— What is leprosy, which pathogen causes it, and how long has it been known?
— Leprosy is caused by two closely related bacteria, Mycobacterium leprae and Mycobacterium lepromatosis. It has a long incubation period and can present with a wide range of granulomatous lesions affecting the skin, the mucous membranes of the upper respiratory tract, the peripheral nervous system, bones and joints, and, in some cases, the eyes. Early signs might be subtle, and symptoms can evolve over years.
Leprosy is a disease with ancient roots. Records trace its existence back thousands of years, with some of the earliest descriptions appearing in early civilizations. It is believed to have originated in Asia or Africa and to have reached Europe around the time of classical antiquity. In the Middle Ages, Europe saw higher rates in certain regions, similar to patterns seen in other parts of the world.
— In which year was the causative agent of leprosy discovered and what is it? What organisms can live and reproduce?
— In 1873, the Norwegian physician Gerhard Armauer Hansen identified the bacterium responsible for leprosy, establishing that the disease is caused by Mycobacterium leprae. For many years it was thought that M. leprae was the sole cause, but later studies showed that M. lepromatosis can also cause leprosy in humans. The main reservoir and source of the bacteria is humans. Among animals, the nine-banded armadillo (Dasypus novemcinctus) in the Americas is the only proven natural host and reservoir for M. leprae.
— How is leprosy transmitted? Do people get sick from swimming in a pool or from contact with animals?
— Transmission occurs mainly through close, prolonged contact with an untreated person, as bacteria shed from the nose and throat can be released in droplets during sneezing or coughing. Less commonly, damaged skin can facilitate transmission. There is also some evidence that the disease can pass from mother to fetus through breast milk or blood, though this is not the typical route. Animals such as armadillos can serve as reservoirs, and people who handle or consume these animals may become infected, though the overall risk for most people is low.
— How long is the incubation period? Are there people who live with sick individuals and do not become ill? What explains resistance to leprosy?
— Leprosy has a lengthy incubation period, often extending for years or even decades after infection before symptoms appear. Many people who live with someone who has leprosy never develop the disease, a reality linked to variations in individual immune responses and genetic factors that influence susceptibility.
— What are the symptoms of leprosy, how can someone suspect they have it, and what tests confirm the diagnosis?
— Early signs are diverse and may be nonspecific. They can include reddish or pale patches on the skin, sometimes accompanied by numbness, tingling, or weakness. Additional clues include facial changes, thickened or tender nerves, and sensory loss within lesions. Diagnosis is typically confirmed by detecting the bacteria in skin samples or nasal scrapings, or by histological examination of skin biopsies from affected areas.
— Why do skin spots become insensitive to pain and touch?
— The bacteria invade sensory nerves in the skin, disrupting their ability to sense pain, temperature, and touch, which leads to reduced or lost sensation in the affected areas.
— Does leprosy cause impotence? Does this occur in every patient?
— Available data indicate that sexual health can be affected in some individuals with leprosy due to hormonal changes and inflammation. Reported effects on libido and testicular function vary and are not universal among patients.
— How exactly does bone and cartilage change occur in leprosy?
— Long-term infection can lead to changes in bone tissue, especially in the distal limbs. Inflammation may cause bone loss, thinning of bones, and structural alterations. Neurotrophic complications can contribute to deformities, which are sometimes described as characteristic patterns affecting the fingers and limbs. Periosteal and soft tissue changes may accompany these bone alterations, leading to functional impairment in advanced cases.
— How many patients are treated in Russia? Are there leprosy colonies, and how many exist?
— Leprosy has persisted sporadically in some regions of Russia. With improved home health care, the number of registered cases has declined over recent decades, though new cases have appeared in recent years, concentrated in certain areas. Treatment settings have shifted away from segregated colonies toward integrated care within general health services. A few specialized facilities and centers exist to support diagnosis and management.
— How are these patients treated now?
— The shift from isolation to treatment began with the advent of sulfone drugs in the mid-20th century. Multidrug therapy regimens have since become standard to prevent resistance and achieve cure. Current practice generally includes combinations of antibiotics tailored to regional guidelines, with ongoing monitoring for adverse effects and response. In some places, certain drugs may not be registered locally, requiring adaptation under national health authority protocols.
— Is there drug resistance to these medicines?
— Resistance can occur, requiring alternative medications or regimens under medical supervision. In such cases, clinicians may turn to other antibiotic classes and supportive therapies, including physical rehabilitation and pain management as part of comprehensive care.
— Are scientific studies conducted to explore new treatments for leprosy?
— Ongoing research in many countries aims to improve diagnosis, shorten treatment courses, and reduce side effects. Some centers have developed diagnostic tests to detect bacterial DNA in humans, with regulatory approval processes underway in certain jurisdictions. Scientists continue to evaluate locally produced medicines and innovative approaches to enhance patient outcomes while aligning with international treatment guidelines.