Slowly progressive autosomal dominant spastic paraplegia with late onset, variable expression and reduced penetrance: a basis for diagnosis and counseling.

We have examined a pedigree in which familial spastic paraplegia (FSP) is segregating in four generations. The data show a high rate of transmission of the trait, late onset, reduced penetrance, variable age and symptom expressivity, and an autosomal dominant mode of transmission. A summary of our data together with the FSP data of other shows a 1:1 transmission from males and from females, and an overall 1:1 transmission ratio. The risks for the children of symptomatic and non-symptomatic parents are illustrated.