22q11 deletion syndrome: current perspective

Abstract

Bülent Hacihamdioğlu,1 Duygu Hacihamdioğlu,2 Kenan Delil3 1Department of Pediatric Endocrinology, 2Department of Pediatric Nephrology, GATA Haydarpasa Training Hospital, 3Department of Medical Genetics, Marmara University, School of Medicine, Istanbul, Turkey Abstract: Chromosome 22q11 is characterized by the presence of chromosome-specific low-copy repeats or segmental duplications. This region of the chromosome is very unstable and susceptible to mutations. The misalignment of low-copy repeats during nonallelic homologous recombination leads to the deletion of the 22q11.2 region, which results in 22q11 deletion syndrome (22q11DS). The 22q11.2 deletion is associated with a wide variety of phenotypes. The term 22q11DS is an umbrella term that is used to encompass all 22q11.2 deletion-associated phenotypes. The haploinsufficiency of genes located at 22q11.2 affects the early morphogenesis of the pharyngeal arches, heart, skeleton, and brain. TBX1 is the most important gene for 22q11DS. This syndrome can ultimately affect many organs or systems; therefore, it has a very wide phenotypic spectrum. An increasing amount of information is available related to the pathogenesis, clinical phenotypes, and management of this syndrome in recent years. This review summarizes the current clinical and genetic status related to 22q11DS. Keywords: DiGeorge syndrome, velocardiofacial syndrome, TBX1