Pure red cell aplasia (PRCA) is defined as anemia in the presence of severe reticulocytopenia and absent or markedly decreased erythroid precursors in the marrow. When associated with another disease entity, it is classified as secondary acquired PRCA. A rare entity, thymolipoma, which constitutes 2% to 9% of thymic tumors has been associated with PRCA in some studies. The prevalence of thymolipoma among patients with myasthenia gravis reaches 43.8%. This paper presents the rare presentation of myasthenia gravis associated with thymolipoma and PRCA.

We present the case of a 64-year-old female who was diagnosed with myasthenia gravis and has been on maintenance pyridostigmine (Mestinon) for 12 years. She presented with symptoms of anemia and became transfusion requiring. Routine chest CT showed a thymic mass which was confirmed to be a thymolipoma during biopsy. Bone marrow studies confirmed the absence of erythroids, hence the diagnosis of secondary acquired PRCA.

There have been case reports associating PRCA with thymolipomas. Thymolipomas, which constitute 2% to 9% of thymic tumors are found among patients with myasthenia gravis, but the majority remains asymptomatic despite increasing tumor size. PRCA with associated thymic mass shows improvement of symptoms with tumor removal and immunosuppression. Oral corticosteroids result in a response rate of 39% while cyclosporine results in 77% response. This can be tapered off once response has been achieved.

This case report emphasizes the importance of early bone marrow studies among patients with myasthenia gravis presenting with sudden onset anemia.