Corticosteroid-Resistant Secondary Immune Thrombocytopenia in Smoldering Multiple Myeloma Successfully Treated With Eltrombopag: A Case Report.

Immune thrombocytopenia (ITP) is an uncommon yet clinically significant cause of thrombocytopenia in multiple myeloma (MM). We report a case of an 80-year-old female with severe thrombocytopenia identified during routine follow-up after breast cancer surgery, leading to the simultaneous diagnosis of Smoldering multiple myeloma (sMM) and secondary ITP. Laboratory findings, including an elevated immature platelet fraction, increased platelet-associated immunoglobulin G (IgG), and preserved megakaryopoiesis, supported a diagnosis of immune-mediated platelet destruction. The patient demonstrated only a transient response to corticosteroids but achieved sustained remission with eltrombopag (EPAG), while maintaining stable M-protein levels and showing no myeloma-defining events (MDEs). This report highlights the importance of considering secondary ITP in the evaluation of patients with MM.