Polyarteritis nodosa (PAN) is an uncommon systemic vasculitis characterized by subacute or chronic, focal, episodic necrotizing inflammation of medium-sized and small muscular arteries. Classic PAN and microscopic polyangiitis (microscopic polyarteritis) are differentiated by the presence or absence of small vessel involvement. The disease presents in patients between the ages of 40 and 60 years and affects men 3 times more frequently than women, with an annual incidence rate of approximately 0.7 per 100,000 individuals. Although there are no racial or geographic predisposing factors, 10% of the patients are positive for hepatitis B surface antigen, implicating hepatitis B as an etiologic agent. Indeed, the demonstration of circulating immune complexes composed of hepatitis B antigen and antibodies to hepatitis B in vessel walls during the early stages of the disease strongly implicate immune-complex–mediated mechanisms in the pathogenesis of PAN.
Constitutional symptoms, including fatigue, fever, weight loss, and arthralgia, are seen in up to 75% of patients, with mononeuritis multiplex being the most common symptom, if not the initial presenting sign. Renal involvement, related to vasculitis, is common, as is secondary hypertension, which affects approximately one-third of patients. Gastrointestinal disease with small bowel ischemia and infarction occurs less frequently but may lead to serious complications. Other systemic manifestations include cutaneous involvement (eg, subcutaneous nodules), purpura or Raynaud phenomenon, coronary arteritis, pericarditis, and hematologic abnormalities. CNS disease associated with PAN is rare.
Ocular involvement is present in up to 20% of patients with PAN, arising as a consequence of the underlying vascular disease. In the posterior pole, this may manifest as hypertensive retinopathy replete with macular star formation, cotton-wool spots, and intraretinal hemorrhage in patients with renal disease; retinal arteriolar occlusive disease; or choroidal infarcts with exudative retinal detachment secondary to vasculitis involving the posterior ciliary arteries and choroidal vessels (Fig 6-21). Elschnig spots may be observed in the posterior pole as a result of choroidal ischemia. Neuro-ophthalmic manifestations include cranial nerve palsies, amaurosis fugax, homonymous hemianopia, Horner syndrome, and optic atrophy. Scleral inflammatory disease of all types, including necrotizing and posterior scleritis, has been reported. Peripheral ulcerative keratitis (PUK), typically accompanied by scleritis, may be the presenting manifestation of PAN.
The diagnosis of PAN is made by fulfilling 3 of the 10 classification criteria:
weight loss of more than 4 kg
testicular pain or tenderness
myalgia, weakness, or leg tenderness
mononeuropathy or polyneuropathy
elevated diastolic blood pressure (≥90 mm Hg)
elevated blood urea nitrogen
positive hepatitis B serology
abnormal arteriographic findings
demonstration of neutrophils on biopsy specimens of small or medium-sized arteries
The presence of antineutrophil cytoplasmic antibody (ANCA) further suggests the diagnosis (see the discussion of Wegener granulomatosis in the following section). The 5-year mortality rate of untreated PAN is 90%. Although systemic corticosteroid use may reduce this rate to 50%, appropriate treatment mandates combination therapy with immunomodulatory medications such as cyclophosphamide, which improves 5-year survival to 80% and may induce long-term remission of the disease. It is therefore important to consider PAN in the differential diagnosis of retinal vasculitis presenting in patients with multiple systemic complaints in whom an underlying necrotizing vasculitis is suspected; appropriate diagnosis and management can be life-saving. Tissue biopsy confirms the diagnosis.
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