A Case of Rare Autoimmune Pancytopenia Due to Graves’ Disease

Abstract

Introduction: Graves’ disease has been associated with cytopenias, most commonly anemia. Pancytopenia is a rare complication and is not often encountered.Case Presentation: A 54-year-old woman with history of multiple sclerosis on alemtuzumab was referred for abnormal thyroid function tests. At the initial visit, the patient reported a 20-pound unintentional weight loss, tremors, sweating and heat intolerance. She was 3 years post-menopausal and had no history of recent viral illness, contrast exposure or family history of thyroid disease. Physical exam revealed an anxious appearing woman with fine tremors in both hands, hyperreflexia but no lid lag or exophthalmos. Labs included TSH <0.005 uIU/mL (0.400-4.2), free T4 2.89 ng/dL (0.80-1.50), TSH receptor binding antibody 8.24 IU/L (< 2.00), TSI 7.27 IU/L (<0.56), WBC 2900/uL (4500-11000), ANC 1746/uL (1900 - 8000), hemoglobin 11.4 g/dL (11.7-15.0) and platelet 207,000/uL (150,000-450,000). Thyroid ultrasound noted sub-centimeter hypoechoic/cystic nodules and 24-hour thyroid uptake showed 56.4% symmetric uptake (upper limit of normal 30%). Due to leukopenia, the patient was started on propranolol and underwent radioiodine ablation with 14.8 mCI. Two weeks later, she reported easily bruising and gum bleeding and her blood work was significant for pancytopenia. The patient was referred to hematology and two bone marrow samples were obtained. Though MDS/MPN was initially suspected based on atypia in both specimens, there were no immunophenotypic, cytogenetic or molecular abnormalities suggesting a neoplastic process. Instead the patient was thought to have autoimmune pancytopenia secondary to Graves’ and the atypia was believed to be secondary to peripheral consumption. She was started on prednisone 1 mg/kg/day with resolution of her cytopenias.Discussion: Graves’ disease has been associated with hematological abnormalities including isolated anemia (the most common), thrombocytopenia or leukopenia. Pancytopenia is an uncommon complication and is rarely described in the literature. The exact mechanism remains unclear, but may be related to either reduced production of hematopoietic cells from the bone marrow or increased destruction of mature hematopoietic cells due to autoantibodies. Since thyroid hormones are known to increase erythropoietin, this leads to an exaggerated consumption of iron, folic acid and vitamin B12 and can cause various forms of anemias. Leukopenia may be secondary to immunologic destruction whereas thrombocytopenia may be due to antiplatelet antibodies or increased splenic sequestration. Pancytopenia is rare. Our patient was treated with high dose prednisone with resolution of her pancytopenia, which suggests an autoimmune process as the mechanism. Our case showcases a rare complication of Graves’ disease and highlights that high dose steroid therapy may improve cytopenias associated with this condition.