DiGeorge syndrome is thymic and parathyroid hypoplasia or aplasia leading to T-cell immunodeficiency and hypoparathyroidism.
DiGeorge syndrome results from gene deletions in the DiGeorge chromosomal region at 22q11, mutations in genes at chromosome 10p13, and mutations in other unknown genes, which cause dysembryogenesis of structures that develop from pharyngeal pouches during the 8th wk of gestation. Most cases are sporadic; boys and girls are equally affected. DiGeorge syndrome may be partial (some T-cell function exists) or complete (T-cell function is absent).
Infants have low-set ears, midline facial clefts, a small receding mandible, hypertelorism, a shortened philtrum, and a congenital heart disorder. They also have thymic and parathyroid hypoplasia or aplasia, causing T-cell deficiency and hypoparathyroidism. Recurrent infections begin soon after birth, but the degree of immunodeficiency varies considerably, and T-cell function may improve spontaneously. Hypocalcemic tetany appears within 24 to 48 h of birth.
Prognosis often depends on severity of the heart disorder.
Diagnosis is based on clinical findings. An absolute lymphocyte count is done, followed by B- and T-cell counts if leukopenia is detected; blood tests to evaluate T-cell and parathyroid function are done. A lateral chest x-ray may help evaluate thymic shadow. Fluorescent in situ hybridization (FISH) testing can detect the chromosomal deletion in the 22q11 region; standard chromosomal tests to check for other abnormalities may also be done. Cardiac catheterization may be needed to identify heart defects.
In partial DiGeorge syndrome, hypoparathyroidism is treated with Ca and vitamin D supplementation; long-term survival is not affected. Complete DiGeorge syndrome is fatal without treatment, which is transplantation of cultured thymus tissue.
Last full review/revision September 2008 by Rebecca H. Buckley, MD