Decreased size of paracoical areas of lymph nodes is expected as this child has DiGeorge Syndrome. DiGeorge Syndrome: Deficient CMI is seen due to aplasia of thymus and hence deficiency of T cells. This leads to paracoical areas of lymph nodes and periaeriolar sheaths of the spleen being reduced in size. B cells are usually not affected. Clinical Features of DiGeorge Syndrome - DiGeorge syndrome is a cellular immunodeficiency disorder caused by the deletion of a small segment of chromosome 22 (22q11) leading to a developmental defect involving the endodermal derivatives of the third and fouh pharyngeal pouches. (Thymus and parathyroid glands) The clinical features can be remembered with the mnemonic - CATCH C - Cardiac defects A - Abnormal facies T - Thymic aplasia C - Cleft palate H - Hypocalcemia Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition