Polymyositis in a patient with thymoma and T cell lymphocytosis

A patient presenting with agranulocytosis and lymphocytosis (4600/mm3) was found subsequently to have polymyositis (PM) and a thymoma. Immunophenotyping of the circulating lymphocytes revealed mature T cells (CD3, CD5, CD7 positive) with normal proportions of both CD4 (55%) and CD8 (38%) positive cells. PM was confirmed by electromyogram and muscle biopsy. Fewer than a dozen cases of thymoma and T cell lymphocytosis have been reported and ours is the first in which autoimmune manifestations have been noted. The presence of lymphocytosis in a patient with PM should prompt the search for a thymoma.