Unilateral diffuse white matter involvement in a patient with atypical FMR1 mutation.

A 62-year-old man without relevant medical history visited our emergency department with seizure. His brain MRI revealed diffuse high signal intensity in the white matter with some cortical involvement in the dorsolateral prefrontal area and middle frontal gyrus on FLAIR sequence, which were only confined to the left hemisphere. In his whole exome sequencing, a hemizygous variant, NM_001185081.1:c.1216C>T, was detected on FMR1 gene of Xq27.3, which creates a stop codon at codon 406 in exon 13. The variant is classified as pathogenic according to the recommendation of ACMG/AMP guideline. This is the first case report of the patient presenting with seizure, who had a pathogenic variant on FMR1 gene with diffuse cerebral white matter involvements in the unilateral hemisphere.