Thymic alymphoplasia, monoclonal gammopathy, and Pneumocystis carinii pneumonia in an infant.

Immunological deficiencies have been shown in many children bearing thymic malformations. In some children both cell-mediated and humoral immune reactions have been depressed, the former indicated by abnormalities of delayed hypersensitivity and of homograft rejection, and the latter by deficient antibody responses and hypo-y-globulinaemia. Such findings are in accord with the experimental evidence that the thymus acts as a 'protagonist in the development of immunological capacity' (Holborow, 1967). Unfortunately, the inconstancy of these deficiencies in other cases has prevented a more precise definition of the role of the thymus in human immunogenesis. Not all children with congenital thymic defects have been hypo-y-globulinaemic, though the patterns of immunoglobulin synthesis in these exceptions have varied widely and have often been abnormal. The infant with thymic dysplasia who is the subject of this report presented a further variation in having an immunoglobulin with the restricted electrophoretic and antigenic properties characteristic of the M-type proteins found in multiple myeloma and related neoplastic diseases.