A mosaic case of isodicentric chromosome 18.

A case of mosaicism of isodicentric chromosome 18 is reported. Dicentric chromosome 18 occurs rarely and only five cases of isodicentric chromosome 18 have been documented. A high resolution banding method revealed that the karyotype of the patient was mos 46,XX/46,XX idic(18)(pter-->q21.3::q21.3-->pter), and the ratio of normal and abnormal clones was 1:1. The clinical manifestations, resembling those of trisomy 18 syndrome, were affected by both partial trisomy 18pter-->q21.3 and partial monosomy 18q21.3-->qter.