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Why can leprosy cause a loss of sensation?

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Sign reading Gandhiji Prem Nivas Leprosy Centre Titagarh conducted by Missionaries of Charity, with a crucifix above the sign on a decorated building facade. — leprosy The Gandhiji Prem Nivas is a center for people with leprosy that was established by Mother Teresa in 1958 and is run by the Missionaries of Charity in Titagarh, India.

Leprosy causes a loss of sensation primarily because the leprosy bacillus (Mycobacterium leprae) damages the peripheral nerves.

In the tuberculoid form of the disease, the body mounts an intense cellular immune response that invades the skin and the nerve fibers ending within it. This inflammatory reaction spreads into the main trunks of the affected nerves, physically preventing the transmission of nerve impulses. Additionally, leprosy is associated with demyelinating neuropathies, where the insulating myelin sheaths of nerve fibers are affected, further blocking conduction.12

Because these nerves can no longer transmit signals, the infected person loses the ability to feel heat, cold, or touch in the affected areas. This lack of sensation is medically significant because it prevents the patient from feeling pain, often leading to unnoticed injuries, severe tissue degeneration, and potential deformity of the extremities.13