17th June 2024

Leprosy

Leprosy is caused by Mycobacterium leprae and has an almost worldwide distribution, with an incidence of over 100,000 cases per year. It is primarily a disease that affects the skin and peripheral nerves and is contracted through prolonged contact with an untreated individual. Blindness is a potential consequence of the disease.

Diagnosis of leprosy can be made clinically, with findings of stereotypical skin lesions and thickened peripheral nerves. A clinical spectrum exists between paucibacillary leprosy (tuberculoid) and multibacillary leprosy (lepromatous). Multibacillary leprosy is a failure of the cell-mediated immune response to the mycobacteria. This results in more lesions, more affected nerves, and more mycobacteria on skin snippings. Individuals with paucibacillary leprosy will have full anaesthesia over a fewer number of skin lesions, which will be asymmetrically distributed. Bacterial load can be calculated by microscopy of skin scrapings. Treatment regimens are based on whether the clinical picture is one of multibacillary or paucibacillary leprosy. Rifampicin, dapsone and clofazimine are used in combination for multibacillary leprosy, whereas a shorter course of rifampicin and dapsone alone is sufficient to treat paucibacillary leprosy. Steroids are used if new nerve damage is present on routine follow-up or if there is evidence of hypersensitivity or immune complex-mediated reactions at any point before, during, or after antimicrobial treatment.