What is Leprosy (Hansen Disease)?
Leprosy, also known as Hansen disease, is a long-term infection usually caused by two types of bacteria: Mycobacterium leprae and Mycobacterium lepromatosis. These bacteria mainly affect the skin and the nerves on the outside parts of the body.
These two bacteria are part of the same group known as the “Mycobacterium leprae complex”. While their DNA sequences are different enough that they are classified as separate species, they live only inside host cells, share many similar characteristics, and cause the same kind of disease.
Leprosy is an important topic in the healthcare world. Despite common myths, leprosy isn’t highly contagious, and effective treatments are available. Through increased public awareness and early treatment, we can greatly reduce the disabilities it causes to the eyes, hands, and feet. While it’s rare for leprosy to return after treatment, any nerve damage it has caused is permanent and might need lifelong care.
What Causes Leprosy (Hansen Disease)?
M. leprae is a type of bacteria that is part of the Mycobacterium leprae complex, along with M. lepromatosis. These bacteria are extremely slow-growing, with one generation taking 12 to 13 days to develop. They only live inside the cells of other organisms and can’t be grown in a lab. They have fewer functioning genes than the tuberculosis bacteria.
Tests have found that M. leprae grows best at temperatures between 27 to 33 degrees Celsius (80.6 to 91.4 degrees Fahrenheit), which is cooler than normal body temperature. This means they’re more likely to spread in the cooler areas of the body like the skin, nerves close to the skin, or the upper respiratory tract.
This bacteria also thrives in the nine-banded armadillo, which is common in the south-central United States and has a body temperature of 34 degrees Celsius (93.2 degrees Fahrenheit). It’s also been found in certain monkeys and chimpanzees.
Scientists have studied the genomes (the complete set of genes or genetic material in a cell or organism) of M. leprae and M. lepromatosis and found a lot of pseudogenes, which are like normal genes but don’t function properly. They’ve also found that some key genes needed for metabolism are missing. Because of these pseudogenes, the bacteria are able to thrive inside the cells of other organisms.
Recent studies have shown variations in the genetic sequences of M. lepromatosis. This led scientists to suggest that M. leprae and M. lepromatosis could have split from a common ancestor over 13 million years ago.
Risk Factors and Frequency for Leprosy (Hansen Disease)
The World Health Organization (WHO) declared leprosy as completely eradicated in 2000. This meant the disease’s prevalence had fallen to under 1 case per 10,000 people. Between 1985 and 2011, reported cases decreased massively from 5.4 million to around 219,000. By 2011, the number of cases per 10,000 people had dropped from roughly 21.1 to 0.37, with Europe excluded from these figures.
Leprosy is chiefly found in developing countries, with varying levels of prevalence. About 16 countries reported approximately 1000 new cases in 2009, with the majority in India, Indonesia, Brazil, Nigeria, and Bangladesh. However, it’s important to note that not all cases are reported. In Bangladesh, researchers went house-to-house and found almost five times more cases than were self-reported.
In the United States, 75 percent of leprosy cases were among immigrants. In cases involving US-born citizens, international exposure was typically the contributing factor. Some also contracted the disease from infected armadillos. The disease is generally seen more in males, with a ratio of roughly 3 to 2. In 2009, 61 percent of new patients had multibacillary cases, a type of leprosy, though this statistic varied from 33 to 94 percent across the globe.
Signs and Symptoms of Leprosy (Hansen Disease)
Leprosy is a complicated disease that can present in many different forms due to the varied immune responses it triggers. The Ridley-Jopling classification system provides a comprehensive breakdown of the various forms of leprosy, from the intense immune response associated with tuberculoid leprosy to the less intense response associated with multibacillary forms of the disease.
This classification system includes:
- Tuberculoid leprosy (TT)
- Borderline tuberculoid (BT)
- Mid-borderline (BB)
- Borderline lepromatous leprosy (BL)
- Lepromatous leprosy (LL)
- Indeterminate leprosy (I)
Depending on the form of leprosy and the body’s immune response, symptoms can vary widely. For example, people with the tuberculoid form of leprosy usually have a strong immune response and few bacteria, leading to well-marked skin lesions with reduced feeling, while those with the lepromatous type have a weaker immune response, many bacteria, and a broad range of symptoms.
The World Health Organization has also developed a classification system focusing on the number of lesions present. If five or fewer skin lesions are detected and tests show no bacteria, the disease is classified as paucibacillary (PB) leprosy. If one lesion is seen, it’s called single-lesion PB leprosy. If six or more lesions are present and a skin smear test is positive, it’s diagnosed as multibacillary (MB) leprosy.
Regardless of the type of leprosy, common symptoms include:
- Red skin patches with loss of sensation
- Feeling numbness and tingling in extremities
- Painless injuries to limbs
- Lumps or swelling on the earlobes
- Enlarged peripheral nerves
Other findings may include muscle weakness resulting in clawed fingers, facial paralysis, scanty eyebrows and eyelashes, and a perforated nasal septum. The severity of these manifestations depends on the degree of nerve involvement, the type of leprosy, and the degree of active immune response.
Along with the skin lesions, nerve damage, commonly found in leprosy, leads to reduced sensation, or, in some cases, pain. This nerve impairment can involve several nerve trunks including the ulnar, median, peroneal, posterior tibial and facial nerves.
In addition to the physical symptoms, people with leprosy can also experience systemic reactions known as leprosy reactions. These reactions can occur before treatment, during treatment, or even after treatment has ended. The two main types of leprosy reactions are T1R and T2R. Both reactions can cause symptoms like fatigue, fever, nerve injury, arthritis, neuritis, and nasopharyngeal symptoms.
Early diagnosis and prompt treatment are critical in managing leprosy and preventing complications that could lead to disability. Comprehensive medical evaluations including skin examinations and nerve function tests are essential for accurate diagnosis and effective management of the disease.
Testing for Leprosy (Hansen Disease)
When testing for leprosy, labs commonly use skin biopsies and a technique called polymerase chain reaction (PCR). They look for certain signs in your blood, like higher than normal white blood cell count, lower than normal hemoglobin and hematocrit, heightened liver function tests, and higher levels of a protein called C-reactive protein.
A skin biopsy involves taking a small sample of your skin to examine it under a microscope. It’s important to include not just the skin but the tissues just beneath it. This lets doctors see the impact of the disease on your nerves and gauge the severity of your skin lesions. The biopsy can show different types of cells that indicate the kind of leprosy a person has. Please note, doctors also try to rule out other skin infections that might affect the results.
PCR is another lab technique used to detect DNA of the bacteria that cause leprosy in your skin tissue. PCR is great for detecting the bacteria but doesn’t do as well at identifying what type it is. It is very accurate: in some studies, PCR detected the bacteria in over 90 percent of samples, and confirmed it wasn’t present in 100 percent of the samples where it was truly absent.
Another kind of test involves injecting a dead version of the bacteria into your skin and checking for a reaction after 3 to 4 weeks. If you test positive, it does not mean you have leprosy, but that you’ve been exposed to it. Interestingly, in areas where leprosy is common, up to 70 percent of people without the disease tested positive, while only 15 to 50 percent of confirmed leprosy patients did.
Lastly, serology tests are used in some places, although they’re not common practice in the U.S. They test your blood for a response to a specific component of the leprosy bacteria. However, it’s not always reliable because it can give false-positive results, and it doesn’t work well for all types of leprosy.
Treatment Options for Leprosy (Hansen Disease)
Leprosy, a disease caused by bacteria called M. leprae and M. lepromatosis, is typically treated with multiple drug therapy (MDT). This treatment is very effective at killing the bacteria and preventing it from spreading, drastically reducing the risk of the disease becoming resistant to medicine. A combination of medications, including dapsone, rifampin, and clofazimine, has proven to be the most efficient for this treatment.
Historically, leprosy was first treated with a drug called promine, a sulfone. Yet, after using this drug alone for a while, the bacteria developed resistance. That’s when multiple drug therapy was introduced. In 1982, the World Health Organization recommended using both dapsone and rifampin for a less severe form of leprosy (called tuberculoid leprosy), and adding clofazimine for a more serious form (called lepromatous leprosy).
New guidelines from the World Health Organization in 2018 suggest that all individuals with leprosy, regardless of the severity, should receive the combination of rifampin, dapsone, and clofazimine. This change was to prevent the undersupply of medication to patients with more severe leprosy who were misclassified as having a less severe form.
Once someone starts treatment for leprosy, the typical skin redness and hardness begin to soften after a few months, but it can take years for skin symptoms to fully clear up. The rate at which the killed bacteria are removed from the body is slow, but eventually, complete resolution of symptoms is very likely.
Leprosy can also cause inflammatory reactions that can happen before, during, or even months to years after the completion of the treatment. This can cause symptoms like fatigue, fever, joint pain, and nerve damage, leading to paralysis and deformity. Severe cases with this kind of reactions are treated with prednisone and other corticosteroids (anti-inflammatory drugs) to prevent irreversible nerve damage.
People with reactions that can’t be controlled with corticosteroids can be treated with cyclosporine. Severe type 2 reactions are often treated with prednisone and clofazimine. And in cases where these drugs are not effective, thalidomide is used, which is particularly effective for type 2 reactions. However, since thalidomide often causes birth defects, it’s not recommended for women who are or may become pregnant.
There’s also some emerging research looking into the use of cytokines (proteins that regulate immunity) for treating leprosy, but these aren’t widely used yet.
What else can Leprosy (Hansen Disease) be?
If doctors suspect someone has leprosy, a key sign is if the person can’t feel light touch or a pin-prick in the affected area. To confirm their diagnosis, a skin biopsy is usually taken. The doctors also have to consider other diseases that can look like leprosy. These diseases include:
- Granuloma annulare: This disease appears as a bump-free red plaque with bumps around the edge that often looks like a rope. The center usually clears up. Bumps can be seen on the wrists, hands, feet, and ankles.
- Fungal infection: Starts as a red, round, scaly patch that spreads outward and clears up in the center. The edges are raised and red. A potassium hydroxide preparation test can confirm the diagnosis.
- Annular psoriasis: Not a common type of psoriasis, but can sometimes occur. Diagnosed by the increasing occurrence of psoriasis symptoms, like classic plaques or nail disease. A biopsy can confirm it.
- Systemic lupus erythematosus: Can cause skin rashes on the face (butterfly rash) or all over the body. Also, rashes can appear on the skin after it has been exposed to sunlight.
- Keloid: A keloid is a raised scar that grows bigger than the original wound and can spread to the skin next to the wound.
- Mycosis fungoides: This disease can cause patches, tumors, redness all over the skin, and hair loss. A biopsy of the skin can confirm the diagnosis.
- Neurofibromatosis: Dominant symptoms include brown spots on the skin (café-au-lait macules), freckles in the armpits and groin, and nerve tumors (neurofibromas). The diagnosis is based on these symptoms.
- Cutaneous leishmaniasis: Lesions usually occur on exposed skin areas and start as pink bumps. These bumps grow into nodules and later ulcerate, harden, and are not painful.
During type 1 reactions, diagnosis is usually based on the doctor’s examination. Lab tests are not typically helpful in these cases. Even though high levels of chemokine CXCL10 have been found to be associated with type 1 reactions, CXCL10 should not be used as a marker for diagnosing these reactions. This is because it is not usually found in high levels before the reaction occurs and therefore isn’t a reliable predictor.
What to expect with Leprosy (Hansen Disease)
The outcome of leprosy, a long-term infection mainly causing skin sores and nerve damage, greatly depends on several factors. These include the stage of the disease when diagnosed, how quickly treatment begins, the patient’s access to the treatment, and whether the patient consistently follows the treatment plan.
By starting multidrug therapy (MDT), a combination of medicines, soon after the first signs of leprosy, it’s generally seen as a disease that can be cured. This treatment can help stop severe physical changes and nerve damage from happening. Following the treatment plan correctly can limit the amount of nerve damage that occurs. However, some cases have shown that there’s little to no recovery from any muscle weakness or loss of feeling that happened before starting treatment.
After MDT is given, the chance of the disease coming back (relapse) after the treatment is completed is very low, and deaths from leprosy are rare.
Possible Complications When Diagnosed with Leprosy (Hansen Disease)
People with leprosy may develop nerve abscesses, especially on the ulnar nerve, which is the nerve on the inner side of the arm. Immediate surgery is needed to avoid irreversible damage. Nerve problems can also affect the eyes, causing cranial nerve palsies, corneal insensitivity, and inability to fully close the eyes. This can result in injuries, infections, cornea problems, and even blindness. Leprosy is a major cause of blindness in developing countries.
Leprosy can also lead to nerve damage in the limbs, making it hard to feel touch, pain, and heat, causing loss of fingers and toes. Although the exact reason is unknown, it could be due to poorly understood bone-decay process.
Inflammations or reactions related to the immune system can also occur in leprosy, posing severe health risks. Erythema nodosum leprosum (ENL), a skin condition featuring painful red lumps, is seen in about 50% of cases associated with a type of leprosy known as LL.
Beyond the primary effects on skin and peripheral nerves, leprosy can also impact the immune, endocrine, and blood-forming systems, as well as muscles, bones, and eyes.
Potential Complications:
- Nerve abscesses
- Cranial nerve palsies
- Corneal insensitivity
- Inability to fully close the eyes
- Nerve damage in the limbs
- Loss of fingers and toes
- Inflammations related to the immune system
- Effects on immune, endocrine, and blood systems
- Impacts on muscles, bones, and eyes
In terms of medication resistance, past research suggests that it hasn’t been a significant problem. However, a study conducted between 2009 and 2015 with more than 1900 patients showed some resistance to drugs: 3.8% with rifampin, 5.3% with dapsone, and 1.3% with ofloxacin. This suggests an increasing presence of drug-resistant strains of the bacteria causing leprosy.
Preventing Leprosy (Hansen Disease)
Controlling the spread of leprosy involves carefully managing the interactions of those who have the disease. Contact management includes treating people who are currently sick and monitoring those who have been in close contact with them. For example, family members living with a person who has leprosy should have regular check-ups at least once a year for five years. They should also be advised to seek immediate medical attention if they notice any signs of leprosy, such as changes in their skin or unusual feelings in their nerves.
The BCG vaccine, which is usually given to newborns, can provide some protection against leprosy. A single dose of the vaccine offers around 50% protection, while two doses can provide even greater protection. In places where many people have leprosy, this vaccine is usually given at birth.
The World Health Organization (WHO) also suggests giving a single dose of a drug called rifampin to children over two years of age and adults in areas where leprosy is common. This is thought to help prevent leprosy, and research is currently underway to confirm this.
It’s also crucial to educate people about leprosy, including what it is, how it’s treated, what to expect in terms of recovery and any potential complications. It’s also important to tackle the social stigma associated with leprosy. Many cultures have negative views of this disease, which can make it harder for people to seek help and get the treatment they need.
