BACKGROUND/AIMS: Mutations in the amyloid precursor protein gene were the first 
to be recognized as a cause of Alzheimer's disease (AD).
METHODS: We describe 2 Italian families showing the missense mutation in exon 17 
of the amyloid precursor protein gene on chromosome 21 (Val717Ile), known as 
London mutation.
RESULTS: In 1 family, this mutation was responsible for AD in 3 out of 7 
siblings and it is also present in a fourth sibling who has only shown signs of 
executive dysfunction so far. Two subjects of the other family with AD diagnosis 
were carriers of the same mutation.
CONCLUSION: All AD subjects showed a cognitive profile characterized by early 
impairment in long-term memory, shifting abilities and affective symptoms 
beginning in the fifth decade of life.