A fatal case of Immune thrombocytopenia secondary to the immune checkpoint inhibitor ipilimumab in a patient with BRAF wild type metastatic melanoma.

ABSTRACT

INTRODUCTION: Immune checkpoint inhibitors have revolutionized the field of oncology in recent years. Ipilimumab is a monoclonal antibody that targets the protein cytotoxic T-lymphocyte 4, which is involved in the inhibition of cytotoxic T-lymphocytes. When uninhibited, cytotoxic T-lymphocytes can act to recognize and kill cancer cells. This increased activity of immune cells can inadvertently destroy healthy tissue leading to a class of side effects known as immune-related adverse events. Immune thrombocytopenia purpura secondary to checkpoint inhibitors is an uncommon complication (<1%) and in most instances resolve spontaneously without aggressive treatment. CASE REPORT We present a case of immune thrombocytopenia purpura developing in a patient recently started on ipilimumab for BRAF wild-type metastatic melanoma. The patient presented to his primary oncologist with confusion and lethargy. Subsequent blood work revealed a platelet count of 16,000 ng/mL. The patient was transferred to the emergency department where a computed tomography scan revealed bilateral frontal lobe hemorrhages. The patient was admitted to the intensive care unit for further management. MANAGEMENT AND OUTCOME: The patient received IV immunoglobulins at 1 g/kg every 24 h in addition to IV Decadron 40 mg daily. In addition, the patient continued to receive significant platelet transfusions. The patient's platelet count recovered to 78,000 ng/mL (baseline for this patient > 130,000 ng/mL.) The patient developed worsening mental status and was found to have significant increase in previously found bilateral frontal hemorrhages. The patient was transitioned to comfort measures only due to very poor prognosis and passed away in hospice care. DISCUSSION: Checkpoint inhibitors have provided durable responses in multiple cancers that previously had a paucity of treatment options. This case demonstrates that immune thrombocytopenia purpura is a possible adverse event of these therapies and thus platelet monitoring should be included in all patients.