Prenatal diagnosis of an unexpected interstitial 22q11.2 deletion causing truncus arteriosus and thymic hypoplasia in a ring 22 chromosome derived from a maternally inherited paracentric inversion

Abstract

The ring chromosome 22 found in the fetus appears to have been derived from a rearrangement of the mother's inverted 22, resulting in ring formation and loss of the end of the distal long arm of the inverted 22, including the TUPLE1 locus, causing DiGeorge syndrome in the fetus. The apparent interstitial deletion was actually a terminal deletion in a maternally inherited rearranged chromosome 22.