Leprosy or “Hansen’s disease” is a contagious disease caused by mycobacterium leprae complex. In 2000, leprosy was eliminated as a cause of public health concern. Yet, cases still occur, especially in resource-limited countries such as India, Nepal, and Bangladesh. The reservoirs of M.leprae are the armadillos and red squirrels. Moreover, the primary mode of transmission is thought to be respiratory droplets. Risk factors include contact with active cases, especially with the lepromatous type of leprosy, exposure to armadillos, immunosuppression, and age.

Leprosy can be classified into a mild tuberculoid form and a more severe lepromatous form, with intermediate stages in-between. Signs include red or hypopigmented skin patches and loss of sensation in the same skin patches. The lepromatous form presents with more generalized symptoms with erythematous skin nodules, thickening of earlobes, and loss of body hair. Complications include painful neuropathy, corneal ulceration, and abrasion. Late diagnosis and incomplete treatment of leprosy are associated with an increased burden of the disease, deformities, and stigma. The diagnosis is based on clinical presentation supported by the presence of acid-fast bacilli on full-thickness skin biopsy from the most active skin lesion. PCR for M. leprae DNA can also be used for diagnosis.

Leprosy is treated with multi-drug therapy (rifampicin, dapsone, and clofazimine). The duration ranges from 6 months for tuberculoid form and 12 months for lepromatous form. Drug resistance has been reported in some countries in which second-line drugs can be used, such as clarithromycin, minocycline, and fluoroquinolones.

Skin lesions usually start to resolve after few months to years if the patient is compliant with the drug regimen. Although rare, leprosy might relapse mostly 5 to 10 years after stopping the treatment. In areas with a high prevalence of leprosy, a single dose of BCG vaccine can give 50 percent protection. For contacts with active cases of leprosy, chemoprophylaxis with single-dose rifampicin can be given for adults and children more than two years.

Written by: Dr. Tammam Alanazi, Dermatology resident.

References:
1- WHO Guidelines for the Diagnosis, Treatment, and Prevention of Leprosy
2- UptoDate