100th anniversary of Perusini's second case: patient RM and his kindred.

The first 4 cases of Alzheimer's disease published by Alois Alzheimer's laboratory were authored by the young Italian physician Gaetano Perusini. In his discourse, ''Uber klinisch und histologisch eigenartige Erkrankungen des späteren Lebensalters'' Perusini describes 4 cases of histological and clinical findings of peculiar psychiatric diseases of older age. With regard to case number II, Perusini remarks ''since 1899 RM has psychically changed.'' As RM is said to be 45 years of age on admission, this would imply the obvious onset of disease at the early age of 37. A detailed analysis of archival material revealed that RM was actually 10 years older. Perusini's hint that ''one of the patient's brothers does not seem to be normal'' initiated our search for this individual to rule out an autosomal dominant inheritance in this kindred. We initiated genealogical studies over 8 generations to get more detailed information about this early case of psychiatric history.