Sunitinib Induced Thrombotic Thrombocytopenic Purpura in addition to Severe Hypothyroidism: A Case Report and Review of the Literature.

Introduction. Sunitinib malate is an oral multitargeting tyrosine kinase inhibitor approved for the first line treatment of metastatic renal cell carcinoma. Sunitinib administration is associated with several adverse events including fatigue, diarrhea, skin toxicity, hypothyroidism, and cytopenia. Herein, we present a case of thrombotic thrombocytopenic purpura and clinical hypothyroidism presenting within 4 weeks of starting sunitinib therapy. Case Presentation. A 72-year-old woman with metastatic renal cell carcinoma presented with generalized fatigue 28 days after starting sunitinib 50 mg daily. She was found to have severe hypothyroidism, in addition to significant thrombocytopenia and anemia. The latter were explained by a clinical and laboratory diagnosis of thrombotic thrombocytopenic purpura. Sunitinib was stopped and she recovered completely after plasmapheresis. Conclusion. To our knowledge, this is the fourth case report of thrombotic thrombocytopenic purpura secondary to sunitinib. Oncologists should be aware of this rare but potentially fatal adverse event. We highly suggest to routinely test for platelet count and thyroid stimulating hormone level as early as two weeks after initiating sunitinib.