Non-Neoplastic Dermatopathology

5.12 N ODULAR VASCULITIS VS POLYARTERITIS NODOSA

Nodular Vasculitis

Polyarteritis Nodosa

Age

Adults; more common in women than men.

All ages, but most common in middle-aged to older adults. Most commonly involves the lower extremities with less frequent involvement of the upper extremities, trunk, and head and neck regions. Immune complex–mediated vasculitis hypothesized to be due to development of anti-phosphatidylserine-prothrombin complex antibodies and activation of classical complement pathway. Underlying inflammatory bowel disease, infection, malignancy, and medication use have been associated with cutaneous polyarteritis nodosa. Initially presents with livedo reticularis and tender subcutaneous nodules. These may progress to purpura, necrosis, and ulceration of the skin. May experience digital infarction in severe cases. Extracutaneous manifestations include malaise, weight loss, fever, myalgias, arthralgias, and neuropathy. 1. Intact epidermis is relatively normal. Ulceration may be present in older lesions. 2. Transmural infiltration of the walls of medium-sized vessels of the deep reticular dermis and subcutis by infiltrate predominated by neutrophils (Fig. 5.12.5) . No granuloma formation. 3. Fibrinoid degeneration of the vessel walls with inflammation surrounding affected vessel (Fig. 5.12.6) . Intraluminal thrombus may be present. 4. No significant involvement of the fat lobules.

Location

Posterior lower legs/calves.

Etiology

Immune-mediated hypersensitivity reaction most frequently associated with tuberculosis. Other infections, inflammatory processes, and medications less commonly associated. Minority of idiopathic cases.

Presentation

Unilateral or bilateral, tender, erythematous nodules that typically ulcerate.

Histology

1. Lobular panniculitis with mixed inflammatory infiltrate consisting of lymphocytes, plasma cells, histiocytes, neutrophils, and eosinophils (Figs. 5.12.1 and 5.12.2) . 2. Granuloma formation may be present. 3. Vasculitis involving variably sized arterial and venous vessels with fibrinoid necrosis and leukocytoclasis (Fig. 5.12.3) . Vasculitis not limited to medium-sized vessels. 4. Lipophagic fat necrosis with formation of microcysts (Fig. 5.12.4) .

Histochemical stains to exclude bacterial, fungal, and mycobacterial infection. Direct immunofluorescence is relatively nonspecific but may show deposition of C3 and IgM around medium-sized vessels. May have mild anemia, leukocytosis, and elevated erythrocyte sedimentation rate. Serologies to exclude other forms of vasculitis involving medium-sized vessels may be indicated; not associated with anti-neutrophil cytoplasmic antibodies. Copyright © Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited. 2023

Special studies

278