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Leprosy : Type 1 Lepra Reaction

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Lepra reactions are immune-mediated episodes of acute or subacute inflammation seen during the course of leprosy. They occur in up to 25% of patients with paucibacillary leprosy and up to 40% of patients with multibacillary leprosy.

Type 1 lepra reactions are delayed hypersensitivity response to M. leprae antigens where as Type 2 lepra reactions are mediated via antibody response to M. lepra antigens and are associated with immune complex deposition in various tissues.

Type 1 lepra reactions are delayed hypersensitivity reactions to M. leprae antigens and occur most frequently in borderline leprosy patients after the onset of therapy. They reflect strengthening of cellular immune response against M. leprae towards tuberculoid type. Mild reactions are characterized by erythema and induration of existing skin lesions. There is no nerve impairment and there are no systemic symptoms. Severe type 1 lepra reactions show nerve involvement which can rapidly lead to muscle weakness, loss of sensation, paralysis, and deformity if not treated promptly.

Treatment: Mild reactions are treated with analgesics. If there is evidence of neuritis, corticosteroids are administered.

Case History: The image shows skin lesions of type 1 lepra reaction in a 60 y/o female with multibacillary leprosy. She developed the reaction early during the course of multidrug therapy. Image courtesy of: Shahbaz Janjua, MD; Global Skin Atlas; Used with permission.

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