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How can unnoticed injuries lead to deformities in people with leprosy?

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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.

In people with leprosy, deformities often arise as a secondary consequence of nerve damage rather than direct destruction by the bacteria themselves. The disease can cause an intense cellular reaction that spreads into nerve trunks, preventing the transmission of nerve impulses.1

This process leads to a loss of sensation, particularly in the extremities, meaning the patient becomes unable to feel pain, heat, or cold. Because these sensory signals are absent, minor injuries—such as cuts, burns, or scrapes—go unnoticed and untreated. Without the protective reflex of pain, these small wounds can develop into large, eroding ulcers. Over time, these chronic injuries can result in the loss of fingers and toes, or necessitate amputation if the limb condition becomes severe.1

While modern multidrug therapy is highly effective at killing the bacteria and halting disease progression, it cannot reverse tissue that has already been destroyed or permanently damaged.2