Leprosy is a chronic indolent mycobacterial infection mainly of the skin.
Rare since WHO eradication programmes.
Leprosy is found primarily in Africa and Asia.
Leprosy is caused by an intracellular acid-fast bacillus, Mycobacterium leprae. The mode of transmission is un-certain and the incubation may be many years.
Five patterns of disease are recognised that are dependent on the immunological response of the individual (see Table 9.8).
There are two immunological reactions that may occur in borderline or lepromatous leprosy.
Reversal reaction (lepra type I) is seen following treatment of borderline leprosy. It is a type IV hyper-sensitivity reaction resulting in acute inflammation characterised by erythema and oedema of skin lesions, accompanied by neuritis.
Erythema nodosum leprosum (lepra type II) is a type III hypersensitivity reaction seen in boderline and lepromatous leprosy. It is characterised by fever and multiple erythematous tender nodules.
The diagnosis is clinical but can be confirmed with demonstration of acid-fast bacilli in skin scrapings. PCR can be used.
Patients are treated with dapsone and rifampicin. Clofazimine is added in BB, BL and LL types. Patients may require surgery and physiotherapy for deformities. Reversal reaction is treated with prednisolone. Erythema nodosum leprosum is treated with analgesia, chloroquine, clofazimine and antipyretics (thalidomide has also been used).