Thymic hypoplasia is:

DiGeorge Syndrome (Thymic Hypoplasia) DiGeorge syndrome is caused by a congenital defect in thymic development resulting in deficient T-cell maturation. The disorder is a consequence of a developmental malformation affecting the third and fouh pharyngeal pouches, structures that give rise to the thymus, parathyroid glands, and poions of the face and aoic arch.