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Key Features

Essentials of Diagnosis

POLYARTERITIS NODOSA

  • Medium-sized arteries are affected

  • Clinical findings depend on the arteries involved; lungs are spared

  • Common features

    • Fever

    • Abdominal pain

    • Extremity pain

    • Livedo reticularis

    • Mononeuritis multiplex

    • Anemia

    • Elevated acute phase reactants (erythrocyte sedimentation rate [ESR] or C-reactive protein or both)

  • Kidney involvement causes renin-mediated hypertension

  • Associated with hepatitis B (10% of cases)

MICROSCOPIC POLYANGIITIS

  • Necrotizing vasculitis of small- and medium-sized arteries and veins

  • Most common cause of pulmonary-renal syndrome: diffuse alveolar hemorrhage and glomerulonephritis

  • Associated with antineutrophil cytoplasmic antibody (ANCA) in 75% of cases, usually anti-myeloperoxidase antibodies (MPO-ANCA) (that cause a P-ANCA pattern on immunofluorescence testing)

  • ANCA directed against proteinase-3 (PR3-ANCA) (that cause a C-ANCA pattern on immunofluorescence testing) can also be observed

General Considerations

POLYARTERITIS NODOSA

  • A necrotizing arteritis of medium-sized vessels that has a predilection for involving the skin, peripheral nerves, mesenteric vessels (including renal arteries), heart, and brain but spares the lungs

  • Relatively rare, with a prevalence of about 30 cases per 1 million people

  • Approximately 10% of cases are caused by hepatitis B; most cases of hepatitis B–associated disease occur within 6 months of onset of hepatitis B infection

MICROSCOPIC POLYANGIITIS

  • A pauci-immune nongranulomatous necrotizing vasculitis that

    • Affects small blood vessels (capillaries, venules, or arterioles)

    • Often causes glomerulonephritis and pulmonary capillaritis

    • Often is associated with ANCA on immunofluorescence testing (directed against MPO, a constituent of neutrophil granules)

  • Appears in a spectrum overlapping with both polyarteritis nodosa and granulomatosis with polyangiitis (formerly Wegener granulomatosis) because it

    • May involve medium-sized as well as small blood vessels

    • Tends to affect capillaries within the lungs and kidneys

  • Rarely medications induce a systemic vasculitis associated with high titers of p-ANCA and features of microscopic polyangiitis, particularly

    • Propylthiouracil

    • Hydralazine

    • Allopurinol

    • Penicillamine

    • Minocycline

    • Sulfasalazine

Clinical Findings

Symptoms and Signs

POLYARTERITIS NODOSA

  • Fever, malaise, weight loss, and other symptoms develop over weeks to months

  • Pain in the extremities

  • Vasculitic neuropathy

  • Livedo racemosa, subcutaneous nodules, and skin ulcers reflect involvement of deeper, medium-sized blood vessels

  • Digital gangrene is not unusual

  • Lower extremity ulcerations, usually occurring near the malleoli

  • Renin-mediated hypertension due to involvement of renal arteries

  • Acalculous cholecystitis or appendicitis caused by compromised function of major viscera

  • Dramatic presentation in some cases

    • Acute abdomen caused by mesenteric vasculitis and gut perforation

    • Hypotension resulting from rupture of a microaneurysm in the liver, kidney, or bowel

  • Subclinical cardiac involvement is common; overt cardiac dysfunction occurs occasionally

  • Lungs are seldom (if ever) involved

MICROSCOPIC POLYANGIITIS

  • "Palpable" (or "raised") purpura and other signs of cutaneous vasculitis (ulcers, splinter hemorrhages, vesiculobullous lesions)

  • Pulmonary-renal syndromes (eg, anti-glomerular basement membrane disease)

  • Interstitial lung fibrosis that mimics usual interstitial pneumonitis

  • Pulmonary hemorrhage may occur

  • Pathologic ...

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