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The lepromin skin test is used to determine what type of leprosy
Leprosy

Leprosy , or Hansen's disease , is a Chronic disease caused by the bacteria Mycobacterium leprae and Mycobacterium lepromatosis. Leprosy is primarily a granulomatous disease of the Peripheral nervous system and Mucous membrane of the upper respiratory tract; skin lesions are the primary external symptom....
 a person has. It involves the injection of a standardized extract of the inactivated "leprosy bacillus",(Mycobacterium leprae
Mycobacterium leprae

Mycobacterium leprae, also known as Hansen?s bacillus, mostly found in warm tropical countries, is the bacterium that causes leprosy ....
 or "Hansen's Bacillus") under the skin
Skin

The skin is the outer covering of the body, also known as the epidermis. It is the largest organ of the integumentary system made up of multiple layers of epithelial biological tissue, and guards the underlying muscles, bones, ligaments and organ s....
. It is not recommended as a primary mode of diagnosis
Diagnosis

Diagnosis is the identification of the nature of anything, either by process of elimination or other analytical methods. Diagnosis is used in many different disciplines, with slightly different implementations on the application of logic and experience to determine the cause and effect relationships....
.

xtract sample of inactivated Hansen's Bacillus is injected just under the skin, usually on the forearm, so that a small lump pushes the skin upward.






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The lepromin skin test is used to determine what type of leprosy
Leprosy

Leprosy , or Hansen's disease , is a Chronic disease caused by the bacteria Mycobacterium leprae and Mycobacterium lepromatosis. Leprosy is primarily a granulomatous disease of the Peripheral nervous system and Mucous membrane of the upper respiratory tract; skin lesions are the primary external symptom....
 a person has. It involves the injection of a standardized extract of the inactivated "leprosy bacillus",(Mycobacterium leprae
Mycobacterium leprae

Mycobacterium leprae, also known as Hansen?s bacillus, mostly found in warm tropical countries, is the bacterium that causes leprosy ....
 or "Hansen's Bacillus") under the skin
Skin

The skin is the outer covering of the body, also known as the epidermis. It is the largest organ of the integumentary system made up of multiple layers of epithelial biological tissue, and guards the underlying muscles, bones, ligaments and organ s....
. It is not recommended as a primary mode of diagnosis
Diagnosis

Diagnosis is the identification of the nature of anything, either by process of elimination or other analytical methods. Diagnosis is used in many different disciplines, with slightly different implementations on the application of logic and experience to determine the cause and effect relationships....
.

How the test is performed

An extract sample of inactivated Hansen's Bacillus is injected just under the skin, usually on the forearm, so that a small lump pushes the skin upward. The lump indicates that the antigen
Antigen

An antigen is a substance that prompts the generation of antibodies and can cause an immune response. The word originated from the notion that they can stimulate antibody generation....
 has been injected at the correct depth. The injection site is labeled and examined 3 days and 28 days later to see if there is a reaction.

People with dermatitis
Dermatitis

Dermatitis is a blanket term meaning any "inflammation of the skin" . There are several different types of dermatitis. The different kinds usually have in common an allergic reaction to specific allergens....
 or other skin irritations should have the test performed on an unaffected part of the body. If a child needs to have this test performed, it may be helpful to explain how the test will feel, and even practice or demonstrate on a doll
Doll

A doll is an object that represents a baby or other human being, but includes likenesses of animals and imaginary creatures. Dolls have been around since the dawn of human civilization, and have been fashioned from a vast array of materials, ranging from stone, clay, wood, bone, cloth and paper, to porcelain, china, rubber and plastic....
. The more familiar the child is with what will happen and why, the less anxiety
Anxiety

Anxiety is a psychological and physiological state characterized by cognitive, somatic, emotional, and behavioral components. These components combine to create an unpleasant feeling that is typically associated with uneasiness, fear, or worry....
 he or she will feel. When the antigen is injected, there may be a slight stinging or burning sensation. There may also be mild itching at the site of injection afterwards.

Normal values

People who don't have clinical leprosy (= Hansen's Disease, or HD) may have little or no skin reaction to the antigen, or may have a strong reaction to it. Patients with "lepromatous" (Virchowian) HD have no skin reaction to the antigen. This is because "lepromatous" patients' immune system specifically recognises, not the Hansen's bacillus, but instead the plasmid (or "transposon", or "ultravirus") that it carries attached to the inside of its cell wall. In other words, this group of the population has a specific anergy to Hansen's bacillus itself, the "price" for recognition of the associated neuron invasion threat that the bacillus carries. The plasmid harboured by Hansen's bacillus contains a replicator gene which it must share with its procaryote host, and a neuron invasion gene. Virchowian ("lepromatous") patients' macrophages (Virchow cells) stop the plasmid escaping from the bacillus into their peripheral nerves which would result in nerve damage. How does this immune defense system work? Once the Hansen's bacilli are engulfed by Virchow cells, the Virchow cell effects detachment of the plasmid from the bacterial cell wall, so that the threat of nerve invasion is averted. The detached plasmid re-integrates into the Hansen's Bacillus chromosome, allowing the bacillus to divide unchecked (resulting in "lepromatous" = Virchowian - skin nodules).

By contrast, a positive Fernandez reaction
Fernandez reaction

The Fernandez reaction is reaction that occurs to signal a positive result in the lepromin skin test for leprosy. The reaction occurs in the skin at the site of injection if the body possesses antibody to the Dharmendra antigen, one of the antigens found in Mycobacterium leprae, the bacteria that causes leprosy....
 is seen in the skin of patients with tuberculoid and borderline tuberculoid Hansen's Disease. Patient's with this form of HD have an immune system that does not recognise the molecular parasite (plasmid) carried at the surface of the Hansen's bacillus lodged in their skin, but, instead, recognises the bacillus itself as foreign. Thus, the plasmid, with its replicator gene, is not prevented from moving out of the bacillus into neighboring human nerves where it replicates, damaging those nerves and causing the tuberculoid HD clinical picture. The bacillus, meanwhile, is rendered unable to divide (having lost its replicator gene) and is destroyed by the immune system in the normal way.

Risks

There is an extremely small risk of an allergic reaction
Allergy

Allergy is a Disorder of the immune system often also referred to as atopy. Allergic reactions occur to Natural environmental substances known as allergens; these reactions are Acquired disorder, predictable and rapid....
 which may include itching and rarely hives.

Source

. Medline Plus Medical Encyclopedia. Update Date: 8/15/2003. By Daniel Levy, M.D., Ph.D., Infectious Diseases, Greater Baltimore Medical Center
Greater Baltimore Medical Center

Greater Baltimore Medical Center, known to many simply as GBMC, is a hospital located in the Baltimore suburb of Towson, Maryland. GBMC serves more than 26,700 inpatient cases and approximately 60,000 emergency room visits annually....
, Baltimore, Maryland
Maryland

Maryland is a U.S. state located in the Mid Atlantic States of the United States, bordering Virginia, West Virginia and the Washington, D.C. to the south and west, Pennsylvania to the north, and Delaware to the east....
, USA. Review provided by VeriMed Healthcare Network. Text in the US Federal Government public domain.

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