MOLECULAR CONFIRMATION OF GERM-LINE MOSAICISM FOR A SUBMICROSCOPIC DELETION OF CHROMOSOME 22Q11

Submicroscopic deletions of chromosome 22q11 have been reported in a m ultiple anomaly syndrome variously labelled as velocardiofacial syndro me, conotruncal anomaly face syndrome, and Di George syndrome. Most 22 q11 microdeletions occur sporadically, although in some cases the dele tion may be transmitted. We describe two affected sibs with confirmed 22q11 deletions from unaffected parents who are not deleted. Haplotype analysis demonstrates that the deletion in the affected sibs has occu rred on the same maternal chromosome 22. Furthermore, an unaffected si b was found to have inherited the same maternal haplotype at 22q11 in an undeleted form. This is the first molecular demonstration of germ l ine mosaicism for a microdeletion at chromosome 22q11 and highlights t he need for caution in estimation of recurrence risks, even when const itutional deletions have been excluded on parental analysis. Am. J. Me d, Genet, 78:103-106, 1998, (C) 1998 Wiley-Liss, Inc.