Testing SMA patient DNA with advanced methods like HapSMA can reveal genetic changes that affect how severe the disease is, ...

A tablet taken by mouth, it causes the body to boost the activity of a second gene, called SMN2, which also carries the instructions for building SMN protein but typically makes less than SMN1.

In general, each corresponds to the copy number of the SMN2 gene, which produces a small fraction (~10%) of functional SMN protein, essential to the survival of motor neurons, compared with SMN1.

Risdiplam works by targeting the SMN2 gene to induce increased production ... Types 1 through 4 are linked to a mutation in both copies of the SMN1 gene (on chromosome 5), which leads to few ...