T-cell deficiency in diGeorge syndrome.

DiGeorge syndrome is broadly defined as absence or hypoplasia of the thymus due to dysmorphogenesis of the third and fourth pharyngeal pouches in early embryonic life. Various tests of thymic function have been evaluated in some 19 infants and young children with this syndrome. Deficiency of T lymphocytes has been shown to occur in the presence of as much as 10 to 20% of the normal amount of histologically normal thymic tissue in the partial DiGeorge syndrome.