Expanding the disease phenotype of ADSSL1-associated myopathy in non-Korean patients.

Adenylosuccinate synthase (ADSSL1) is a muscle specific enzyme involved in the purine nucleotide cycle and responsible for the conversion of inosine monophosphate to adenosine monophosphate. Since 2016, when mutations in the ADSSL1 gene were first described to be associated with an adult onset distal myopathy, nine patients with compound heterozygous variants in the ADSSL1 gene, all of Korean origin, have been identified. Here we report a novel ADSSL1 mutation and describe two sporadic cases of Turkish and Indian origin. Many of the clinical features of both patients and muscle histopathology and muscle MRI findings, were in accordance with previously reported findings in the adult onset distal myopathy individuals. However, one of our patients presented with progressive, proximally pronounced weakness, severe muscle atrophy and early contractures. Thus, mutations in ADSSL1 have to be considered in patients with both distal and proximal muscle weakness and across various ethnicities.