Primary autoimmune myelofibrosis: definition of a distinct clinicopathologic syndrome.

Myelofibrosis is characterized by reticulin fibrosis of the bone marrow with resulting features of myelophthisis. Besides hematopoietic malignancies and other neoplasms involving the bone marrow, myelofibrosis has been described in association with autoimmune disorders, especially systemic lupus erythematosus. We describe the clinicopathologic features of a primary form of autoimmune myelofibrosis (AIMF) in patients who do not have systemic lupus erythematosus or another well-defined autoimmune syndrome. Absence of marked splenomegaly, peripheral blood cytopenias with mild teardrop poikilocytosis and leukoerythroblastosis, bone marrow lymphoid aggregates, and presence of autoantibodies are some of the salient features of primary AIMF. AIMF should especially be differentiated from chronic idiopathic myelofibrosis, a neoplastic myeloproliferative disease. Primary AIMF appears to have an excellent prognosis, with all patients reported in this series responding to a short course of corticosteroid therapy.