General Principles

• IgA nephropathy is a result of abnormal glycosylation of the hinge region of immunoglobulin A. This results in autoantibodies which interact with abnormally glycosylated protein and cause glomerular disease. Although serum IgA levels do not correlate with disease activity, events that potentially lead to overproduction (concurrent upper respiratory infection) or decreased clearance (hepatic cirrhosis) may predispose to development of this disease.
• This disease process is typically idiopathic, characterized by a nephritic picture with microscopic (and less commonly, macroscopic) hematuria and nonnephrotic range proteinuria.
• Presentation is usually in the second or third decade of life, often following a slowly progressive course. Multiple forms of pathology exist, from mild lesions and mesangial proliferation to global sclerosis resulting in progression to ESRD.
• Henoch–Schönlein purpura is a related disorder that may represent a systemic form of the disease, with vasculitis of the skin (palpable purpura of the lower trunk and extremities), gastrointestinal tract, and joints.