Non-Neoplastic Dermatopathology

5.2

E RYTHEMA NODOSUM VS BEHCET DISEASE

Erythema Nodosum

Behcet Disease

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 (Figs. 5.2.1 and 5.2.2) . 2. Inflammation includes lymphocytes, histiocytes, neutrophils, and eosinophils, especially in early lesions (Figs. 5.2.2 and 5.2.3) . 3. Noncaseating granulomas including Miescher radial granulomas characterized by macrophages surrounding cleft-like spaces with or without clusters of neutrophils (Fig. 5.2.4) . 4. Septal fibrosis with slight extension of inflammation into fat lobules (Figs. 5.2.1 and 5.2.2) . 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.

Young adults between 20 and 40 years of age.

Location

Extremities, predominantly anterior legs.

Etiology

Exact cause is unknown. Agents, including infectious organisms or environmental factors, trigger aberrant immune activity in genetically susceptible individuals. Formation of immune complexes and autoantibodies, in the presence of vascular endothelial and neutrophil activation, leads to vasculitis. The erythema nodosum–like lesions present as discrete, erythematous nodules with edema. Other associated clinical features include aphthous ulcers and uveitis. 1. Primarily lobular or mixed septal and lobular panniculitis with neutrophil predominant infiltrate (Figs. 5.2.5 and 5.2.6) . 2. Lymphocytic and neutrophilic inflammation of medium-sized vessels with thrombus formation and erythrocyte extravasation (Fig. 5.2.8) . 3. Lymphocytes and histiocytes extend into lobules and are associated with fat necrosis (Fig. 5.2.7) .

Presentation

Histology

Special studies

No specific laboratory tests. May have elevated erythrocyte sedimentation rate and C-reactive protein with active disease. Topical corticosteroids for mild cases. Prednisone, azathioprine, colchicine, dapsone, thalidomide, or methotrexate for severe or refractory disease.

Treatment

Chronic disease with waxing and waning course. Involvement of other organ systems may be associated with significant morbidity and mortality. Copyright © Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited. 2023

Prognosis

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