Spinal Muscular Atrophy

Test Description:
Spinal muscular atrophy (SMA) is among the most frequent autosomal recessive diseases with a carrier frequency of 1 in 35 to 1 in 117 depending on ethnicity and an overall incidence of 1 in 10,000 live births. The disease is characterized by the degeneration of alpha motor neurons of the spinal cord anterior horn cells, leading to progressive symmetric weakness, atrophy of the proximal voluntary muscles and infant death. Homozygous deletions of the SMN1 gene on chromosome 5q13 are the most common cause of SMA. Over 95% of SMA patients are missing both copies of SMN1 exon 7 and exon 8 sequences. To test for SMN1 and SMN2 copy number, MLPA analysis is performed.

The carrier frequency for SMA and detection rate of SMN1 copy number analysis differ by ethnicity. The American College of Medical Genetics recommends that carrier screening for SMA be offered to all couples regardless of ethnicity before/during pregnancy.

References:
1. Pearn J. (1980) Classification of spinal muscular atropies. Lancet; I: 919-922.
2. Hendrickson BC, Donohoe C, Akmaev VR, Sugarman EA, Labrousse P, Boguslavskiy L, Flynn K, Rohlfs EM, Walker A, Allitto B, Sears C, Scholl T (2009) Differences in SMN1 allele frequencies among ethnic groups within North America. J. Med. Genet. 46:641-644.

Specimen Requirements:
Two 5-10 ml tubes of anticoagulated blood. The preferred anticoagulant is EDTA (lavendar top tubes), ACD (yellow top) tubes are also accepted.

Shipping: Send at room temperature.

Turnaround Time: 10-14 days

CPT Codes: 83891, 83900, 83901x5, 83909, 83912, 83914x6

Consent and Requisition Forms: Carrier Screening Requisition and Consent [PDF]

Additional Information: General Carrier Screening Brochure [PDF]

Prior to ordering prenatal testing, please contact our laboratory at 212-241-7518 to discuss.