Thrombocytopenia and pneumonitis associated with BNT16B2b2 mRNA COVID-19 vaccine: A case report

•In this case, pneumonia occurred concurrently with thrombocytopenia.•This was suspected to be related to the BNT16B2b2 mRNA vaccine for COVID-19.•We also summarize previous reports of such similar cases.•Patients with immunologic issues need careful management post SARS-CoV-2 vaccination. An 80-year-old Japanese male patient with Behçet’s disease presented with a seven-day history of fever, cough, and progressive shortness of breath after receiving a second dose of the BNT16B2b2 mRNA COVID-19 vaccine (Pfizer-BioNTech). The initial diagnosis was community-acquired pneumonia, and antibiotic treatment was started but proved ineffective. Twenty days after onset, his platelet count was significantly decreased. We suspected vaccine-induced pneumonitis and thrombocytopenia. After administration of prednisolone and intravenous immunoglobulin, and platelet transfusions, his platelet count normalized. The pneumonia symptoms improved three weeks after onset. Herein, we also summarize previous reports of cases of pneumonitis and thrombocytopenia associated with SARS-CoV-2 vaccination.