What is a type 1 reaction in leprosy?

Updated: Jun 05, 2020
  • Author: Darvin Scott Smith, MD, MSc, DTM&H; Chief Editor: Michael Stuart Bronze, MD  more...
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Reversal reaction, or lepra type 1 reaction, is a delayed-type hypersensitivity reaction that arises when borderline leprosy shifts toward borderline lepromatous leprosy with treatment. These types of reactions reflect the development of an appropriate immune response and the local generation of tumor necrosis factor-alpha and interferon-gamma. The reaction is characterized by edema and erythema of existing skin lesions, formation of new skin lesions, neuritis, and additional sensory and motor loss.

The likelihood of a type 1 reaction in patients with borderline leprosy is 30%. [17]

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