We studied the potential role of APOE ε4 in modifying phenotypic diversity in EPM1, given its established association with neurodegeneration, particularly in Alzheimer's disease.<h4>Methods</h4>APOE genotypes were determined for 65 genetically verified EPM1 patients homozygous for the CSTB expansion mutation. This evidence concerns the gene CSTB and early-onset autosomal dominant Alzheimer disease.