Granulomatosis with polyangiitis associated with IgA nephropathy.

Granulomatosis with polyangiitis (GPA), previously referred to as Wegener's granulomatosis, is a rare necrotizing granulomatous vasculitis, especially in children. GPA affects small- to medium-sized vessels, leading to involvement of multiple organs, including the upper and lower respiratory tracts and kidneys. Glomerular lesions associated with GPA typically present as crescentic glomerulonephritis with necrotizing lesions, with little or no staining for immunoglobulins and complement proteins. We report a unique pediatric case of GPA associated with IgA nephropathy, a representative immune-mediated glomerular disease. The initial renal biopsy specimen revealed fibrous sclerosis and mild mesangial proliferation without deposition of IgA. However, after clinical remission of GPA by treatment, the serum IgA level continued to be significantly higher than normal, and her paranasal sinusitis was poorly controlled. An acute upper respiratory infection resulted in worsened urinary findings without any systemic signs of GPA. The second renal biopsy specimen revealed deposition of IgA and C3 in the mesangium. The patient was treated with oral prednisolone alone, which led to complete remission of proteinuria within 1 month. IgA nephropathy is possibly associated with GPA during remission stage, and serum IgA level may be a valuable indicator to predict its association.