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ESSENTIALS OF DIAGNOSIS

  • Subacute onset of constitutional complaints (fever, weight loss, malaise, arthralgias), lower extremity nodules and ulcerations, mononeuritis multiplex, and postprandial pain are hallmarks of polyarteritis nodosa (PAN).

  • Cutaneous PAN is a variant of the systemic disease in which vasculitis is limited to the skin and often presents with painful nodules, livedo racemosa, or cutaneous ulcerations.

  • Patients with PAN should be evaluated for hepatitis B, though hepatitis B virus-associated PAN has decreased in incidence and is now only responsible for less than 10% of cases.

  • Angiography may reveal microaneurysms in the kidneys or gastrointestinal tract.

  • Biopsies of the skin and peripheral nerves (with sampling of the adjacent muscle) are the least invasive ways of confirming the diagnosis histopathologically.

General Considerations

Classic polyarteritis nodosa (PAN) is characterized by necrotizing inflammation of muscular arterioles and medium-sized arteries that spares the smallest blood vessels (ie, capillaries). PAN is not associated with glomerulonephritis, although it can cause renovascular hypertension and renal infarctions through its involvement of the medium-sized intrarenal vasculature. Features that distinguish PAN from other forms of systemic vasculitis are confinement of the disease to the arterial as opposed to the venous circulation, the sparing of the lung, the absence of granulomatous inflammation, and the lack of any association with a known autoantibody.

Reported annual incidence rates of PAN range from two to nine cases per million people per year. A higher incidence (77 cases/million) was reported in an Alaskan area hyperendemic for hepatitis B virus (HBV). With the availability of the HBV vaccine, however, the percentage of cases associated with HBV has declined substantially (from previously over one-third of cases to now <10% of all cases in the developed world). PAN appears to affect men and women with approximately equal frequencies and to occur in all ethnic groups.

CLINICAL FINDINGS

A. Symptoms and Signs

PAN can involve virtually any organ system with the exception of the lungs. The disease demonstrates a predilection for certain organs, particularly the skin, peripheral nerves, gastrointestinal tract, and kidneys. Pain is often a nearly universal complaint among patients and can be caused by myalgias, arthritis, peripheral nerve infarction, testicular ischemia, or mesenteric vasculitis. A summary of the signs and symptoms seem in PAN is shown in Table 31–1.

Table 31–1.Clinical findings in polyarteritis nodosa.

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