Spinal Muscular Atrophy
What is SMA?
Spinal muscular atrophy is a degenerative problem that affects the motor nerves, resulting in muscle wasting and weakness.
Spinal muscular atrophy occurs in approximately one in 6,000 -10,000 live births.
What causes spinal muscular atrophy?
SMA is an autosomal recessive disease. This means that two abnormal copies of the gene, one inherited from each parent, are necessary to have the condition. Boys and girls are affected with equal frequency. A child who inherits only one abnormal gene copy is a carrier, and is not at risk to develop symptoms.
A gene called survival motor neuron (or SMN) is found to have an abnormal area (called a deletion) in over 95 percent of cases of SMA. Symptomatic individuals of all ages can be tested through DNA studies typically done from a blood sample.
When both parents are carriers, there is a one in four, or 25 percent, chance, with each pregnancy, to have a child with SMA. Carrier testing of parents can help determine the recurrence risk in a specific family.