Genetic basis of DiGeorge and velocardiofacial syndromes.

DiGeorge syndrome and velocardiofacial syndrome have been shown to be associated with microdeletions of chromosome 22q11. More recently, 22q11 deletions have also been detected in individuals with some types of conotruncal cardiac defects as well as conotruncal anomaly face syndrome. Fluorescence in situ hybridization of metaphase chromosomes using cosmid probes from the DiGeorge chromosomal region has been shown to be an efficient method for the detection of 22q11 deletions in at-risk patients, families, and pregnancies. This review summarizes recent cytogenetic, molecular, and phenotypic studies of patients with DiGeorge syndrome and velocardiofacial syndrome as well as recent efforts to identify genes within 22q11 that may play a role in the development of the phenotypic features observed in these disorders.