Partial monosomy and partial trisomy 18 in two offspring of carrier of pericentric inversion of chromosome 18

Abstract

A pericentric inversion of chromosome 18 is described in the mother of a patient with clinical diagnosis of 18q- syndrome. The propositus' chromosome complement includes the recombinant 18 with deficiency of the distal one third of the long arm and duplication of the terminal segment of the short arm. The propositus' sister carries the recombinant 18 with a duplication of the distal one third of the long arm and a deficiency of the terminal segment of the short arm. The relative length of the inverted segment represents about 60% of the total chromosome 18 length. The probability of recombinant formation following the occurrence of a chiasma within the inverted segment is predicted to be high.