A man with nodular leprosy on his face
Leprosy (Normal quality)
Leprosy is a mycobacterial infection caused by mycobacterium leprae (M. leprae) that primarily affects the peripheral nerves and skin, especially in the cooler parts of the body due to the bacteria growing better at 27-34°C. Overall leprosy comes in two major varieties: the less severe tuberculoid and the more severe lepromatous leprosy. Both subtypes show different immunologic response profiles at sites of disease: tuberculoid leprosy (TL) is characterized by a more powerful TH1 immune response (characterized by high mRNA expression of IL-2, IL-12 and IFN-γ) whereas lepromatous leprosy (LL) is characterized by a greater TH2 cell-mediated response (with a high level of IL-4, IL-5 and IL-10 mRNA expression) and humoral response. It is worth noting that leprosy is generally described as a continuous spectrum between lepromatous and tuberculoid variants, with most patients having evidence of both TH1 and 2 responses in their lesions, with one usually dominating to some extent.
Erythema nodosum leprosum, (ENL) a rare inflammatory skin reaction caused by the body's immune response against the microbe and is seen in lepromatous forms of leprosy. ENL was the first disease that thalidomide was approved to treat in the U.S., in 1998, as it was discovered that in ENL thalidomide produces rapid and robust[note 1] improvements in moderate-severe ENL. In ENL it seems like thalidomide works by inhibiting the secretion of tumour necrosis factor alpha (TNF-α) a pro-inflammatory protein secreted by the immune system. Despite its clinical effectiveness, because of its risk of causing birth defects (including a 40% mortality rate in infants born to mothers who took the drug whilst pregnant) the World Health Organization (WHO) has consistently recommended against its use in ENL.
Interestingly most people are naturally immune to leprosy nowadays, which is likely testament to how long our species has battled against the microbe in the past as this battle could leave marks in the form of favouring genes that convey immunity to the microbe. There exists a vaccine that provides some protection from tuberculosis and leprosy (the BCG vaccine) but the protection from it is limited and even after the vaccine some people still get these diseases after exposure, despite a healthy immune system. The BCG vaccine, btw, is also administered into the bladder of patients with bladder cancer where it is in fact a very effective treatment against the cancer. This likely reflects how immunogenic (i.e., how efficiently mycobacterial organisms elicit an immune response) these organisms are as a consequence of BCG vaccination in bladder cancer is the cancer cells get caught in the immune system's cross-fire.
- NCBI Bookshelf provides free book resources on this topic.
- PubMed provides review articles from the past five years (limit to free review articles or to systematic reviews)
- The TRIP database provides clinical publications about evidence-based medicine.
- ↑ And is superior to all other known treatments.
- ↑ 1.0 1.1 Smith, DS; Katta, SR (22 July 2014). Lopez, FA; Talavera, F; Sanders, CV; Bronze, MS; Ramachandra, T, ed. "Leprosy". Medscape Reference. New York, USA: WebMD. Retrieved 16 January 2015.
- ↑ 2.0 2.1 2.2 Kumar, V; Abbas, AK; Aster, AC (July 2014). "Chapter 8. Infectious Diseases". Robbins & Cotran Pathologic Basis of Disease 9e. Philadelphia, USA: Saunders. pp. 377–378. ISBN 978-0-8089-2450-0.
- ↑ Lewis, FS; Conologue, TD; Harrop, E (9 April 2014). Barrett, TL; Wells, MJ; Libow, LF; Quirk, CM; Elston, DM, ed. "Dermatologic Manifestations of Leprosy". Medscape Reference. New York, USA: WebMD. Retrieved 16 January 2015.
- ↑ Kahawita, IP; Walker, SL; Lockwood, DNJ (February 2008). "Leprosy type 1 reactions and erythema nodosum leprosum". Anais Brasileiros de Dermatologia 83 (1): 75–82. doi:10.1590/S0365-05962008000100010.
- ↑ World Health Organization. "WHO Guidelines for the management of severe erythema nodosum leprosum (ENL) reactions" (PDF). Geneva, Switzerland: World Health Organization. Retrieved 16 January 2015.