We describe the phenotype of a Bulgarian early-onset Alzheimer's disease (EOAD) family with 3 affected patients in 3 generations. In the proband, a novel L381V mutation in the presenilin1 (PSEN1) gene was identified. In this patient, the first symptoms were noticed at the age of 32 years and she died at the age of 37 years. The EOAD phenotype caused by the novel L381V mutation in the PSEN1 gene presented clinically, by a very early onset in the proband, rapid progression of dementia, spastic paraparesis, and extrapyramidal signs, as atypical clinical signs in Alzheimer's disease patients.