Phenotypic heterogeneity in Alzheimer's disease.

Probable heterogeneity of Alzheimer's disease is still debated. Many authors report heterogeneity on phenotypic and/or genetic level. We have tried to reveal if variability exists also in an Italian kindred (family N) with early onset Alzheimer's disease in which the illness has been transmitted in a mendelian autosomal fashion since the early eighteenth century. The only parameter that varies widely is the age at death of affected members and it was taken as an index of expression, a measure of phenotypic variability. Extension of this concept will be discussed.