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| Fig. 29.6 Erythema nodosum leprosum. The reactive state in lepromatous leprosy resembles erythema nodosum but may be bullous, as seen in this patient. |
There are two types of reactions that may occur spontaneously but often follow the initiation of antibacterial therapy by months to years. Approximately half of all leprosy patients experience one of these acute inflammatory episodes at some point in their disease course.
Type I reactions (reversal reactions) complicate unstable dimorphous leprosy and represent alterations in the patient’s cell-mediated immunity. The immunity may be either upgraded or downgraded. Typically, in type I reactions, existing lesions become acutely inflamed.
Type II reactions (most commonly erythema nodosum leprosum [ENL]) occur in lepromatous leprosy (Fig. 29-6). ENL reactions are believed to represent immune complex precipitation in blood vessels due to released antigens from
M. leprae organisms that have been damaged by antibiotic therapy. The patients develop red, tender nodules mainly on their extremities, associated with constitutional symptoms including fever, arthralgias, lymphadenitis, and neuritis.
Burdick AE: Leprosy including reactions. In Lebwohl M, Heymann WR, Berth-Johnes J, Coulson I, editors:
Treatment of skin disease, New York, 2002, Mosby, pp 336–339.
