Progression rate and age at onset are related in autosomal dominant neurologic diseases.

We found that the rate of progression of two adult hereditary neurologic disorders (dominant ataxia and Huntington disease) correlated inversely with the age at onset. The earlier the onset, the more rapid the course; the later the onset, the slower the course. Alzheimer disease/senile dementia followed a similar pattern. The rate of progression of a nonhereditary progressive neurologic disorder, ALS, showed the opposite trend.