Abstract
BACKGROUND Immunotherapy is a novel treatment offering an alternative to traditional chemotherapeutic agents for different malignancies. Hematologic adverse reactions (HARs) related to immune checkpoint inhibitors (ICIs) are uncommon. Pure red cell aplasia (PRCA) is a rare hematologic complication of ICI therapy in metastatic melanoma with significant mortality risk despite treatment with steroids or immunosuppressive therapy. For unexplained acute anemia after exclusion of other causes, performing bone marrow biopsy is imperative to diagnose PRCA and rule out involvement of bone marrow by primary tumor. HARs can occur during ICI therapy or even after ICI therapy is stopped. ICI rechallenge, even after the development of HARs, is considered in some patients with good response to treatment of HARs from ICIs. Recurrence of HARs with the same or different type of reaction is seen in some patients. CASE REPORT Two cases of ICI-induced PRCA were confirmed on bone marrow biopsy after dual ICI treatment with nivolumab and ipilimumab in metastatic melanoma. In case 2, PRCA was successfully treated with steroids and later rechallenged with single-agent nivolumab, causing mild ICI-induced immune thrombocytopenia, which did not require treatment with steroids. CONCLUSIONS It is crucial to increase clinician awareness of the possibility of PRCA development not only during treatment with ICI but also after finishing treatment with ICI; there is high mortality associated with missing an opportunity to diagnose and treat PRCA on time with favorable results. ICI rechallenge can be considered in patients who showed response to immunotherapy, especially those with limited alternative therapeutic options.