The continuously evolving phenotype of succinic semialdehyde dehydrogenase deficiency.

The objective of the study is to evaluate the evolving phenotype and genetic spectrum of patients with succinic semialdehyde dehydrogenase deficiency (SSADHD) in long-term follow-up. Longitudinal clinical and biochemical data of 22 pediatric and 9 adult individuals with SSADHD from the patient registry of the International Working Group on Neurotransmitter related Disorders (iNTD) were studied with in silico analyses, pathogenicity scores and molecular modeling of ALDH5A1 variants. Leading initial symptoms, with onset in infancy, were developmental delay and hypotonia. Year of birth and specific initial symptoms influenced the diagnostic delay. Clinical phenotype of 26 individuals (median 12 years, range 1.8-33.4 years) showed a diversifying course in follow-up: 77% behavioral problems, 76% coordination problems, 73% speech disorders, 58% epileptic seizures and 40% movement disorders. After ataxia, dystonia (19%), chorea (11%) and hypokinesia (15%) were the most frequent movement disorders. Involvement of the dentate nucleus in brain imaging was observed together with movement disorders or coordination problems. Short attention span (78.6%) and distractibility (71.4%) were the most frequently behavior traits mentioned by parents while impulsiveness, problems communicating wishes or needs and compulsive behavior were addressed as strongly interfering with family life. Treatment was mainly aimed to control epileptic seizures and psychiatric symptoms. Four new pathogenic variants were identified. In silico scoring system, protein activity and pathogenicity score revealed a high correlation. A genotype/phenotype correlation was not observed, even in siblings. This study presents the diversifying characteristics of disease phenotype during the disease course, highlighting movement disorders, widens the knowledge on the genotypic spectrum of SSADHD and emphasizes a reliable application of in silico approaches.

Expanding the phenotypic spectrum of TRAPPC11-related muscular dystrophy: 25 Roma individuals carrying a founder variant.

BACKGROUND: Limb-girdle muscular dystrophies (LGMD) are a heterogeneous group of genetically determined muscle disorders. TRAPPC11-related LGMD is an autosomal-recessive condition characterised by muscle weakness and intellectual disability. METHODS: A clinical and histopathological characterisation of 25 Roma individuals with LGMD R18 caused by the homozygous TRAPPC11 c.1287+5G>A variant is reported. Functional effects of the variant on mitochondrial function were investigated. RESULTS: The c.1287+5G>A variant leads to a phenotype characterised by early onset muscle weakness, movement disorder, intellectual disability and elevated serum creatine kinase, which is similar to other series. As novel clinical findings, we found that microcephaly is almost universal and that infections in the first years of life seem to act as triggers for a psychomotor regression and onset of seizures in several individuals with TRAPPC11 variants, who showed pseudometabolic crises triggered by infections. Our functional studies expanded the role of TRAPPC11 deficiency in mitochondrial function, as a decreased mitochondrial ATP production capacity and alterations in the mitochondrial network architecture were detected. CONCLUSION: We provide a comprehensive phenotypic characterisation of the pathogenic variant TRAPPC11 c.1287+5G>A, which is founder in the Roma population. Our observations indicate that some typical features of golgipathies, such as microcephaly and clinical decompensation associated with infections, are prevalent in individuals with LGMD R18.

Integrative Approach to Predict Severity in Nonketotic Hyperglycinemia.

OBJECTIVE: Glycine encephalopathy, also known as nonketotic hyperglycinemia (NKH), is an inherited neurometabolic disorder with variable clinical course and severity, ranging from infantile epileptic encephalopathy to psychiatric disorders. A precise phenotypic characterization and an evaluation of predictive approaches are needed. METHODS: Longitudinal clinical and biochemical data of 25 individuals with NKH from the patient registry of the International Working Group on Neurotransmitter Related Disorders were studied with in silico analyses, pathogenicity scores, and molecular modeling of GLDC and AMT variants. RESULTS: Symptom onset (p < 0.01) and diagnosis occur earlier in life in severe NKH (p < 0.01). Presenting symptoms affect the age at diagnosis. Psychiatric problems occur predominantly in attenuated NKH. Onset age ≥ 3 months (66% specificity, 100% sensitivity, area under the curve [AUC] = 0.87) and cerebrospinal fluid (CSF)/plasma glycine ratio ≤ 0.09 (57% specificity, 100% sensitivity, AUC = 0.88) are sensitive indicators for attenuated NKH, whereas CSF glycine concentration ≥ 116.5µmol/l (100% specificity, 93% sensitivity, AUC = 0.97) and CSF/plasma glycine ratio ≥ 0.15 (100% specificity, 64% sensitivity, AUC = 0.88) are specific for severe forms. A ratio threshold of 0.128 discriminates the overlapping range. We present 10 new GLDC variants. Two mild variants resulted in attenuated, whereas 2 severe variants or 1 mild and 1 severe variant led to severe phenotype. Based on clinical, biochemical, and genetic parameters, we propose a severity prediction model. INTERPRETATION: This study widens the phenotypic spectrum of attenuated NKH and expands the number of pathogenic variants. The multiparametric approach provides a promising tool to predict disease severity, helping to improve clinical management strategies. ANN NEUROL 2022;92:292-303.

Assessment of intellectual impairment, health-related quality of life, and behavioral phenotype in patients with neurotransmitter related disorders: Data from the iNTD registry.

Inherited disorders of neurotransmitter metabolism are a group of rare diseases, which are caused by impaired synthesis, transport, or degradation of neurotransmitters or cofactors and result in various degrees of delayed or impaired psychomotor development. To assess the effect of neurotransmitter deficiencies on intelligence, quality of life, and behavior, the data of 148 patients in the registry of the International Working Group on Neurotransmitter Related Disorders (iNTD) was evaluated using results from standardized age-adjusted tests and questionnaires. Patients with a primary disorder of monoamine metabolism had lower IQ scores (mean IQ 58, range 40-100) within the range of cognitive impairment (<70) compared to patients with a BH4 deficiency (mean IQ 84, range 40-129). Short attention span and distractibility were most frequently mentioned by parents, while patients reported most frequently anxiety and distractibility when asked for behavioral traits. In individuals with succinic semialdehyde dehydrogenase deficiency, self-stimulatory behaviors were commonly reported by parents, whereas in patients with dopamine transporter deficiency, DNAJC12 deficiency, and monoamine oxidase A deficiency, self-injurious or mutilating behaviors have commonly been observed. Phobic fears were increased in patients with 6-pyruvoyltetrahydropterin synthase deficiency, while individuals with sepiapterin reductase deficiency frequently experienced communication and sleep difficulties. Patients with BH4 deficiencies achieved significantly higher quality of life as compared to other groups. This analysis of the iNTD registry data highlights: (a) difference in IQ and subdomains of quality of life between BH4 deficiencies and primary neurotransmitter-related disorders and (b) previously underreported behavioral traits.