Severe Immune Thrombocytopenic Purpura Following Influenza Vaccination: A Case Report

Immune thrombocytopenia (ITP) is a rare, acquired bleeding disorder caused by various underlying etiologies. ITP can be triggered by medication, infections, cancers, and autoimmune diseases. One of the rare triggers is vaccination. As in many cases, the symptoms are mild and the cause is idiopathic, and it may not be diagnosed without extensive investigations. It can also be difficult to differentiate between medication-induced thrombocytopenia and ITP, particularly in older patients with multiple comorbidities and receiving multiple medications. Here, we describe an older patient with acute onset ITP following influenza vaccination. An 88-year-old man presented with complaints of systemic itchiness and bleeding from his mouth. Four days prior to the symptoms appearing, he had received an influenza vaccine and did not experience any severe pain or anaphylactic symptoms. On presentation, he had multiple bleeding blisters and systemic petechiae. Blood tests revealed a platelet count of 1000/µL. A month prior, his platelet count was 1.5×10⁵/µL. The blood culture results were negative and a bone marrow biopsy revealed multiple megakaryocytes, without blastocytes or evidence of hemophagocytosis. The patient was diagnosed with influenza vaccine-induced severe ITP and was treated with intravenous high-dose prednisolone. Although vaccine-related ITP is rare, in patients with systemic symptoms, primary care physicians should perform systematic physical examinations to detect any hemorrhage, as ITP is a possibility.