DiGeorge’s Syndrome (Thymic Aplasia)

DiGeorge’s Syndrome (Thymic Aplasia)

DiGeorge’s syndrome (DGS) is secondary to a hemizygous deletion of the short arm of chromosome 22 (DEL 22q. 11.2). This chromosomal defect causes a com-plex inherited syndrome characterized by cardiac malformations, thymic hypopla-sia, palatopharyngeal abnormalities with associated velopharyngeal dysfunction, hypoparathyroidism, and facial dysmor-phism. The 22q deletion has an incidence of approximately 1 in 2,500 live births. The associated clinical phenotype is highly variable. About 20 percent of individu-als with 22q deletion have thymic aplasia, resulting in T lymphopenia and impaired CMI. In most such cases, the degree of T lymphopenia is modest (partial DGS) and almost complete restitution of the T-cell repertoire and function occurs by two years of age. Therefore, infections characteristic of T-cell deficiency are rare in these indi-viduals. A minority of infected individuals