Four cases of JFALS in a family, with mean age at onset of 15.7 years and exceptionally long survival (mean, 27 years), are reported from the National Institute of Neurology and Neurosurgery, Mexico City. The father developed the classic form of ALS at 63 and died 2 years later. Three of the children had severe, and one moderate, dementia in adulthood. Cognitive deterioration began a few years after onset. MRI in one patient showed severe atrophy of cortex and brain stem, but the classic pyramidal degeneration was slight. 
COMMENT. A juvenile form of familial ALS has an onset in late childhood and a long survival, complicated by dementia. Genetic analysis in FALS show 20% linked to chromosome 21q21, and the remaining 80% unidentified.