The utilization of multiplex PCR with fragment analysis for carrier screening of spinal muscular atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disorder caused by a homozygous deletion of exon 7 in the SMN1 gene, leading to muscle weakness and atrophy. Individuals who are heterozygous for a SMN1 deletion on one chromosome are typically asymptomatic but may pass the mutation to their children. As a result, the American College of Obstetricians and Gynecologists (ACOG) recommends that all women, especially those planning to become pregnant, undergo carrier screening for genetic disorders, including spinal muscular atrophy (SMA), fragile X syndrome (FXS), cystic fibrosis, and sickle cell anemia. In this study, we screened 124 leftover specimens from women of reproductive age (18-45 years) that were previously collected for FMR1 CGG repeat expansion analysis to determine SMA carrier status using multiplex PCR with fragment analysis. We identified 5 individuals as SMA carriers, confirmed by MLPA analysis (5/124, 4.03%). Among these, one individual was classified as a high-risk silent carrier (1 out of 124, or 0.81%). The overall prevalence estimates were 1 in 25 (4.03%) for SMA carriers, 1 in 31 (3.23%) for FMR1 premutation carriers (with 55-200 CGG repeats), and 1 in 124 (0.81%) for individuals with both conditions. In conclusion, the CarrierMax™ SMN1/SMN2 reagent kit demonstrated reliable performance in this study population. It showed that concordance was observed between MLPA and MLPA-based SMA carrier classification for SMN1 copy number determination in spinal muscular atrophy (SMA) carrier screening. These findings also highlight the potential for multiple reproductive genetic risks to coexist within a single individual and emphasize the clinical importance of expanded carrier screening (ECS) approaches.