Propylthiouracil: A Well Known Cause of Agranulocytosis, but Can It Cause Aplastic Anemia?

Abstract

Background: Propylthiouracil (PTU) 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 generally unheard of. Our case will be the third in literature to suggest aplastic anemia as a side effect of PTU, 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 PTU to control the thyroid activity. Soon after that, she was admitted with severe neutropenia, which progressed to aplastic anemia. Despite discontinuation of PTU 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 PTU. It has not been investigated further due to the sparse events and therefore insufficient data. Further adding to the ambiguity is the unknown etiology and lack of specific therapy for the complication when attributed to PTU. The disease can carry a poor prognosis if untreated, as proven by our case, and the use of PTU being relatively commonplace, it is crucial that the complication be considered and aggressively treated. Due to the same reasons, we recommend that further investigations be done to elucidate the pathogenesis and assist with treatment of the disease when found in respect to PTU.