A case of antineutrophil cytoplasmic antibody-associated vasculitis and sclerosing mediastinitis.

Sclerosing mediastinitis (SM) is a rare condition characterised by extensive fibrous proliferation within the mediastinum. While some patients remain asymptomatic, others may present with chest pain, dyspnoea, haemoptysis, or complications such as superior vena cava syndrome or pulmonary hypertension. The aetiology of SM may be caused by infections, malignancies, autoimmune diseases, radiation therapy, or have idiopathic origins. We present a case of a 55-year-old man diagnosed with SM and granulomatosis with polyangiitis. The patient initially presented from an outside hospital with a large periaortic soft tissue mass, accompanied by symptoms of cough, shortness of breath, haemoptysis, and joint pain. Laboratory findings revealed elevated inflammatory markers and positive antineutrophil cytoplasmic antibody targeting proteinase-3. Imaging studies demonstrated abnormal mediastinal soft tissue encasing the thoracic aorta with subcarinal lymphadenopathy. Biopsy of the mass confirmed fibrotic tissue consistent with SM, and kidney biopsy revealed crescentic glomerulonephritis indicative of granulomatosis with polyangiitis. Treatment involved high-dose corticosteroids and rituximab, leading to significant improvement in overall patient status. The patient's follow-up revealed sustained remission, with resolution of lung infiltrates and decreased mediastinal mass size. Although the association between SM and antineutrophil cytoplasmic antibody-associated vasculitis remains unclear, our case highlights the importance of considering both diagnoses in a presentation of mediastinal fibrosis. Further research is warranted to clarify optimal management strategies for these rare conditions.