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Medical Author:

Charles Patrick Davis, MD, PhD

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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Medical Editor:

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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In this Article

• Leprosy (Hansen's disease) facts
• What is leprosy?
• What is the history of leprosy (Hansen's disease)?
• What causes leprosy?
• What are the risk factors for leprosy?
• What are leprosy symptoms and signs?
• Are there different forms (classifications) of leprosy?
• How is leprosy transmitted?
• How is leprosy diagnosed?
• What is the treatment for leprosy?
• What are the complications of leprosy?
• How is leprosy prevented?
• What is the prognosis (outcomes) of leprosy?
• Where can I find more information on leprosy?
• Leprosy Index

Researchers suggest that M. leprae are spread person to person by nasal secretions or droplets. However, the disease is not highly contagious like the flu. They speculate that infected droplets reach other peoples' nasal passages and begin the infection there. Some investigators suggest the infected droplets can infect others by entering breaks in the skin. M. leprae apparently cannot infect intact skin. Rarely, humans get leprosy from the few animal species mentioned above. Occurrence in animals makes it difficult to eradicate leprosy from endemic sources. Routes of transmission are still being researched for leprosy. Recent genetic studies have demonstrated that several genes (about seven) are associated with an increased susceptibility to leprosy; some researchers now conclude that susceptibility to leprosy may be partially inheritable.

The majority of cases of leprosy are diagnosed by clinical findings, especially since most current cases are diagnosed in areas that have limited or no laboratory equipment available. Hypopigmented patches of skin or reddish skin patches with loss of sensation, thickened peripheral nerves, or both clinical findings together often comprise the clinical diagnosis. Skin smears or biopsy material that show acid-fast bacilli with the Ziehl-Neelsen stain or the Fite stain (biopsy) can diagnose multibacillary leprosy, or if bacteria are absent, diagnose paucibacillary leprosy. Other tests can be done, but most of these are done by specialized labs and may help a clinician to place the patient in the more detailed Ridley-Jopling classification and are not routinely done (lepromin test, phenolic glycolipid-1 test, PCR, lymphocyte migration inhibition test or LMIT). Other tests such as CBC test, liver function tests, creatinine test, or a nerve biopsy may be done to help determine if other organ systems have been affected.