Microdeletion of chromosome 1q21.3 in fraternal twins is associated with mental retardation, microcephaly, and epilepsy.

Reported here are twins, both of whom have a 1q21.3 microdeletion and who exhibit key features common to previously reported cases such as microcephaly and developmental delay. However, some clinical findings and deleted genes differed from those in previously reported cases. The karyotype was normal 46, XX for both of the twins. Array comparative genomic hybridization (CGH) identified a 2.6 Mb deletion on chromosome 1q21.3 (chr1: 153,514,121-156,171,335 bp) in case 1 and a 1.6 Mb deletion on chromosome 1q21.3 (chr1: 154,748,365-156,358,923 bp) in case 2. The deleted region includes DPM3, MUC1, GBA, PKLR, RIT1 , and LAMTOR2 in both siblings. To the extent known, this is the second report of a 1q21.3 microdeletion in a family with mental retardation, developmental delay, seizures, and some dysmorphic features, thus expanding the phenotypic spectrum.