with localized basal-ganglia abnormalities. ANN NEUROL 2023;93:330-335.

UQCRC2-related mitochondrial complex III deficiency, about 7 patients

Isolated complex III defect is a relatively rare cause of mitochondrial disorder. New genes involved were identified in the last two decades, with only a few cases described for each deficiency. UQCRC2, which encodes ubiquinol-cytochrome c reductase core protein 2, is one of the eleven structural subunits of complex III. We report seven French patients with UQCRC2 deficiency to complete the phenotype reported so far. We highlight the similarities with neoglucogenesis defect during decompensations - hypoglycaemias, liver failure and lactic acidosis - and point out the rapid improvement with glucose fluid infusion, which is a remarkable feature for a mitochondrial disorder. Finally, we discuss the relevance of coenzyme Q10 supplementation in this defect.

Sebelipase alfa enzyme replacement therapy in Wolman disease: a nationwide cohort with up to ten years of follow-up

BACKGROUND

Wolman disease (WD), the rapidly progressive phenotype of lysosomal acid lipase (LAL) deficiency, presents in neonates with failure to thrive and hepatosplenomegaly, and leads to multi-organ failure and death before 12 months of age. In clinical trials, enzyme replacement therapy (ERT) with sebelipase alfa led to improved survival, growth and biological parameters in WD patients followed up to 5 years. Long-term follow-up and health-related quality of life (HRQoL) evaluation are lacking.

RESULTS

We performed a nationwide, retrospective study of sebelipase alfa in WD patients. Five patients with abolished LAL activity and bi-allelic LIPA mutations were included with a median follow-up of 7 years (1-10). ERT was initiated at a median age of 1 month (0-4). Infusion tolerance was excellent on the long-term with only one patient requiring systematic pre-medication. Cholestyramine, fat-soluble vitamin supplements and a specific diet (high in medium-chain triglycerides and low in long-chain fatty acids) were prescribed. Liver function tests, plasma lipid profiles, fat-soluble vitamin levels and growth parameters improved. Three patients transiently exhibited a neuromyopathic phenotype (footdrop gait, waddling walk or muscle fatigue) but electromyography and muscle strength testing were normal. At last follow-up, all patients were alive with normal growth parameters and a satisfactory HRQoL, no patient had special education needs, and one patient required parenteral nutrition since an acute gastroenteritis.

CONCLUSIONS

Early ERT initiation allowed 100% survival with positive outcomes. Very long-term follow-up and hematopoietic stem cell transplantation while on ERT should be evaluated to strengthen the benefits of sebelipase alfa.

Large-scale screening of lipase acid deficiency in at risk population

BACKGROUND

Lysosomal acid lipase deficiency (LALD, OMIM#278000) is a rare lysosomal disorder with an autosomal recessive inheritance. The main clinical manifestations are related to a progressive accumulation of cholesteryl esters, triglycerides or both within the lysosome in different organs such as the liver, spleen, and cardiovascular system. A wide range of clinical severity is associated with LALD including a severe very rare antenatal/neonatal/infantile phenotype named Wolman disease and a late-onset form named cholesteryl ester storage disease (CESD).

METHODS

This study aimed to investigate a cohort of at-risk patients (4174) presenting with clinical or biological signs consistent with LALD using the assessment of LAL activity on dried blood spots.

RESULTS

LAL activity was lower than 0.05 nmol/punch/L (cut-off: 0.12) in 19 patients including 13 CESD and 6 Wolman. Molecular study has been conducted in 17 patients and succeeded in identifying 34 mutated alleles. Fourteen unique variants have been characterized, 7 of which are novel.

CONCLUSION

This study allowed to identify a series of patients and expanded the molecular spectrum knowledge of LALD. Besides, a new screening criteria grid based on the clinical/biological data from our study and the literature has been proposed in order to enhance the diagnosis rate in at risk populations.

Real-life use of videos in pediatric epilepsy consultations

Paroxysmal events are usually not directly observed by physicians. The diagnosis remains challenging and relies mostly on the description of witnesses. The effectiveness of videos for seizure diagnosis has been validated by several studies, but their place in clinical practice is not yet clear. The aim of our study was to evaluate the real-life use of videos by child neurologists. We conducted a three-month prospective study in which child neurologists were asked to use a short questionnaire to evaluate all videos that were watched in their clinical practice for an initial diagnosis or during follow-up. A click-off meeting during the French pediatric neurology meeting allowed to recruit participants. A total of 165 questionnaires were completed by 15 physicians over the study period. The physicians were child neurologists working in secondary and tertiary/university hospitals, consulting children with epilepsy. Based on the evaluation of child neurologists, 51% of the videos consisted of epileptic seizures; 40%, nonepileptic paroxysmal events; and 9%, psychogenic nonepileptic seizures. Most of the videos were made on parental initiative. The use of video has modified the first diagnosis hypothesis in 35% of cases. The physicians' feelings regarding the interest of the video used during the diagnostic phase were similar to those of the video used during follow-up. It appears that videos have become a part of the epilepsy clinic and are helpful for diagnosis as well as during follow-up. Unfortunately, one of the limitations of this study is the absence of private practitioner.

Neurocognitive profiles in MSUD school-age patients

Maple syrup urine disease (MSUD), an inborn error of amino acids catabolism is characterized by accumulation of branched chain amino acids (BCAAs) leucine, isoleucine, valine and their corresponding alpha-ketoacids. Impact on the cognitive development has been reported historically, with developmental delays of varying degree. Currently, earlier diagnosis and improved management allow a better neurodevelopment, without requirement of special education. However, specific impairments can be observed, and so far, results of detailed neurocognitive assessments are not available. The aim of this study was to analyse neurocognitive profiles of French MSUD patients. This was a multicentre retrospective study on MSUD patients who underwent neurocognitive evaluation at primary school age. Twenty-one patients with classical neonatal onset MSUD were included. The patients' mean age at the time of evaluation was 8.7 years. The mean intellectual quotient (IQ) score was in the normal range (95.1 ± 12.6). In a subset of eight patients, a consistent developmental pattern of higher verbal than performance IQ was observed (mean of the difference 25.7 ± 8.7, p < 0.0001). No correlation could be established between this pattern and long-term metabolic balance (BCAA blood levels), or severity of acute metabolic imbalances, or leucine blood levels at diagnosis and time to toxin removal procedure. These data show that some MSUD patients may exhibit an abnormal neurocognitive profile with higher verbal than performance abilities. This might suggest an executive dysfunction disorder that would need to be further investigated by specialized testing. This pattern is important to detect in MSUD, as appropriate neuropsychological treatment strategies should be proposed.

Mutations in MDH2, Encoding a Krebs Cycle Enzyme, Cause Early-Onset Severe Encephalopathy

MDH2 encodes mitochondrial malate dehydrogenase (MDH), which is essential for the conversion of malate to oxaloacetate as part of the proper functioning of the Krebs cycle. We report bi-allelic pathogenic mutations in MDH2 in three unrelated subjects presenting with early-onset generalized hypotonia, psychomotor delay, refractory epilepsy, and elevated lactate in the blood and cerebrospinal fluid. Functional studies in fibroblasts from affected subjects showed both an apparently complete loss of MDH2 levels and MDH2 enzymatic activity close to null. Metabolomics analyses demonstrated a significant concomitant accumulation of the MDH substrate, malate, and fumarate, its immediate precursor in the Krebs cycle, in affected subjects’ fibroblasts. Lentiviral complementation with wild-type MDH2 cDNA restored MDH2 levels and mitochondrial MDH activity. Additionally, introduction of the three missense mutations from the affected subjects into Saccharomyces cerevisiae provided functional evidence to support their pathogenicity. Disruption of the Krebs cycle is a hallmark of cancer, and MDH2 has been recently identified as a novel pheochromocytoma and paraganglioma susceptibility gene. We show that loss-of-function mutations in MDH2 are also associated with severe neurological clinical presentations in children.