immunology allergic disorders
DiGeorge Syndrome
Diagnosis of DiGeorge Syndrome
Immune function assessment with immunoglobulin (Ig) levels, vaccine titers, and lymphocyte subset counts Overview of Parathyroid Function None Chromosome analysis Diagnosis of DiGeorge syndrome is based on clinical findings. An absolute lymphocyte count is done, followed by B- and T-cell counts and evaluation of lymphocyte subsets if leukopenia is detected. Blood tests to evaluate T-cell and parathyroid function are done. Ig levels and vaccine titers are measured. If complete DiGeorge syndrome is suspected, the T-cell receptor excision circle (TREC) test should also be done. Parathyroid function is assessed by measuring levels of calcium andparathyroid hormone. Low or even low-normal PTH concentration in patients with hypocalcemia is inappropriate and suggests hypoparathyroidism. 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. If DiGeorge syndrome is suspected or patients have manifestations of congenital heart defects, echocardiography is done. Cardiac catheterization may be necessary if patients present with cyanosis. Because most cases are sporadic, screening of relatives is not necessary. 