Final answer:
Leprosy, or Hansen's disease, primarily affects the 1) skin and nerves. It is caused by the bacterium Mycobacterium leprae and can lead to sensory loss and skin lesions, with severity depending on the individual's immune response.
Step-by-step explanation:
The two main areas of the body that are affected by leprosy, also known as Hansen's disease, are the skin and the nerves. Leprosy is caused by the bacterium Mycobacterium leprae, which attacks peripheral nerves leading to damage such as sensory loss. This loss of sensation can result in ulcers, deformities, and even the loss of fingers or toes. Additionally, the skin can present with blanched numb areas, which in severe cases, develop into lesions that can persist for years.
This disease's progression and its manifestations largely depend on the patient's immune response. An effective immune response containing the infection results in the less severe tuberculoid form, while an inability to contain the infection can lead to the more severe lepromatous form, characterized by extensive skin lesions and nerve damage. The bacillus primarily infects cooler regions of the body, such as the skin and the peripheral nerves in the extremities, and can survive within macrophages, a type of immune cell.