Hesperian Health Guides
Diagnosing Leprosy
Although skin patches are often the first sign of leprosy, many other diseases can cause similar patches. Only when there is a loss of feeling inside the skin patch, as compared with the skin outside the patch, can we be almost sure the person has leprosy. However, in some forms of leprosy, loss of feeling in skin patches may develop only years later, or not at all. Therefore, other evidence of leprosy must be looked for.
Another sign of leprosy—tingling, numbness, or loss of feeling in hands and feet— may also have other causes.
To make a fairly certain diagnosis of leprosy, the person should have at least 1 of these 3 major signs:
| 1. definite loss or change of feeling in skin patches Note: Leprosy patches on face often do not lose feeling as much as on other parts of the body. |
 Do you feel this?
Yes - but not the same as when you touched me in other places. |
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2. definite enlargement of nerves (See nerves to check) |
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| 3. presence of leprosy bacilli in a skin smear A split skin smear is prepared by cutting a thin layer of skin from a skin patch. Less commonly it is taken from the moist skin deep inside the nose—an area that is often heavily infected. The skin sample is placed on a glass slide, colored with special stains, and examined with a microscope. |
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leprosy bacilli as seen in the microscope. |
| taking a “split skin smear” from a skin patch | |||
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The bacteria (bacilli) of leprosy, if present, can be seen under the microscope.
Whenever you suspect leprosy but the diagnosis is uncertain, a skin smear should be taken (by a trained worker).
Note: Not many persons with leprosy show all 3 of these signs. Persons with loss of feeling in skin patches usually have no bacilli in their skin smears.
This page was updated:25 Nov 2024