Autoimmune myelofibrosis is a rare, distinct clinicopathological entity that can occur in isolation (primary) or in association with systemic autoimmune disorders (secondary), such as systemic lupus erythematosus and Sjogren's syndrome. This disease is characterized by isolated or combined chronic cytopenias associated with autoimmune phenomena and bone-marrow fibrosis. Due to the rarity of this disease, patients are frequently misdiagnosed as having primary myelofibrosis, the most common form of bone-marrow fibrosis. Distinguishing between both disease entities is essential given the drastic therapeutic and prognostic differences between both disorders. We report a case of primary autoimmune myelofibrosis presenting with severe isolated anemia refractory to multiple lines of therapy. This patient was initially misdiagnosed as primary myelofibrosis. The absence of the characteristic features of primary myelofibrosis and the lack of a clonal abnormality on cytogenetic and molecular studies, particularly JAK2, CALR, and MPL mutation analyses, confirmed the absence of an aberrant neoplastic process. Furthermore, the presence of monoclonal T-cell receptor gamma gene rearrangements delineated the presence of an autoimmune disorder supporting our diagnosis of primary autoimmune myelofibrosis.