Outcomes of genetic testing and prenatal diagnosis of spinal muscular atrophy in Jordan.

BACKGROUND

Spinal muscular atrophy (SMA) is a life-threatening, neuromuscular disease caused by variants in the survival motor neuron 1 (SMN1) gene, which affects spinal motor neurons resulting in progressive muscle weakness and hypotonia. This study aimed to identify the genetic diagnosis of SMA, present the outcomes of prenatal diagnosis, and provide an estimate for a minimum prevalence of the disease in Jordan.

METHODS

From 2007 through 2024, a total of 413 patients clinically suspected to have SMA and 243 at-risk prenatal cases were studied using diagnostic molecular testing. SMN1 exons 7 and 8 deletions were analyzed using either polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) (patients: n = 308, fetuses: n = 194) or multiplex ligation-dependent probe amplification (MLPA) (patients: n = 105, fetuses: n = 49). The copy number of SMN2 was determined for patients tested by MLPA.

RESULTS

Homozygous deletion of SMN1 exon 7 was identified in 59.3% (245/413) of patients. Among them, 73.5% (n = 180) had SMA type I, 22.9% (n = 56) type II, and 3.7% (n = 9) type III. MLPA confirmed the diagnosis in 60% (63/105) of patients, with SMN2 copy numbers correlating with disease severity. A minimum prevalence of SMA was predicted to be 2.09 per 100,000 population with an incidence of 0.73 per 10,000 live births. Results on prenatal diagnostic cases showed 70.8% (172/243) of fetuses were unaffected.

CONCLUSIONS

The study highlights the importance of SMA as a clinical health problem in Jordan and demonstrates MLPA as a reliable diagnostic tool. Our findings support the integration of SMA carrier screening into national newborn screening and premarital programs to enable early diagnosis, improve genetic counseling, and facilitate gene therapy options, ultimately improving overall patient outcomes and management.