Prognosis in hereditary amyotrophic lateral sclerosis.

Two different forms of hereditary amyotrophic lateral sclerosis (ALS) has been separated according to duration of illness. A rapid course with short survival as seen in sporadic ALS is usual, but a comparatively benign type with a mean survival of 12 years has been reported in some families. Four patients from an ALS-afflicted family with five affected members in three generations were examined and then followed up. A conspicuous variability in progression among the patients was observed, with death occurring from 26 months to 12 years after onset; one patient is alive 13 years after onset. Wide differences were also found with respect to initial site of involvement and pyramidal tract signs. Three other families with this mixed pattern of prognosis have been reported previously. Affected individuals within involved families had either short or long duration of the disease, rather than displaying a continuum. However, in view of the existence of a type of hereditary ALS with marked intrafamilial variability, prognosis, even in the presence of previous benign cases, should be cautiously given.