FMR1 fuiiy expanded mutation with minimal methylation in a high functioning fragile X male

Abstract Cytogenetic and molecular genetic anal-ysis of a peripheral blood sample from a 31 year old, non-mentally retarded male with a family history of fragile X syndrome showed unexpected results. Nine percent of cells evaluated cytogenetically ex-pressed a fragile X chromosome and mo-lecular examination of the FMR1 gene showed a highly unusual pattern defined as a minimally methylated fully expanded mutation. This case illustrates the need to recognise exceptional variations of fragile X syndrome mutations.