Hoffmann (1894) described slowly progressive juvenile amyotrophic lateral sclerosis with concomitantly progressive dementia in 4 sibs. Staal and Went (1968) described 7 sibs (out of 15), offspring of a first-cousin marriage, affected by the same disorder. Three boys ... Hoffmann (1894) described slowly progressive juvenile amyotrophic lateral sclerosis with concomitantly progressive dementia in 4 sibs. Staal and Went (1968) described 7 sibs (out of 15), offspring of a first-cousin marriage, affected by the same disorder. Three boys and 4 girls were affected. Death had occurred in 5 of 7 sibs at intervals varying from 9 to 21 years after onset of symptoms which started at about age 10 years. McKusick (1986) noted that he had seen 4 cases of ALS-dementia complex in 2 related and inbred Old Order Amish sibships. The disorder is probably distinct from that observed in another Amish group (see 205100), being distinguished mainly by the associated dementia.