Surgical Pathology of Diffuse Parenchymal Lung Disease in Adults With IgA Vasculitis or IgA Nephropathy

IgA vasculitis (IgAV) and IgA nephropathy (IgAN) are closely related disorders that usually present in childhood. Pulmonary involvement is rare and histopathologic features thereof in adults are poorly understood. Institutional archives were searched for adults with IgAV or IgAN and diffuse parenchymal lung disease. Ten patients (6 men, median age 59 years) with lung tissue sampling were enrolled. Clinical history and pathology slides were reviewed. All patients were diagnosed with IgAV or IgAN before or concurrently with lung disease. Symptoms were nonspecific but hemoptysis was common. Radiologically, bilateral ground-glass opacities, consolidation, and reticulonodular densities were typical. Histologically, 6 cases (60%) featured acute or subacute diffuse alveolar hemorrhage (DAH) accompanied by definite (40%) or probable (20%) capillaritis. Two cases (20%) featured resolved DAH only, manifesting as alveolar hemosiderosis without other changes. And 2 cases featured organizing pneumonia without DAH. Five patients had a chronic interstitial pneumonia in the background, including 3 with nonspecific interstitial pneumonia (NSIP) and 2 with unclassifiable fibrosis. Findings were similar in IgAV versus IgAN. Of 4 patients with follow-up information, 2 died during hospitalization, one died 9 weeks later of secondary complications, and one was treated with rituximab and nintedanib and is alive 2 years later. To our knowledge, this is the largest series detailing pulmonary histopathologic findings in adults with IgAV or IgAN. Most cases show acute DAH with capillaritis; less commonly, old DAH, organizing pneumonia, NSIP, or unclassifiable fibrosis may be observed. Some patients do well with treatment but fatal cases also occur.