Genetic spectrum of sarcoglycanopathies in a cohort of Russian patients

Sarcoglycanopathies encompass four distinct forms of limb-girdle muscular dystrophies (LGMD), denoted as LGMD R3-R6, arising from mutations within the SGCA, SGCB, SGCG, and SGCD genes. The global prevalence of sarcoglycanopathies is low, making it challenging to study these diseases. The principal objective of this study was to explore the spectrum of mutations in a cohort of Russian patients with sarcoglycanopathies and to ascertain the frequency of these conditions in the Russian Federation. We conducted a retrospective analysis of clinical and molecular genetic data from 49 Russian patients with sarcoglycan genes variants. The results indicated that variants in the SGCA gene were found in 71.4% of cases, with SGCB and SGCG genes each exhibiting variants in 12.2 % of patients. SGCD gene variants were detected in 4.1% of cases. Bi-allelic pathogenic and likely pathogenic variants were identified in 46 of the 49 cases of sarcoglycanopathies: LGMD R3 (n = 34), LGMD R4 (n = 4), LGMD R5 (n = 6), and LGMD R6 (n = 2). A total of 31 distinct variants were identified, comprising 25 previously reported and 6 novel variants. Two major variants, c.229C>T and c.271G>A, were detected within the SGCA, constituting 61.4% of all mutant alleles in Russian patients with LGMD R3. Both LGMD R6 cases were caused by the homozygous nonsense variant c.493C>T p.(Arg165Ter) in the SGCD gene. The incidence of sarcoglycanopathies in the Russian Federation was estimated to be at least 1 in 4,115,039, which is lower than the reported incidence in other populations.