Pathomorphologic findings in severe combined immunodeficiency and reticular dysgenesia.

Pathomorphologic findings in an 11 month old boy with severe combined immunodeficiency (case 1) and in a 4-month old boy with reticular dysgenesia (case 2) are reported. Case 1: The bone marrow exhibited regular granulo-, erythro- and thrombopoiesis. The hypoplastic thymus consisted exclusively of epithelial reticulum cells. The spleen and lymph nodes showed considerable depletion of lymphocytes in both the T- and B-cell areas. There was a complete lack of all lymphatic structures in the gastrointestinal tract and aplasia of the tonsils. Death resulted from Candida sepsis in conjunction with giant cell pneumonia closely resembling Hecht's pneumonia in measles. Case 2: The bone marrow showed a total lack of granulopoiesis. The storngly dysplastic thymus weighed only 1 g. The spleen, the lymph nodes and the gastrointestinal tract exhibited a very strange histologic structure resulting from a complete absence of lymphocytes and plasma cells. The tonsils were aplastic, the para-thyroid glands as well as the other endocrine glands were normally developed. The cause of death was Klebsiella sepsis and Pneumocystis pneumonia, the latter without the characteristic interstitial plasma cell infiltration. The importance of the immune system for activation of the nonspecific mechanisma of defense is discussed with respect to the two types of immunodeficiency states described here.