We report the case of a patient who developed antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) after receiving the coronavirus disease 2019 (COVID-19) vaccine BNT162b (Pfizer–BioNTech). A 37-year-old Japanese woman had been taking propylthiouracil for Graves’ disease. She had erythema on her forearm on the 12th day after receiving the first dose of the vaccine, fever on the 13th day, and redness and swelling of her left auricle on the 25th day. Her serum myeloperoxidase-ANCA and proteinase 3-ANCA levels, which were negative before the Graves’ disease treatment, were elevated. She had unilateral auricular symptoms but no other typical relapsing polychondritis findings. She was diagnosed with propylthiouracil-induced AAV. She was treated with oral glucocorticoids, and her symptoms improved. Propylthiouracil is considered to be the main cause of the onset of AAV in this case, but it cannot be ruled out that BNT162b may have had some effect on the onset of the disease. Although the development of propylthiouracil-induced AAV in this case may have been incidental and unrelated to the vaccination, this report provides important data for evaluating the safety of the vaccine.

Relapsing polychondritis (RP) is a rare autoimmune inflammatory disease characterized by recurrent inflammation and destruction of cartilage. Although auricular chondritis is a characteristic finding in RP, it can be difficult to diagnose in the absence of auricular symptoms. A 64-year-old Japanese male was referred to our hospital with fever and respiratory distress. Contrast-enhanced computed tomography (CT) revealed bronchial wall thickening and we suspected RP; however, he had no auricular symptoms and did not meet the diagnostic McAdam criteria for RP, so we used ¹⁸F-fluorodeoxyglucose positron emission tomography/CT (FDG-PET/CT) to search for other cartilage lesions. This analysis revealed FDG accumulation not only in the bronchial walls, but also in the left auricle. Instead of a bronchial biopsy using a bronchoscope, we performed a biopsy of the left auricular cartilage, which is considered a relatively less invasive site. Even though the auricle was asymptomatic, the pathology results revealed chondritis. He was diagnosed with RP, and his symptoms rapidly improved with corticosteroid therapy. A biopsy of asymptomatic auricular cartilage may be useful in the diagnosis of RP. FDG-PET/CT is a powerful tool for the early diagnosis of RP, identifying inflammatory areas even in the absence of symptoms, and guiding the selection of appropriate biopsy sites.