What Is the Lepromin Skin Test?
A lepromin skin test is
used to determine the type of leprosy a patient has contracted. The lepromin
skin test is also called the leprosy skin test.
Leprosy is a
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:
- 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 by 90 percent with the use of multidrug therapy. It fell from 21.1 per
10,000 people in 1991 to less than one per 10,000 people in 2000.
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.
Symptoms of Leprosy
The symptoms of leprosy include:
- skin lesions that don’t heal for several weeks
- 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 which gets worse over
Why Is the Test Ordered?
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.
Types of Leprosy
There are several types of leprosy, ranging from
mild, or indeterminate, to severe, or lepromatous. Depending on the clinical
features of the disease, leprosy may be classified as:
- indeterminate leprosy
- tuberculoid leprosy
- borderline tuberculoid leprosy
- borderline borderline leprosy
- borderline lepromatous leprosy
- lepromatous leprosy
Your doctor must determine which type of leprosy you have to
provide the correct treatment.
How Is the Test Performed?
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.
Preparing for the Test
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.
What Are the Risks of the Test?
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.
Understanding the Test Results
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,
which you may have to take for months or even years to treat the disease.