Leprosy: Causes, Risk Factors, Types, Symptoms, Diagnosis, Treatment, Complications and Prevention

It is an infectious disease that causes severe and disfiguring skin ulcers and damage to the nerves, arms, legs, and areas of skin around the body.

Since antiquity, the disease has existed, often surrounded by negative stigmas and terrifying stories of patients infected with leprosy who are rejected as outcasts.

The outbreaks of leprosy have affected and have caused people to panic on all continents.

The oldest civilizations in China, Egypt, and India feared that leprosy was an incurable, mutilating, and contagious disease.

However, leprosy is not that contagious. You can infect it only if you come in close and repeated contact with the nose and mouth drops of someone with untreated leprosy.

Children are more likely to get leprosy than adults.

According to the World Health Organization, around 180,000 people worldwide are infected with leprosy, and most of them are found in Africa and Asia.


About 100 people are diagnosed with leprosy in the United States each year, mainly in the southern states such as California and Hawaii.


Leprosy is caused mainly by Mycobacterium leprae, a rod-shaped bacillus that is an obligate intracellular bacterium (it only grows inside specific human and animal cells).

M. leprae is genetically related to M. tuberculosis (the type of bacteria that causes tuberculosis ) and other mycobacteria that infect humans.

As with malaria, patients with leprosy produce anti-endothelial antibodies (antibodies against the tissues of blood vessels), but the role of these antibodies in these diseases is still under investigation.

In 2009, researchers discovered a new Mycobacterium species, M. lepromatosis, that causes diffuse disease (lepromatous leprosy).

This new species (determined by genetic analysis) was found in patients located in Mexico and the Caribbean islands.

How is leprosy transmitted?

The researchers suggest that M. leprae is transmitted from person to person by nasal secretions.

However, the disease is not as contagious as the flu. They speculate that the infected droplets reach the nostrils of other people, and the infection begins there.

Some researchers suggest that infected droplets can infect others by breaking the skin. M. leprae apparently can not infect intact skin.

Rarely do humans contract leprosy from the few animal species mentioned above.

The presence of animals makes it difficult to eradicate leprosy from endemic sources.

Recent genetic studies have shown that several genes (around seven) are associated with increased susceptibility to leprosy.

Some researchers currently conclude that susceptibility to leprosy may be partially heritable.

Risk factor’s

The people most at risk live in areas where leprosy is endemic (parts of India, China, Japan, Nepal, Egypt, and the other regions) and especially those in constant physical contact with infected people.

In addition, there is some evidence that genetic defects in the immune system may cause certain people to be more likely to become infected (region q25 on chromosome 6).

People who handle certain animals that carry the bacteria (for example, armadillos, African chimpanzees, mangabey soot, and cynomolgus macaque) risk getting the bacteria from the animals, especially if they do not wear gloves during contact.


Unfortunately, leprosy’s first signs and symptoms are very subtle and occur slowly (usually over the years).

The symptoms are similar to those of syphilis, tetanus, and leptospirosis. The following are the main signs and symptoms of leprosy:

  • Numbness (between the first symptoms).
  • Loss of temperature sensation (between the first symptoms).
  • Reduced tactile feel (between the first symptoms).
  • Feelings of pins and needles (between the first symptoms).
  • Pain in the joints.
  • The feelings of deep pressure diminish or are lost.
  • Nervous injury
  • Weightloss.
  • Blisters and rashes.
  • Ulcers are relatively painless.
  • Cutaneous lesions of hypopigmented macules (flat and pale areas of the skin that lost color).
  • Damage to the eyes (dryness, reduced blinking).
  • Extensive ulcerations (symptoms and following signs).
  • Hair loss (for example, loss of eyebrows).
  • Facial disfigurement (for example, nose loss) (symptoms and later signs).

This sequence of long-term development events begins and continues in the colder areas of the body (for example, hands, feet, face, and knees).


The diagnosis of leprosy is most commonly based on clinical signs and symptoms.

These are easy to observe and obtain by any health worker after a short training period.

In practice, most people with such complaints report themselves to the health center.

Only in rare cases is there a need to use the laboratory and other research to confirm a diagnosis of leprosy.

In a country or endemic area, it must be considered that a person has leprosy if it shows one of the following cardinal signs:

  • Skin lesion compatible with leprosy and with definite sensory loss, with or without thickened nerves.
  • Positive smears of the skin.

The skin lesion may be single or multiple, usually less pigmented than the surrounding normal skin.

Sometimes the lesion is reddish or copper-colored. A variety of skin lesions can be seen, but macules (flat), papules (raised), or nodules are common.

Sensory loss is a typical characteristic of leprosy. The skin lesion may show a loss of sensitivity to puncture and light touch.

Thickened nerves, mainly peripheral nerve trunks, are another feature of leprosy.

A thickened nerve is often accompanied by other signs resulting from nerve damage.

These can be a loss of sensitivity in the skin and weakness of the muscles supplied by the affected nerve.

In the absence of these signs, nerve thickening by itself, without sensory loss and muscle weakness, is often not a reliable sign of leprosy.

Smear-positive skin In a small proportion of cases, leprosy rod-shaped and red bacilli, which are diagnostic of the disease, can be seen in the smears taken from the affected skin when examined under a microscope after a stain appropriate.

A person presenting with skin lesions or symptoms suggestive of nerve damage, in whom the cardinal signs are absent or doubtful, should be called a “suspicious case” without an immediately apparent alternative diagnosis.

These people should be informed of the basic facts of leprosy and are recommended to return to the center if the signs persist for more than six months or if worsening is noticed.

Suspicious cases can also be sent to referral clinics with more facilities for diagnosis.


There are three systems for classifying leprosy. The first system recognizes two types of leprosy: tuberculoid and lepromatous.

A person’s immune response to the disease determines their type of leprosy.

The immune response is good, and the disease only has some lesions (skin sores) in tuberculoid leprosy. The condition is mild and only mildly contagious.

The immune response is poor in lepromatous leprosy and affects the skin, nerves, and other organs. There are lesions and disseminated nodules (large lumps and bumps). This disease is slightly more contagious.

The WHO categorizes the disease according to the type and number of affected areas of the skin.

The first category is paucibacillary, in which five or fewer lesions without bacteria are detected in the skin sample.

The second category is multibacillary, in which there are more than five injuries; bacteria are detected in the cutaneous smear or both.

Finally, clinical studies use the Ridley-Jopling system.

It has six classifications based on the severity of the symptoms. These are:

  • Leprosy intermediate: some flat lesions that sometimes heal by themselves and can progress to a more severe type.
  • Tuberculoid leprosy: some flat lesions, some large and numb, some nervous involvement, may heal on its own, persist, or progress to a more severe form.
  • Borderline tuberculoid leprosy: lesions similar to tuberculoid but smaller and more numerous, more minor nerve augmentation; it can persist, return to tuberculoid, or advance to another form.
  • Leprosy at the edge of the line: reddish plaques, moderate numbness, swollen lymph nodes; can retreat, persist or progress to other forms.
  • Lepromatous leprosy bordering: many injuries that include flat lesions, elevated lumps, plaques, and nodules, sometimes numb; it can persist, regress or progress.
  • Lepromatous leprosy: many lesions with bacteria; hair loss, nervous involvement, weakness of the extremities, disfigurement; it does not recede.


Most cases (mainly clinically diagnosed) are treated with antibiotics.

The recommended antibiotics, their doses, and the time of administration are based on the form or classification of the disease and whether the patient is supervised or not by a medical professional.

In general, paucibacillary leprosy is treated with two antibiotics, dapsone, and rifampicin, while multibacillary leprosy is treated with two plus a third antibiotic clofazimine.

Usually, antibiotics are given at least six to 12 months or longer to cure the disease.

Antibiotics can treat paucibacillary leprosy, leaving little or no residual effect on the patient.

It is possible to avoid that the multibacillary leprosy advances and that the M. leprae live; this can be eliminated essentially from the person with antibiotics, but the damage that occurs before they are administered is generally not reversible.

Recently, the WHO suggested that single-dose treatment of patients with a single skin lesion with rifampin, minocycline (Minocin), or ofloxacin (Floxin) is effective.

Studies of other antibiotics are ongoing.

Depending on the above criteria, each patient has a schedule for their treatment, so the treatment schedules must be planned by a clinician familiar with the initial diagnostic classification of that patient.

Steroid medications have been used to minimize the pain and acute inflammation caused by leprosy; however, the controlled trials showed no significant long-term effects on nerve damage.

The role of surgery in the treatment of leprosy occurs after medical therapy (antibiotics) has been eliminated or acid-fast bacilli are not detected. They are often only needed in advanced cases.

The surgery is individualized for each patient to try cosmetic improvements and, if possible, restore the function of the extremities and some neuronal tasks that were lost with the disease.

As in the case of many diseases, home remedies are highly sought after.

For example, a paste made from the Hydrocotyle plant, also known as Cantella Asiatica, and even aromatherapy with incense has been suggested.

Patients are advised to discuss any home remedy with their doctor before using such methods; There is often little or no scientific information to keep these healing claims.


Without treatment, leprosy can permanently damage the skin, nerves, arms, legs, feet, and eyes. Complications of leprosy may include:

  • Blindness or glaucoma.
  • Disfigurement of the face:  including permanent swelling, bumps, and lumps.
  • Erectile dysfunction and infertility in men.
  • Renal insufficiency.
  • Muscle weakness: leading to claw-like hands or inability to flex the feet.
  • Permanent damage to the inside of the nose:  it can cause nosebleeds and a chronic congested nose.
  • Permanent damage to the nerves outside the brain and spinal cord: including those in the arms, legs, and feet.

Damage to the nerves can cause a dangerous loss of sensitivity.

A person with nerve damage related to leprosy may not feel pain when the hands, legs, or feet are cut, burned, or injured.


Exclude people with leprosy from child care, preschool, school, and work until an infectious disease doctor, a dermatologist, or a doctor in the Communicable Disease Control Division has approved their return.

Control is best achieved by rapidly eliminating infectivity in people with leprosy who use multidrug therapy.

Because close and prolonged contact is required for transmission, travelers to areas where leprosy is present have a shallow risk of contracting the disease.