Systemic Vasculitides
Polyarteritis nodosa (PAN) is a multisystem disorder associated with fibrinoid necrosis of medium-sized arteries. The kidneys are commonly involved at the level of lobular and interlobular arteries, particularly at bifurcations of these vessels. A renal arteriogram demonstrating aneurysms of these vessels is virtually diagnostic of the disorder. Chronic hepatitis B antigenemia is seen in a significant number of patients with PAN.
Mild azotemia and microhematuria, but without hypertension, are seen in over 75 per cent of patients with PAN. Glomeruli show only ischemic changes and sclerosis in these patients. A more dramatic nephritic syndrome, associated with a rapid decline in GFR and frequently associated with accelerated hypertension, occurs in about one third of patients. Fibrinoid necrosis, cellular proliferation, and crescent formation are seen in glomeruli of these patients. Corticosteroids and/or cytotoxic agents can arrest or slow the progression of disease in a significant number of patients.
The course of progressive systemic sclerosis (PSS), or scleroderma, culminates with accelerated hypertension associated with a rapid decrease in renal function in 10 to 20 per cent of cases. The clinical presentation is similar to that of rapidly progressive glomerulonephritis, with the added neuroretinal features of malignant hypertension. The primary renal lesion is that of extensive intimal proliferation in interlobular arteries and fibrinoid necrosis of small arteries and glomeruli. This lesion may be evident in patients who exhibit no clinical signs of renal disease. Treatment is directed toward rigorous control of hypertension, but renal failure is usually inevitable.
Wegener’s granulomatosis is a vasculitis of small arterioles of the respiratory tract and kidneys. The typical clinical presentation includes destructive sinusitis with nodular pulmonary infiltrates and nephritis. The renal lesion is that of a focal, necrotizing glomerulonephritis with extensive cellular proliferation. The diagnosis should be made on the basis of the clinical presentation plus evidence of a granulomatous vasculitis of the respiratory tract. Differentiation from Goodpasture’s syndrome can be made on the basis of the sinus involvement and nodular, as opposed to diffuse, pulmonary radiographic changes in Wegener’s. Renal biopsies are rarely diagnostic because the diagnostic granulomatous lesion is found in vessels not commonly sampled by renal biopsy. Remarkable responses, includinga high rate of total cures, have been seen with aggressive cytotoxic therapy using cyclophosphamide.