Leprosy (Hansen's Disease)
Primary Distribution: Tropical and sub-tropical Africa, Asia, Pacific Islands, South America, Central America, and Mexico. Countries reporting the most cases in 1997 were Bangladesh, Brazil, India, Indonesia, Myanmar, and Nigeria (CDC, 1998).
Agent and Vector: The acid-fast rod Mycobacterium leprae is transmitted probably via the respiratory route through prolonged exposure in childhood. Incubation: Usually 2-5 years; and up to 20 years.
Clinical Findings and Treatment
Signs and Symptoms: There are two basic types of leprosy: lepromatous leprosy (LL) and tuberculoid leprosy (TL). Either of these may be classified as borderline (borderline lepromatous or BL and borderline tuberculoid or BT). Patients who fall between the two basic types may be classified as borderline borderline (BB); and patients with vaguely defined (often early) lesions may be classified as indeterminate (I). Most initial infections involve few symptoms and spontaneous recovery is common, with a minority of patients developing clinical disease. Initial lesions tend to be vaguely defined hypopigmented or erythematous macules, i.e., indeterminate.
Complications: Erythema nodosum leprosum (ENL) is an antigen-antibody complex reaction (to therapy) occurring in many patients with LL and BL. Symptoms may occur before or during treatment and include acute onset of tender erythematous nodules, arthritis, iritis, and neuritis. Glomerulonephritis and/or amyloidosis may also occur as part of ENL. Persons at greatest risk for ENL include those with LL, skin infiltration or bacterial index > 4+, age younger than 40 years, and a previous episode of ENL. Reversal reaction is also a consequence of therapy and is similar to ENL, except that systemic symptoms are not present. Reversal reactions can cause rapid irreversible nerve damage, hence must be quickly managed as discussed below. Persons with the Lucio form of LL are prone to developing septicemia leading to death. Renal failure and hepatomegaly may result from secondary amyloidosis in long-standing disease. Advanced leprosy with disability and disfigurement is less common world-wide than in previous times and is essentially non-existent in the Western world.
Diagnosis: Advanced lesions may be accurately diagnosed on physical findings. Pathologists familiar with the histopathology of leprosy are able to provide diagnosis based on skin or involved nerve biopsy. Early lesions and other symptoms require laboratory testing, which may include demonstration of acid-fast bacilli in a skin biopsy or detection of antibodies to the Mycobacterium leprae. Slit skin smear examination of lesions yields various levels of accuracy in diagnosis, with significant numbers of false negatives.
Differential Diagnosis: Among the differential diagnoses for leprosy are (for skin lesions) leishmaniasis, granuloma annulare, granuloma multiforme, lupus erythematosus, lupus vulgaris, psoriasis, pityriasis rosea, yaws, sarcoidosis; and (for peripheral neuropathies) carpal tunnel syndrome, diabetic neuropathy, primary amyloidosis of nerves, and familial hypertrophic neuropathy. Chronic skin disease + peripheral neuropathy are suspicious of leprosy.
Treatment: Because of the development of dapsone-resistance, combination therapy is the current accepted standard for all types of leprosy. Patients with borderline or lepromatous leprosy should be treated with a multi-drug regimen such as dapsone 50-100 mg po daily, clofazamine 50 - 200 mg po daily, and rifampin 600 mg/day or 10 mg/kg daily for at least 2-3 years until all biopsies are negative for acid-fast bacilli. Clofazamine is not safe in pregnancy. Patients with indeterminate or tuberculoid leprosy may be treated with dapsone and rifampin as above for 6-12 months, followed by dapsone alone for a total of at least two years of therapy. Monocycline, ofloxacin, and clarithromycin show promise in the treatment of rifampin-resistant leprosy. ENL and reversal reactions are treated with prednisone 60 mg/day for several days until improvement is seen; then tapered over several weeks. ENL may be treated with thalidomide 150-200 mg bid for several days and then tapered over several weeks. Chronic ENL can be treated with thalidomide as above, tapered to a maintenance dose of 50-100 mg/hs. Thalidomide is absolutely contraindicated in pregnancy.
Centers for Disease Control and Prevention (1998). Hansen's Disease (Leprosy). Available online: http://www.cdc.gov/ncidod/dbmd/diseaseinfo/hansens_t.htm
Gelber, R.H. (1997). Regimens to treat lepromatous leprosy. Antimicrobial Agents and Chemotherapy. 41(7), 1618-1619.
Goldsmith, R.S. (1999). Infectious diseases: Protozoal and helminthic. In L.M. Tierney, S.J. McPhee, & M.A. Papadakis (Eds.), Current Medical Diagnosis & Treatment (14th ed.) (pp.1353-1417). Stamford Connecticut: Appleton & Lange.
Manandhar, R., LeMaster, J.W., & Roche, P.W. (1999). Risk factors for erythema nodosum leprosum. International Journal of Leprosy and Other Mycobacterial Diseases. 67(3), 270-278.
Miller, R.A. (1998). Leprosy (Hansen's disease). In A.S. Fauci, E. Braunwald, K.J. Isselbacher, J.D. Wilson, J.B. Martin, D.L. Kasper, S.L. Hauser, & D.L. Longo (Eds.), Harrison's Principles of Internal Medicine (14th ed.) (pp. 1014-1019). New York: McGraw-Hill.
Myers, W.A. (1991). Leprosy. In G.T. Strickland (Ed.), Hunter's Tropical Medicine (7th ed.) (pp. 483- 494). Philadelphia: W.B. Saunders Company.
Rosenblatt, J.E. (1999). Antiparasitic agents. Mayo Clinic Proceedings. 74(11), 1161-1175.
Sarkar, R., Kaur, I., Das, A., & Sharma, V.K. (1999). Macular lesions in leprosy: A clinical, bacteriological, and histopathological study. Journal of Dermatology. 26(9), 569-576.