Disorders of peripheral cutaneous nerves.

Area of Science:

• Neurology
• Immunology
• Infectious Diseases

Background:

• Leprosy's histopathology primarily affects peripheral cutaneous nerves.
• Mycobacterium leprae preferentially targets Schwann and perineurial cells.

Purpose of the Study:

• To describe the histopathology of leprosy, focusing on nerve damage.
• To elucidate the immune response and its consequences for peripheral nerves.

Main Methods:

• Histopathological examination of affected peripheral nerves.
• Analysis of the host-cell immune response to Mycobacterium leprae.

Main Results:

• Mycobacterium leprae are destroyed by a cell-mediated immune response, causing a 'dying-back' nerve phenomenon without neuroma formation.
• Sensory loss (anesthesia) and localized nerve trunk pain are primary symptoms, with rare paresthesiae.
• Peripheral nerves exhibit immunologic privilege for Mycobacterium leprae.

Conclusions:

• The immune response in leprosy leads to nerve degeneration rather than regeneration.
• Peripheral nerves serve as a sanctuary for Mycobacterium leprae due to localized immune privilege.