Non-Neoplastic Dermatopathology

5.1

E RYTHEMA NODOSUM VS NODULAR VASCULITIS

Erythema Nodosum

Nodular Vasculitis

Age

Any age; most commonly between 25 and 40 years of age; women more often than men. Extensor surfaces of legs and knees; less commonly on thighs, arms, calves, and face. Delayed-type hypersensitivity due to exposure to a variety of antigens. Underlying causes include infection, medications, malignancy, inflammatory bowel disease, and other inflammatory processes. Between 30% and 50% of cases are idiopathic. Abrupt onset of tender, erythematous, nonulcerated, fixed nodules on bilateral shins. May have prodrome of fever, fatigue, and arthralgias. 1. Septal panniculitis with edema and mixed inflammatory infiltrate (Fig. 5.1.1) . 2. Inflammation includes lymphocytes, histiocytes, neutrophils, and eosinophils, especially in early lesions (Figs. 5.1.2 and 5.1.4) . 3. Noncaseating granulomas including Miescher radial granulomas characterized by macrophages surrounding cleft-like spaces with or without clusters of neutrophils (Figs. 5.1.3 and 5.1.5) . 4. Septal fibrosis with mild extension of inflammation into fat lobules (Figs. 5.1.2 and 5.1.3) . 5. No vasculitis. PAS or GMS and AFB stains to exclude fungal and mycobacterial infection. Treatment is not generally necessary but nonsteroidal anti-inflammatory agents and potassium iodide may be used for symptomatic relief. Intralesional or systemic glucocorticoids are alternative therapies for nonresponsive cases. Nodules spontaneously resolve within 2 months but may have postinflammatory hyperpigmentation.

Adults; more common in women than in men.

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 or mixed lobular and septal panniculitis with mixed inflammatory infiltrate consisting of lymphocytes, plasma cells, histiocytes, neutrophils, and eosinophils (Figs. 5.1.6-5.1.8) . 2. Granuloma formation may be present but less frequent than erythema nodosum. 3. Vasculitis involving variably sized arterial and venous vessels with fibrinoid necrosis and leukocytoclasis (Fig. 5.1.9) .

Special studies

Histochemical stains to exclude bacterial, fungal, and mycobacterial infection. Identification and treatment of underlying cause, including therapy for active or latent tuberculosis if present. Nonsteroidal anti-inflammatory medications and rest for symptomatic relief. Oral potassium iodide provides rapid response in most cases. Variable course. Resolution of disease with treatment of underlying cause, but cases associated with tuberculosis may recur. Idiopathic cases may persist for months to years.

Treatment

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Prognosis

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