What is Leprosy?
Leprosy is an infectious disease caused by the bacteria Mycobacterium leprae. This bacteria infects the skin and peripheral nerves, initially leading to skin hypopigmentation, diminished sensation, and tender enlarged peripheral nerves. The face and hands are often involved. Individuals may eventually develop lumps and swelling of the face and other body regions, leading to disfigurement and disability if left untreated.
Leprosy most often occurs in countries such as India, Brazil, and Africa. Exposure in the United States is typically related to travel. Fortunately, the disease is not highly contagious and if diagnosed early, antimicrobial therapy is very effective.
What Causes Leprosy?
Leprosy is caused by the bacteria Mycobacterium leprae. The most likely mode of transmission is via the respiratory route. Most cases are spread by this mechanism in individuals exposed to known cases. The disease is not highly contagious and the majority of exposed individuals do not contract the disease. Once inhaled, the bacteria can disseminate throughout the body. The bacteria is occasionally be spread by entering breaks in the skin. There are also reports of transmission via contact with armadillos. Additional risk factors for leprosy include:
- Older age
- Genetic predisposition
Immunosuppression includes individuals with HIV/AIDS, those receiving chemotherapy, and individuals taking biologic agents for rheumatologic conditions.
How Common is Leprosy?
Most cases of leprosy are seen in countries such as India, Brazil, Indonesia, and Nigeria. In the United States, approximately 300 new cases occur annually – about 75% of these cases occur in immigrants.
Leprosy is more common in males compared to females. The condition typically requires referral to an infectious disease specialist.
Signs and Symptoms
Symptoms and signs of leprosy typically include:
- Hypopigmented skin patches
- Red skin patches
- Loss of sensation in involved areas
- Paresthesias – numbness/tingling sensation
- Painless wounds or burns
- Tender enlarged peripheral nerves
- Lump and swelling of the earlobes & face
Patients often have skin lesions that do not respond to treatment of common dermatologic ailments. A cardinal features is the presence of sensory loss within the lesions. Occasionally, individuals will report a painless cut or burn in the absence of an inciting injury. A history of travel or residence in a country where the condition is endemic is another clue.
Patients with leprosy frequent develop immunologic reactions characterized by a systemic inflammatory response. They may occur before, during, or after treatment – it affects 30%-50% of all patients with leprosy. Symptoms typically include:
- Constitutional symptoms - fatigue, malaise, & fever
- Nerve inflammation & pain (neuritis)
- Joint inflammation & pain (arthritis)
- Inflammation of the iris in the eye (iritis)
- Runny nose or nasal congestion (nasopharyngeal symptoms)
Severe cases may result in sepsis, paralysis, deformity. Patients must often be educated that these symptoms are not related to a drug-reaction and that therapy should be continued.
Early diagnosis and treatment of leprosy is critical in order to prevent long-term complications such as neuropathy, disfigurement, and disability. The diagnosis is suggested based on characteristic physical examination findings and confirmed with a full-thickness skin biopsy from the edge of the skin lesion. The biopsy specimen is subsequently analyzed for Mycobacterium leprae using polymerase chain reaction (PCR) testing and bacterial culture.
Your doctor may obtain basic laboratory studies such as a CMP (comprehensive metabolic panel) and CBC (complete blood cell count). Depending on your risk factors, they may also evaluate for HIV with antigen and antibody testing.
The treatment of leprosy typically consists of a multi-drug regimen. This typically consists of a 12-24 month combination of the following agents:
Nerve inflammation (neuritis) is normally treated with corticosteroids such as Deltasone (prednisone). Patients are generally evaluated with physical examination and basic laboratory studies every 3 months to asses for a clinical response as well as treatment complications. Patients with systemic immunologic reactions are normally continued on antimicrobial therapy, however, the rifampin dose may be reduced in these situations. Individuals in endemic areas are often vaccinated with Bacillus Calmette-Guérin, which can partially protect against the disease.
Relapses of Leprosy are rare, occurring approximately 5-10 years after treatment completion. Occasionally, relapse is difficult to distinguish from immunologic reaction. Treatment with corticosteroids usually leads to clinical improvement in individuals with immunologic reaction, but does not eradicate relapses.
- Global leprosy situation, 2010. Wkly Epidemiol Rec 2010; 85:337. - https://www.who.int/lep/resources/who_wer8535/en/
- Truman RW, Singh P, Sharma R, et al. Probable zoonotic leprosy in the southern United States. N Engl J Med 2011; 364:1626. - https://www.nejm.org/doi/full/10.1056/NEJMoa1010536
- Moschella SL. An update on the diagnosis and treatment of leprosy. J Am Acad Dermatol 2004; 51:417. - https://www.ncbi.nlm.nih.gov/pubmed/15337986
The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.