Genotype Structure Alterations in 5q SMA Patients as a Result of the Newborn Screening Program Implementation in the Russian Federation.

Since 2023, the Russian Federation (RF) has implemented an expanded newborn screening (NBS) program for 36 hereditary disorders, which now includes 5q spinal muscular atrophy (5q SMA). As a result of newborn screening for 5q SMA conducted in the RF during 2023-2024, 288 newborns with a homozygous deletion of exon 7 in the SMN1 gene were identified by molecular genetic methods. The overall observed incidence of 5q SMA was 1 in 8439 newborns, which does not significantly differ from the expected incidence of 1 in 7953 newborns, established by previous pilot screening projects (p > 0.05). A comparison of the genotypes of patients identified through selective and newborn screening showed statistically significant differences in the proportions of patients carrying two, three, and four or more copies of the SMN2 gene. These findings demonstrate that the NBS program is effective in detecting both individuals with more severe phenotypes, as expected, and those with milder forms of the disease.