Leprosy usually involves the skin and peripheral nerves, and the clinical features depend on the body's immune response to the organism Mycobacterium leprae.
Indeterminate leprosy is the commonest clinical type, especially in children. This presents as hypopigmented or erythematous circular macules with occasional mild anesthesia and scaling. This may resolve spontaneously or progress to one of the other types. Biopsy reveals a perineural granulomatous infiltrate and scant acid-fast bacilli.
Tuberculoid leprosy presents with a few hypopigmented or erythematous plaques with an active erythematous, raised rim. Lesions are usually markedly anesthetic, dry and hairless reflecting the nerve damage. Nerves may be enlarged and palpable. Biopsy shows a granulomatous infiltrate centered on nerves, but no organisms.
Lepromatous leprosy presents with multiple inflammatory papules, plaques and nodules. Loss of the eyebrows ('madarosis') and nasal stuffiness are common. Skin thickening and severe disfigurement may follow. Anesthesia is much less prominent. Biopsy shows numerous acid-fast bacilli.
The diagnosis of leprosy is essentially clinical with:
Recommended treatment regimens for leprosy in adults (modified WHO guidelines)
Multibacillary leprosy (LL, BL, BB)
Treatment continued for 12 months
Paucibacillary leprosy (BT, TT)
Treatment continued for 6 months.