A lepromin skin test is used to determine the type of leprosy a person has contracted. The lepromin skin test is also called the leprosy skin test.

Leprosy is a long-term (chronic) condition caused by the bacteria Mycobacterium leprae. The disease is commonly found in Asia and Africa and is transmitted through mucus or secretions from the nose, eyes, and mouth of an infected person. The disease has a long incubation time. The symptoms usually don’t begin for more than a year and progress slowly.

Leprosy affects the following parts of the body:

  • skin
  • nerves
  • eyes
  • upper respiratory tract

In men, the disease can affect the testes.

Leprosy used to be a significant public health concern worldwide. However, the World Health Organization reports that the prevalence of the disease has been reduced to less than 1 per 10,000 people as of 2000, due to the use of multidrug therapy.

The disease can be effectively treated and even cured if it’s caught in the early stages. Once leprosy has been diagnosed, your doctor must determine which type of leprosy you have to develop a treatment plan.

The symptoms of leprosy include:

  • skin lesions that don’t heal for several weeks or months
  • skin lesions that are lighter in color or are less sensitive to heat, pain, or touch than unaffected skin
  • skin thickening or scarring
  • nerve damage leading to numbness or lack of sensation in the extremities
  • a weakening of the muscles that gets worse over time

A skin biopsy is commonly used to diagnose leprosy. A skin biopsy involves removing a small section of skin for laboratory testing. If you have the symptoms of leprosy, a lepromin skin test may be ordered along with a biopsy to confirm both the presence and type of leprosy.

There are several types of leprosy, ranging from mild (indeterminate) to severe (lepromatous). Depending on the clinical features of the disease, leprosy may be classified as:

  • indeterminate leprosy
  • tuberculoid leprosy
  • borderline tuberculoid leprosy
  • borderline leprosy
  • borderline lepromatous leprosy
  • lepromatous leprosy

Your doctor must determine which type of leprosy you have to provide the correct treatment.

A lepromin skin test is performed by injecting a small sample of inactivated M. leprae under your skin. The term “inactivated” means that the bacterium isn’t able to cause infection. The bacterium is usually injected into the forearm. A small lump will form at the injection site, indicating that the correct amount of bacterium has been injected at the correct depth in the skin for the test to be effective.

You’ll need to be examined three days after the injection to see if you’ve had a reaction to the bacterium. If no reaction occurs, you’ll need to be examined again in 28 days. Specific reactions at the injection site indicate certain types of leprosy.

No preparation is necessary for this test. If you have skin irritation or a skin disorder such as dermatitis, the injection should be made on a part of your skin that isn’t affected. Skin redness or irritation due to an unrelated skin disorder may produce a false-positive result on the lepromin skin test. Performing the test on an unaffected area will help to ensure that the test is accurate.

The risks associated with a lepromin skin test are minor. The injection may cause a slight burning or stinging sensation. The injection site may also be itchy after the injection.

In very rare cases, an allergic reaction may occur following the injection. An allergic reaction may result in shortness of breath and itching. Hives can also occur, but this is rare.

If these symptoms occur, get help from your doctor to ensure that the reaction isn’t serious.

The results of the lepromin skin test are based on changes in the skin that occur at the injection site. Redness, swelling, or other skin changes indicate the presence of tuberculoid and borderline tuberculoid leprosy. If you’ve tested positive for leprosy during a biopsy but don’t have a skin reaction, you may have lepromatous leprosy.

If your biopsy and skin test indicate that you have any form of leprosy, your doctor will most likely prescribe the antibiotics dapsone, rifampin (Rifadin), and clofazimine (Lamprene), which you may have to take for months or even years to treat the disease.