Leprosy is caused by the bacteria Mycobacterium leprae, which damages the skin and nerves slowly over many years. It results in skin lesions and deformities that typically affect the cooler areas of the body. The disease is transmitted through prolonged skin contact with infected individuals or droplets from their nasal secretions. Diagnosis involves identifying characteristic skin lesions and nerve thickening, along with detecting acid-fast bacteria in smears or biopsies. Treatment consists of multidrug regimens of antibiotics for 6-12 months depending on the classification of the disease.