Leprosy is a granulomatous disease primarily affecting the peripheral nerves and skin. It is caused by Mycobacterium leprae.

Features

• patches of hypopigmented skin typically affecting the buttocks, face, and extensor surfaces of limbs
• sensory loss

The degree of cell mediated immunity determines the type of leprosy a patient will develop.

Low degree of cell mediated immunity → disseminated lepromatous leprosy ('multibacillary')

• extensive skin involvement
• symmetrical nerve involvement
  • Nerve thickening may be felt on palpation, with the most commonly affected nerves being the ulnar, median, radial cutaneous, greater auricular, common peroneal and posterior tibial nerves.

High degree of cell mediated immunity → tuberculoid leprosy ('paucibacillary')

• limited skin disease
• asymmetric nerve involvement → hypesthesia
• hair loss

Investigations

Biopsies/smears - acid fast bacilli

Diagnosis