Nerve involvement in leprosy. Pathology, differential diagnosis and principles of management

Abstract

Nerve damage in nonlepromatous leprosy and in 'reversal' reactions is the result of an immune response to the presence of antigenic material derived from leprosy bacilli within nerves. This immune response damages nerves by intraneural epithelioid cell formation, and by compression of Schwann cells due to inflammatory edema. In lepromatous leprosy the presence of leprosy bacilli induces slow damage to both perineurium and Schwann cells. When Erythema Nodosum Leprosum (ENL) develops, associated neuritis is probably brought about by the presence of ENL lesions within the nerves. In the absence of typical skin lesions, the nerve damage caused by leprosy can mimic other conditions. The differential diagnosis in such cases is outlined, and the principles of management of nerve damage due to leprosy are summarised.