Unusual chromosomal mosaicism in Wolf-Hirschhorn syndrome: del(4)(p16)/der(4)(qter-q31.3::pter-qter)

Abstract

We report on the unusual cytogenetic findings in a girl with moderate mental retardation and a mosaic karyotype 46,XX,del(4)(p16)/46,XX,der(4)(qter-q31.3::pter-qter). The facial features observed in the child initially did not suggest the diagnosis of Wolf-Hirschhorn syndrome (WHS), but the distinct facial gestalt became obvious at prepubertal age. Fluorescence in situ hybridization (FISH) analysis with different probes that map to 4p and 4q helped to clarify the karyotype. We discuss the mechanism of appearance of this unusual type of mosaicism, which has not been reported before.