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Hanseniasis, Leprosy

What is it?

Hanseniasis is an infectious disease, with chronic course (long duration) caused by Mycobacterium leprae, microorganism which affects primarily skin and nerves of the extremities of the body. The disease has a history of prejudice that does not make sense any more, as it can be treated and healed.

Transmission is from person to person by droplets germs eliminated by the speech and are inhaled by other people entering the body by the the nose mucosa. Another possibility is the direct contact with the skin through the wounds of patients.

However, it requires a prolonged and intimate contact for contamination, such as family members living in the same residence. Hence the importance of screening family members of the leprosy patient.

Most of the adult population is resistant to leprosy, but children are more susceptible, usually getting the disease from a infected person in the family. The incubation period ranges from 2 to 7 years and among the predisposing factors are low socioeconomic status, malnutrition and overcrowded homes. Because of this, the disease still has a major impact in developing countries.

Characteristics and symptoms

The manifestations of leprosy depend on the host immune response to the bacillus that causes the disease. This response can be checked by the Mitsuda test, which does not diagnose the disease, only evaluates an individual's resistance to the bacillus. A positive result means good defense, a negative result, no defense and an uncertain result, intermediate defense. According to that, we have the following forms of the disease:

  • Indeterminate hanseniasis: initial form, it evolves spontaneously to cure in most cases and to other forms of the disease in about 25% of cases. Generally, there is only one lesion, lighter in color than normal skin, with decreased sensitivity. More common in children.
  • Tuberculoid hanseniasis: more benign and localized form, occurs in people with high resistance to the bacillus. The lesions are few (or single), well-defined and slightly elevated and with no sensitivity (numbness). There are changes in the nerves near the lesion that may cause pain, weakness and muscle atrophy.
  • Borderline hanseniasis: intermediate form that is a result of intermediate immunity. The number of lesions is higher and can affect large areas of skin, mixed with areas of healthy skin. Involvement of the nerves is more extensive.
  • Lepromatous hanseniasis: in these cases, immunity is null and bacillus undergo intense multiplication, leading to a more severe, with anesthesia of the feet and hands that favor injuries and wounds that lead to deformities, muscle atrophy, swelling of legs and emergence of elevated lesions in the skin (nodules). Internal organs are also affected by the disease.

Borderline hanseniasis

Leprosy can experience periods of immune alterations, known as reactive states. In borderline leprosy, the lesions become red and the nerves inflamed and sore. In the lepromatous type, appears as erythema nodosum: nodular, indurated and painful lesions on the legs, arms and face, which are accompanied by fever, malaise and inflammation of internal organs. These reactions may occur even in patients who have finished treatment, which does not mean that the disease was not cured.


Leprosy is treatable and curable with specific drugs against the bacillus. The duration of treatment varies with the form of the disease: 6 months for the milder and 12 months for the more severe forms.

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