DiGeorge Syndrome is a genetic disorder caused by the deletion of a small section of chromosome 22. This results in a midline congenital defect including thymic aplasia, or congenital deficiency of a thymus.
Patients may present with a profound immunodeficiency disease, due to the lack of T cells. No other immune cell lineages are affected by the congenital absence of the thymus.
DiGeorge Syndrome is the most common congenital cause of thymic aplasia in humans.