Abnormal B-cell proliferation associated with combined immunodeficiency, cytomegalovirus, and cultured thymus grafts.

A male infant in whom multiple recurrent multiorgan infections developed during the first six months of life was found to have combined immunodeficiency. Progressive pulmonary disease developed at age two years; cytomegalovirus (CMV) was isolated from the respiratory tract and urine. Three separate intramuscular grafts of cultured thymus fragments did not produce change in the course of the illness. Soon after age three years, IgG lambda appeared in the serum as an M-component. The patient died at age three and one-half years, with respiratory insufficiency due to pulmonary fibrosis. At autopsy, a malignant plasma cell infiltrate was limited to the retroperitoneum. The infiltrate replaced lymph node structures and surrounded nerve fascicles, which appeared necrotic, and contained CMV inclusions in ganglion cell nuclei. The plasma cells showed strong monoclonal staining for IgG lambda. Also noted was positive staining for J-chain, which has been reported previously in malignant plasma cells producing IgG. CMV could be responsible for abnormal B-cell proliferation in patients with defective immunoregulation who receive immunotherapy, as in lymphoid abnormalities associated with Epstein-Barr virus.