CD4 and severe combined immunodeficiency: 7 of 57 (12%) cases were identified with isolated T cell lymphopenia (selective deficiency of CD4+ T cells (n = 6) or CD8+ T cells (n = 1) and were eventually grouped under the category “Combined Immunodeficiency (CID) generally less profound than Severe combined Immunodeficiency” according to the IUIS classification (9).