Granulomatous polyangiitis misdiagnosed as hematogenous lung abscess: A case report.

Granuloma polyangiitis (GPA) is a necrotizing granulomatous inflammation, which is a systemic autoimmune disease that mainly affects the upper respiratory tract, lungs, and kidneys. Clinically, the clinical manifestations of GPA vary greatly, and it is extremely easy to be misdiagnosed. We report a 60-year-old man with granulomatous polyangiitis with dysuria and parotid gland enlargement as the first symptom. As the condition worsened, he gradually developed symptoms in multiple systems such as persistent high fever, nosebleeds, hemoptysis, skin rash, and multiple cavities in the lungs. Due to high fever, hemoptysis, and the gradual expansion of lung cavities, the suspected hematogenous lung abscess was not well controlled and transferred to the respiratory department. The manifestation of involvement was finally confirmed by skin biopsy. Biopsy was performed on the skin of the lower extremities with a dark red rash with multiple microprojections. Pathology indicated neutrophilic infiltration and necrosis of small vessel walls, and granuloma formation. Blood anti-protease 3 antibody (PR3) was positive Monotherapy with prednisone. Body temperature gradually returned to normal; hemoptysis and nasal bleeding disappeared; parotid gland enlargement and dysuria relieved, and lung cavities gradually reduced. When anti-infective treatment is ineffective, we should consider the presence of some non-infectious diseases, especially when multiple systems are involved; biopsy should be performed as soon as possible. Granulomatous polyangiitis has various manifestations. Parotid glands and prostate may also be the first organs involved, not limited to common targets such as the respiratory tract and kidneys.