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Data de publicació electrònica: 04-04-2022 Pathogenic variants in A Disintegrin And Metalloproteinase (ADAM) 22, the postsynaptic cell membrane receptor for the glycoprotein leucine-rich repeat glioma-inactivated protein 1 (LGI1), have been recently associated with recessive developmental and epileptic encephalopathy. However, so far, only two affected individuals have been described and many features of this disorder are unknown. We refine the phenotype and report 19 additional individuals harboring compound heterozygous or homozygous inactivating ADAM22 variants, of whom 18 had clinical data available. Additionally, we provide follow-up data from two previously reported cases. All affected individuals exhibited infantile-onset, treatment-resistant epilepsy. Additional clinical features included moderate to profound global developmental delay/intellectual disability (20/20), hypotonia (12/20), delayed motor development (19/20). Brain MRI findings included cerebral atrophy (13/20), supported by post-mortem histological examination in patient-derived brain tissue, cerebellar vermis atrophy (5/20), and callosal hypoplasia (4/20). Functional studies in transfected cell lines confirmed the deleteriousness of all identified variants and indicated at least three distinct pathological mechanisms: defective cell membrane expression (1), impaired LGI1-binding (2), and/or impaired interaction with the postsynaptic density protein PSD-95 (3). We reveal novel clinical and molecular hallmarks of ADAM22 deficiency and provide knowledge that might inform clinical management and early diagnostics. Funding: most families were collected as part of the SYNaPS Study Group collaboration funded by the Wellcome Trust and strategic award (Synaptopathies) funding (WT093205 MA and WT104033AIA). This study was also supported by JSPS/MEXT KAKENHI (Grants 19H03331, 19K22439 and 21K19390 to Y.F., Grant 19K16269 to Y.M., and Grants 20H00459 and 20H04915 to M.F.) and Japan Agency for Medical Research and Development (21wm0525022h0001 to Y.F.); intramural funding (fortüne) from the University of Tübingen (Grant 2545-1-0) and the Ministry of Science, Research and Art Baden-Württemberg to B.V. P.S. contributed to this work within the framework of the DINOGMI Department of Excellence of MIUR 2018-2022 (legge 232 del 2016). T.B.H. was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 418081722, 433158657. I.S.P., V.Y.V. are supported by the Government Assignment of the Russian Ministry of Health (#121061500066-2). HL receives support from the Canadian Institutes of Health Research (Foundation Grant FDN-167281), the Canadian Institutes of Health Research and Muscular Dystrophy Canada (Network Catalyst Grant for NMD4C), the Canada Foundation for Innovation (CFI-JELF 38412), and the Canada Research Chairs program (Canada Research Chair in Neuromuscular Genomics and Health, 950-232279). S.H. is funded by TUBITAK (Turkish Scientific and Technological Research Council) Project number 216S771. R.H. is a Wellcome Trust Investigator (109915/Z/15/Z), who received support from the Medical Research Council (UK) (MR/N025431/1 and MR/V009346/1), the European Research Council (309548), the Newton Fund (UK/Turkey, MR/N027302/1), the Addenbrookes Charitable Trust (G100142), the Evelyn Trust, the Stoneygate Trust, the Lily Foundation and an MRC strategic award to establish an International Centre for Genomic Medicine in Neuromuscular Diseases (ICGNMD) MR/S005021/1. This research was supported by the NIHR Cambridge Biomedical Research Centre (BRC-1215-20014)

Schmid metaphyseal chondrodysplasia is a rare genetic cause of skeletal dysplasia. Patients usually present skeletal abnormalities but no major visceral malformations or intellectual disability. We report a case of a 2-year-old male patient with short stature, progressive genu varum, and waddling gait. Radiographic findings were essential to guide investigation and molecular confirmation, allowing proper treatment and genetic counseling.

The cytochrome c-oxidase (COX) enzyme, also known as mitochondrial complex IV (MT-C4D), is a transmembrane protein complex found in mitochondria. COX deficiency is one of the most frequent causes of electron transport chain defects in humans. Therefore, high energy demand organs and tissues are affected in patients with mutations in the COX15 gene, with variable phenotypic expressiveness. We describe the case of a male newborn with hypertrophic cardiomyopathy and serum and cerebrospinal fluid hyperlacticaemia, whose exome sequencing revealed two variants in a compound heterozygous state: c.232G > A; p.(Gly78Arg), classified as likely pathogenic, and c.452C > G; p.(Ser151Ter), as pathogenic; the former never previously described in the literature.

Leigh syndrome is an early onset progressive disorder caused by defects in mitochondrial oxidative phosphorylation. Pathogenic variants in nuclear and mitochondrial genes are associated with the syndrome. Homozygous pathogenic variants in the C12orf65 gene impair the mitochondrial oxidative phosphorylation system. We describe a new case of Leigh syndrome caused by a novel pathogenic variant of the C12orf65 gene resulting in the lack of the Gly-Gly-Gln (GGQ) domain in the predicted protein, and review clinical and molecular data from previously reported patients. Our study supports that the phenotype caused by C12orf65 gene variants is heterogeneous and varies from spastic paraparesis to Leigh syndrome. Loss-of-function variants are more likely to cause the disease, and variants affecting the GGQ domain tend to be associated with more severe phenotypes, reinforcing a possible genotype-phenotype correlation.