Case Definition

Confirmed Case

Clinical evidence of illness¹ with laboratory confirmation of infection:

• positive acid fast stain with typical morphology for Mycobacterium leprae;

OR

• histopathological report from skin or nerve biopsy compatible with leprosy.
  

Probable Case

• Clinical illness¹ in a person who is epidemiologically linked to a confirmed case.

 Notes:

1. Clinical illness is 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 M. 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 centre; 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.