Skip directly to search Skip directly to A to Z list Skip directly to navigation Skip directly to page options Skip directly to site content

Hansen's Disease / Leprosy (Mycobacterium leprae)
1997 Case Definition

Clinical Description

A chronic bacterial disease characterized by the involvement primarily of skin as well as peripheral nerves and the mucosa of the upper airway. Clinical forms of Hansen's disease represent a spectrum reflecting the cellular immune response to Mycobacterium leprae. The following characteristics are typical of the major forms of the disease:

  • Tuberculoid: one or a few well-demarcated, hypopigmented, and anesthetic skin lesions, frequently with active, spreading edges and a clearing center; peripheral nerve swelling or thickening also may occur
  • Lepromatous: a number of erythematous papules and nodules or an infiltration of the face, hands, and feet with lesions in a bilateral and symmetrical distribution that progress to thickening of the skin
  • Borderline (dimorphous): skin lesions characteristic of both the tuberculoid and lepromatous forms
  • Indeterminate: early lesions, usually hypopigmented macules, without developed tuberculoid or lepromatous features

Laboratory Criteria for Diagnosis

Demonstration of acid-fast bacilli in skin or dermal nerve, obtained from the full-thickness skin biopsy of a lepromatous lesion

Case Classification


A clinically compatible case that is laboratory confirmed


The 1997 case definition appearing on this page was previously published in the 1990 MMWR Recommendations and Reports titled Case Definitions for Public Health Surveillance. Thus, the 1990 and 1997 versions of the case definition are identical.