Which are the causes of Leprosy?

Leprosy, also known as Hansen’s disease, is caused by a chronic infection with the slow-growing bacteria Mycobacterium leprae or Mycobacterium lepromatosis. While these bacteria are the direct cause, most individuals possess a natural immunity that prevents infection, meaning the disease is not highly contagious through casual contact.

What causes Leprosy to develop?

The primary cause of Leprosy is the invasion of the skin, peripheral nerves, and upper respiratory tract by M. leprae. Unlike many other infections, Leprosy requires prolonged, close contact with untreated individuals over many months. The bacteria multiply very slowly, often leading to an incubation period that can last from five to twenty years before symptoms appear.

Are there genetic factors linked to Leprosy?

While Leprosy is not a genetic disease, clinical research indicates that host genetics play a significant role in susceptibility. Studies have identified specific genetic variations, particularly in the HLA (Human Leukocyte Antigen) region and genes involved in the innate immune response (such as NOD2), that influence how a person’s body recognizes and fights the bacteria. These genetic factors explain why only about 5% of people exposed to the bacteria actually develop clinical Leprosy.

What are the risk factors for Leprosy?

There is a critical distinction between the cause (the bacteria) and risk factors (conditions that make infection more likely). Key risk factors include:

• Living in regions where Leprosy is endemic (e.g., parts of India, Brazil, and Indonesia).


• Prolonged household contact with an untreated person who has multibacillary Leprosy.


• Compromised immune system function, which may reduce the body's ability to clear the bacteria.


• Living in conditions of overcrowding or poor sanitation, which may facilitate transmission.

What is the current status of research into Leprosy?

Current research is focused on the mechanisms of nerve damage and the development of more sensitive diagnostic tests, such as PCR-based assays to detect bacterial DNA. Scientists are also investigating the role of the environment and zoonotic transmission, specifically the role of armadillos as natural reservoirs for M. leprae in certain regions.

Next steps

• Consult an infectious disease specialist if you suspect symptoms like persistent skin lesions or numbness.


• Visit the World Health Organization (WHO) or NIH GARD portals for updated clinical guidelines.


• Connect with the DiseaseMaps.org community to share experiences and find local support resources.

Medical disclaimer: This content is for informational purposes only and does not constitute professional medical advice, diagnosis, or treatment; always seek the advice of your physician regarding any medical condition.

References

• NIH Genetic and Rare Diseases Information Center (GARD) - Leprosy


• World Health Organization (WHO) - Leprosy (Hansen's disease) Fact Sheets


• Orphanet - Leprosy


• Centers for Disease Control and Prevention (CDC) - Hansen's Disease (Leprosy)