Athymia

Congenital athymia is an extremely rare disorder marked by the absence of the thymus at birth. T cell maturation and selection depend on the thymus, and newborns born without a thymus experience severe immunodeficiency. A significant T cell deficiency, recurrent infections, susceptibility to opportunistic infections, and a tendency to develop autologous graft-versus-host disease (GVHD) or, in the case of complete DiGeorge syndrome, an "atypical" phenotype are characteristics of congenital athymia.