[Prednisone-responsive pure red cell aplasia associated with polymyalgia rheumatica]

Pure red cell aplasia (PRCA) is a rare disorder characterized by selective failure of erythropoiesis. Acquired PRCA can occur secondary to autoimmune diseases; however, an association with polymyalgia rheumatica (PMR) is extremely rare. This report describes a case of PRCA considered to be secondary to PMR. A 63-year-old man presented with severe anemia and was diagnosed with PRCA based on bone marrow findings. Extensive investigations revealed no underlying disease, leading to an initial diagnosis of idiopathic PRCA. Cyclosporine treatment resulted in only transient improvement. Over the clinical course, the patient developed fever, shoulder and hip girdle pain, and elevated inflammatory markers, leading to a diagnosis of PMR. After initiation of prednisone therapy, both PMR-related symptoms and anemia rapidly improved, and no relapse occurred after discontinuation of cyclosporine. Based on the temporal association and treatment response, the PRCA was considered to be secondary to PMR. This case highlights a rare but important association between PMR and PRCA.