or Lou Gehrig disease
Degenerative
The disease usually occurs after age 40, more often in men. Most victims die within two to five years from respiratory muscle {{link=atrophy">atrophy . ALS affects motor neuron s; the muscles they control become weak and atrophied, with debility usually beginning in the hands and creeping slowly up to the shoulders. The lower limbs become weak and spastic. Variants include progressive muscular atrophy and progressive bulbar palsy. In 1993 the defective gene that accounts for 5–10% of cases was discovered; it produces an ineffective version of an enzyme that neutralizes free radicals, which destroy motor neurons.