White blood cell aplasia associated with thymoma.

A limited number of cases of acquired hypoplastic neutropenia or pure white blood cell aplasia (PWCA) associated with thymoma have been reported, in contrast to the well-documented association of pure red blood cell aplasia and thymoma. The mechanism of the aplasia in these disorders is unclear. The authors report a case of PWCA (with total absence of all granulopoietic elements in the bone marrow) in a patient with metastatic spindle cell thymoma, in which suppression of autologous granulocyte-macrophage colony-forming units by the patient's serum could be demonstrated. This finding suggests a humoral autoimmune mechanism for the pathogenesis of PWCA in this patient and lends support to the possibility that all hematologic phenomena associated with thymoma may have an autoimmune basis.