Mycobacterium leprae is a slow-growing bacterium that causes leprosy, also known as Hansen's disease. It primarily affects the skin, nerves, and mucous membranes, leading to skin lesions and nerve damage. The bacterium is transmitted through prolonged close contact with an infected person, but it is not highly contagious. Leprosy has been known for centuries and is often associated with social stigma. Early diagnosis and treatment with antibiotics, such as dapsone, can effectively manage the disease and prevent complications. Public health efforts continue to focus on education and reducing the stigma surrounding leprosy to improve the lives of those affected.