Prominent behavioural and psychiatric symptoms in early-onset Alzheimer's disease in a sib pair with the presenilin-1 gene R269G mutation.

Two siblings with the R269G mutation in the presenilin-1 gene causing early-onset Alzheimer's disease are presented, only the second family with this mutation to be reported. Behavioural and psychiatric symptoms were prominent in both cases, as well as cognitive decline. Other reports of presenilin-1 gene mutations associated with behavioural and psychiatric symptoms are reviewed. The distribution of such mutations throughout the presenilin-1 gene argues against specific genotype-phenotype correlations, and suggests a role for other genetic and/or epigenetic factors in the pathogenesis of behavioural and psychiatric features in early-onset Alzheimer's disease associated with presenilin-1 gene mutations.