Cyclic Thrombocytopenia Complicated by Thrombosis and Successfully Treated With Rituximab: A Diagnostic and Therapeutic Challenge.

Cyclic thrombocytopenia (CTP) is a rare hematologic disorder characterized by fluctuating platelet counts and is often misdiagnosed as immune thrombocytopenia. We present the case of a 51-year-old woman with a history of severe thrombocytopenia and mucocutane-ous bleeding since 2012, initially treated as immune thrombocytopenia with corticoster-oids, splenectomy, and azathioprine, without sustained response. Over time, she devel-oped pronounced cyclic fluctuations in platelet counts (<10,000/mm³ to >150,000/mm³) every 21 days. Treatment with eltrombopag resulted in deep venous thrombosis and a major pulmonary bleeding episode associated with anticoagulation. After secondary causes and bone marrow disorders were excluded, cyclic thrombocytopenia was diag-nosed. Rituximab (375 mg/m² weekly for four weeks) led to a significant reduction in platelet oscillations, with no further significant bleeding. This case highlights the diagnos-tic challenges of CTP, underscores the thrombotic risks of thrombopoietin receptor agonists, and supports rituximab as a potential treatment for refractory cases with high thrombo-hemorrhagic risk.