Spinal muscular atrophy (SMA) is a genetic condition. It is one of the commonest inherited neuromuscular disorder.
Understanding underlying genetics and inheritance
- SMA is inherited as an autosomal recessive condition, which implies that, in most instances an affected child is born since he/ she inherits both mutated copies of the SMN1 gene from the carrier parents, who are unaffected, but has mutation in one of the two copies of the SMN1 gene.
- The carrier frequency is fairly high in the population and an affected child is born due chance marriage of two carriers.
- Testing for the carrier status is not widely available. Paucity of testing facilities compounded with lack of awareness makes it almost impossible to screen and detect carrier status before an affected child is born.
- Moreover, the risk of having an affected child is 25% when both partners are carriers, so many a times, many such families never come to medical attention.