Mycobacterium leprae causes leprosy, also known as Hansen’s disease.
Leprosy is a chronic infectious disease that primarily targets the skin and peripheral nerves, but it can also affect the eyes, nose, and muscles. Damage to sensory nerves can cause numbness and weakness, which is why untreated disease may lead to unnoticed injuries, deformity, and disability. The illness usually develops slowly, often over years rather than days or weeks.
M. leprae is an acid-fast, rod-shaped bacterium and an obligate intracellular parasite. Unlike many bacteria, it cannot be grown in ordinary cell-free laboratory culture, reflecting its dependence on host cells. The organism was identified by Norwegian physician Gerhard Armauer Hansen in 1873, making it one of the earliest bacteria linked to a human disease.
A common misconception is that leprosy is extremely contagious or untreatable. In reality, prolonged close contact is generally required for transmission, and modern multidrug therapy can cure the infection. Mycobacterium lepromatosis is another species known to cause Hansen’s disease, but M. leprae remains the classic and canonical answer to this quiz question.