Aplastic anemia secondary to propylthiouracil: A rare and life-threatening adverse effect.

BACKGROUND: Propylthiouracil has been in use for more than half a century for the treatment of hyperthyroidism. While it is largely known to cause agranulocytosis, its association with aplastic anemia is rarely heard of. Our case will be the third in literature to suggest aplastic anemia as a manifestation of propylthiouracil, which unfortunately culminated in the death of the patient. CASE: A 67-year-old female, with recently diagnosed metastatic adenocarcinoma of the lung, developed hyperthyroidism after being started on Nivolumab and Iplimumab. After she developed atrial fibrillation, she was started on propylthiouracil to control the thyroid activity. Soon after that, she was admitted with severe neutropenia, which progressed to pancytopenia confirmed as aplastic anemia on a bone marrow biopsy. Despite discontinuation of propylthiouracil and aggressive treatment, she developed septic shock and multi-organ failure, leading to her death. CONCLUSION: Aplastic anemia has been sparingly reported as an extremely rare complication of propylthiouracil. Further adding to the ambiguity is the unknown etiology and lack of specific therapy for the complication when attributed to propylthiouracil. The disease can carry an extremely poor prognosis if untreated, as proven by our case. Due to the same reasons, we recommend that further investigations be done to elucidate the pathogenesis and assist with treatment of the disease when caused by propylthiouracil.