What Causes ALS? — Page 2

The genetic link to ALS

About 5 to 10 percent of people with ALS have family members with the disease. This inherited form of the disease is called familial ALS. It stems from gene mutations that pass down through generations. Only one parent needs to have the mutated gene for his or her child to inherit it.

The gene associated with 30 to 40 percent of familial ALS cases is called C9orf72. It codes for the production of a protein, found in a part of neurons (nerve cells), that sends and receives signals to and from other nerve cells. The same genetic mutation has been associated with frontotemporal dementia (or FTD) — a group of related dementias that impair mental function, personality, and motor skills.

Mutations to the SOD1, TARDBP, and FUS genes cause a smaller number of inherited ALS cases. All of the genes associated with ALS are essential to the health of motor neurons. Damage to these nerve cells leads to muscle weakness and other amyotrophic lateral sclerosis symptoms.

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