The Omen-syndrome is not a disease on its own, but a complication of congenital SCID. 2. In contrast to patients with classical SCID, patients with Omenn-syndrome possess mature T-cells, which are either of maternal or of host origin. 3. These T-cells are involved in the pathogenesis of the characteristic tissue changes, in particular of skin and lymph nodes (Langerhans-histiocytosis with eosinophilia). 4. The detection of immunodeficiency in Omenn-syndrome is difficult since the lymph nodes are enlarged in contrast to patients with classical SCID. The histomorphological analysis of lymph nodes in Omenn-syndrome is considerably complicated by secondary changes closely resembling dermatopathic lymphadenopathia.
