[Newborn screening and early disease-modifying therapy for spinal muscular atrophy in the Foshan region]

Objective: To investigate the genetic epidemiological characteristics of spinal muscular atrophy (SMA) among newborns in Foshan, and to evaluate the efficacy and clinical value of early disease-modifying therapy for affected infants. Methods: A retrospective cohort study was conducted on 132 850 newborns and 5 confinned SMA patients who underwent SMA genetic screening at the Department of Foshan Newborn Disease Screening Center, Foshan Women and Children Hospital from June 2020 to October 2025. Clinical data were collected of the 132 850 newborns and 5 confirmed SMA patients, including general characteristics, validation results via multiplex ligation-dependent probe amplification (MLPA), disease-modifying treatments, and motor function assessments. The carrier rate of survival motor neuron 1 (SMN1) gene exon 7 deletion and the incidence of SMA in Foshan were determined. Changes in muscle strength and motor milestones of confirmed SMA patients before and after early disease-modifying therapy were analyzed. Results: Of the 132 850 screened newborns, 2 378 cases were identified with heterozygous deletion of SMN1 exon 7, and 5 cases with homozygous deletion of SMN1 exon 7 (confirmed as SMA patients via MLPA). The carrier rate of SMN1 exon 7 deletion in Foshan newborns was 1/56 (2 383/132 850), and the SMA incidence (homozygous deletion of SMN1 exon 7) was 1/26 570 (5/132 850). Among the 5 diagnosed patients, 4 had 2 copies of SMN2 exon 7. One patient (case 1) did not receive disease-modifying therapy and died at 2 months of age, while 3\ other patients (case 2, 3, 4) all received disease-modifying therapy before 1.5 months of age. After treatment, their muscle strength improved, and they achieved the motor milestones of walking with assistance, sitting with support, and standing with support. Among the 5 confirmed patients, case 5 had 3 copies of SMN2 exon 7 and received disease-modifying therapy at 1.1 months of age. No obvious muscle strength abnormality was observed before or after treatment, and this patient achieved independent walking at 13 months of age. Conclusions: The carrier rate of SMN1 gene exon 7 deletion among newborns in Foshan is low, and the incidence of SMA (homozygous deletion type of SMN1) is also low. Early newborn screening for SMA, along with early diagnosis and treatment, can effectively improve the motor function in affected infants.