Sporadic progressive myoclonic epilepsy with early-onset dementia caused by a de novo mutation in PSEN1

Progressive myoclonic epilepsy contains wide variety of diseases in which differential diagnosis is challenging. Here, we report a 36 year-old female patient presenting with sporadic myoclonic epilepsy and cognitive decline. Cerebrospinal fluid analysis revealed increased level of total tau and phosphorylated tau and decreased level of amyloid beta-42 protein, although the extent was modest. Whole-exome sequencing analysis revealed a known heterozygous de novo mutation p.Phe177Ser in PSEN1, a causative gene for familial Alzheimer's disease. A previously reported pedigree with the same mutation presented with similar phenotypes, indicating genotype-phenotype correlation. This report illustrated that familial Alzheimer's disease with PSEN1 mutations should be considered in the differential diagnosis of progressive myoclonus epilepsy.