The recent description by Rippon et al1 of 2 brothers with early-onset Alzheimer disease associated with the M139V mutation in the presenilin 1 (PSEN-1) gene raises some interesting points about genotype-phenotype correlations in this disease. Their findings concur with other recent analyses of M139V, which have noted intrafamilial homogeneity and interfamilial heterogeneity with respect to age at onset, disease duration, and clinical and neuropathological features.2,3 Behavioral and psychiatric features, although less notable in other M139V cases than in the siblings described by Rippon and colleagues, have been reported in pedigrees with other PSEN-1 mutations and have sometimes been of sufficient prominence to suggest a clinical diagnosis of frontotemporal dementia (as in the L113P4 and V89L5 mutations).
Larner AJ. Genotype–Phenotype Correlation in Early-onset Alzheimer Disease With Presenilin 1 Gene Mutations. Arch Neurol. 2004;61(5):801. doi:10.1001/archneur.61.5.801-a