From Amyotrophic Lateral Sclerosis (ALS)

Amyotrophic lateral sclerosis (ALS), also called Lou Gehrig’s disease or classical motor neuron disease, is a progressive, ultimately fatal disorder that disrupts signals to all voluntary muscles. Many doctors use the terms motor neuron disease and ALS interchangeably. Both upper and lower motor neurons are affected. Symptoms are usually noticed first in the arms and hands, legs, or swallowing muscles. Approximately 75 percent of people with classic ALS will develop weakness and wasting of the bulbar muscles (muscles that control speech, swallowing, and chewing). Muscle weakness and atrophy occur on both sides of the body. Affected individuals lose strength and the ability to move their arms and legs, and to hold the body upright. Other symptoms include spasticity, spasms, muscle cramps, and fasciculations. Speech can become slurred or nasal. When muscles of the diaphragm and chest wall fail to function properly, individuals lose the ability to breathe without mechanical support. Although the disease does not usually impair a person’s mind or personality, several recent studies suggest that some people with ALS may develop cognitive problems involving word fluency, decision-making, and memory. Most individuals with ALS die from respiratory failure, usually within 3 to 5 years from the onset of symptoms. However, about 10 percent of affected individuals survive for 10 or more years.

ALS most commonly strikes people between 40 and 60 years of age, but younger and older individuals also can develop the disease. Men are affected more often than women. Most cases of ALS occur sporadically, and family members of those individuals are not considered to be at increased risk for developing the disease. Familial forms of ALS account for 10 percent or less of cases of ALS, with more than 10 genes identified to date. However, most of the gene mutations discovered account for a very small number of cases. The most common familial forms of ALS in adults are caused by mutations of the superoxide dismutase gene, or SOD1, located on chromosome 21. There are also rare juvenile-onset forms of familial ALS.

From NIH Motor Neuron Diseases Fact Sheet