Spinal Muscular Atrophy (SMA)

Principle assay is divided into two steps: 

• A first extraction step through the addition of two buffers and an incubation step. This step can be automatized via NEO-M-300 by Hamilton. 
• A second DNA amplification step via qPCR. 

The management of anterior spinal muscular atrophy (SMA) in newborns has evolved significantly over the last few years. Therefore, implementation of a spinal muscular atrophy screening program in newborns has quickly become medical-economic evidence in many countries.

Spinal muscular atrophy is a rare neuromuscular disease characterized by progressive muscle weakness caused by premature loss of anterior motor neurons of the spinal cord and brainstem nuclei.

The disease is associated, in almost 95% of cases, with a homozygous deletion of exon 7 of the SMN1 gene, a gene located on chromosome 5 (5q12.2-q13.3). This deletion hinders SMN protein synthesis, which is essential for survival of motor neurons. Approximately 5% of patients with SMA carry a heterozygous deletion of exon 7 from SMN1 combined with a point mutation in the second allele (i.e., Composite heterozygous).

The clinical severity of SMA is closely linked to the presence of a second gene, SMN2. This pseudogene, having more than 99% homology with the SMN1 gene, only produces approximately 10% functional SMN protein. The phenotype of SMA patients is thus found to be less severe and more slowly evolving as the number of copies of the SMN2 gene is high.