The Italian ITASMAC network dedicated to spinal muscular atrophy (SMA) studied 169 individuals, children or adults, with a homozygous deletion of the SMN1 gene and four copies of the SMN2 gene, and not treated by innovative therapy:
- the sex ratio showed a clear male predominance (102/169),
- 6 patients were presymptomatic children, 8 had type II SMA, 145 had type IIIA and 107 had type IIIB,
- 2 patients, identified as part of a family survey, were totally asymptomatic adults,
- more than a third of type III patients had lost their ability to walk, and, rather unexpectedly, a quarter of type IV patients suffered the same fate, despite the fact that type IV SMA is classically considered to have very little progression.
These findings will be important to take into account, particularly in the context of neonatal screening for SMA, which is currently being rolled out across the world.
