|What Causes Spinal Muscular Atrophy|
Atrophy is an autosomal recessive disease, which means that both parents
must be carriers. Both parents must have the gene responsible and these
genes must be passed onto their child. When a child has received this gene
from each of its parents it will then be affected by SMA. Although both
parents are carriers the likelihood of passing this gene along to a child
and having an affected child is 25%, or 1 in 4.
Familial Forms (affecting other family members) of Spinal Muscular Atrophy in the older age group can occur as autosomal recessive, mutants or autosomal dominant. The genetic defects underlying these diseases make it necessary to be precise regarding the inheritance pattern in a particular family.