Article Contributors: 
    Sean Klepper M.D.
    Stephen Lyle, M.D., ...

    Also known as: Hansen's disease

    Clinical Features:

    • Caused by Mycobacterium leprae
    • Rare in the United States, although some cases are seen sporadically in Louisiana and Texas secondary to exposure to armadilloes
    • Divided into several clinical forms: lepromatous, tuberculoid, borderline and indeterminate.  Which form the disease takes in a particular patient is determined by the patient's immune status.  This discussion will focus on tuberculoid leprosy, since it is the form that shows tuberculoid granulomas.
    • The tuberculoid form of leprosy affects patients who are capable of mounting an effective cellular immune response against the organism.  It presents with one to a few hypoesthetic, often scaly, annular patches or plaques, which are often hypopigmented, and frequently also with palpable peripheral nerves.

    Histologic Features:

    • Tuberculoid granulomas (defined as granulomas surrounded by a rim of lymphocytes)
    • The granulomas may be linear, following the course of a peripheral nerve.
    • No grenz zone, in contrast to lepromatous leprosy
    • Few to no acid-fast bacteria on Fite stain (preferred to Ziehl-Neelson for M. leprae), as opposed to lepromatous leprosy, in which they are numerous.  Immunohistochemical staining for AFB may be more fruitful in some cases.
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