Exploring the Prevalence of Duplication and Deletion in Russia and Its Impact on Carrier Screening.

5q spinal muscular atrophy (5q SMA) is one of the most prevalent autosomal recessive disorders worldwide. In 5q SMA, cases of silent carriers have been reported, including duplications, intragenic subtle variants, de novo variants, and mosaicism. This study included DNA samples from 3412 unexamined unrelated individuals with no known family history of 5q SMA. In addition, we studied 15 families in which the children had a confirmed diagnosis of 5q SMA caused by a homozygous deletion of exon 7 of . Each family included one parent who was a carrier of a heterozygous deletion of , while the other parent had two copies of . The copy number of and was detected by MLPA. Two previously reported genetic markers of duplication, c.*3+80T>G and c.*211_*212del, were tested in 143 Russian residents with three copies of and 15 parents with two copies of . The frequency of a heterozygous carrier of exon 7 deletion of is 1 in 36 individuals (95% CI 33 to 39). The frequency of exon 7 duplication of is 1 in 25 individuals (95% CI 20 to 30). Only three individuals of the studied duplication carriers were detected to have genetic markers of duplication. The study of duplication genetic markers (c.*3+80T>G and c.*211_*212del) in Russian residents reveals only 1.9% of duplication carriers.