PURE RED-CELL APLASIA ASSOCIATED WITH MALIGNANT THYMOMA, MYASTHENIA-GRAVIS, POLYCLONAL LARGE GRANULAR LYMPHOCYTOSIS AND CLONAL THYMIC T-CELL EXPANSION

A case with the triad of pure red cell aplasia (PRCA), myasthenia grav is, and malignant thymoma is reported. There was a clonal proliferatio n of T cells within the thymoma, as demonstrated by a T cell antigen r eceptor (TCR)G chain gene rearrangement. However, despite a large gran ular lymphocytosis, clonality could not be shown in the peripheral blo od either before or after thymectomy. There was no evidence of human T cell lymphotrophic virus type 7 (HTLV1) infection. It is postulated t hat the clonal thymic T cell population secreted cytokine(s), which st imulated the polyclonal proliferation of large granular lymphocytes, w hich in turn suppressed erythropoiesis. Thymectomy removed the stimulu s to the large granular lymphocytes and hence there was a resurgence o f erythropoiesis.