Necrotic steroid-dependent erythema nodosum leprosum mimicking vasculitis in multibacillary leprosy with negative bacilloscopy: a diagnostic challenge.

Necrotic erythema nodosum leprosum (ENL) is a rare, severe and atypical variant of type 2 reaction characterized skin lesions mimicking vasculitis. Bacilloscopy and histopathological features may not be suggestive, in patients with repeated cycles of multidrug therapy (MDT) and concomitant use of corticosteroids. A 20-year-old man previously diagnosed with multibacillary leprosy received repeated cycles of MDT, at which time he developed recurrent painful nodules that worsened to widespread necrotic ulcers. Although previous bacilloscopy was positive, repeated test during severe ulcerative presentation was negative. Skin biopsy showed extensive ulceration, lobular panniculitis, and medium-vessel vasculitis without granuloma formation. Acid-fast bacilli were not detected on Ziehl-Neelsen staining. Recurrent episodes of flaring were experienced every time the corticosteroid dose was tapered. Necrotic steroid-dependent ENL was diagnosed based on clinicopathological correlation. High-dose corticosteroid therapy was then given, which resulted in complete remission and hypertrophic scarring. No recurrence was experienced during follow-up. Negative bacilloscopy and uncharacteristic histological findings do not exclude necrotic ENL as a differential diagnosis in patients with vasculitic ulceronecrotic lesions.