Korean J Dermatol.
1980 Feb;18(1):51-63.
Histopathological Studies of Peripheral Nerves in Leprosy
Abstract
- It is well known that leprosy bacilli have a special affinity for peripheral nerves, especially Schwann cells but also including perineurial cells and endothelial cells of endoneurial blood vessels. The Schwann cells, after invasion by and saturation with multiplied M. leprae, are destroyed and segmental demyelination and Wallerian degeneration follow. This condition, then is known to be the main neural pathogenosis in early leprosy. It is rarely observed that the progressive paralysis occurs in arrested leprosy patients under adequate treatment. Therefore, the authors performed a histopathologic study of 80 peripheral nerves obtained from the autopsies of 10 old lepromatous leprosy patients including two active cases whose disease durations ranged from 6 to 49 years. The authors arbitrarily divided all the histopathologic findings into 5 grades on the basis of 1) difference in pathological findings in relation to disease duration and bacterial index, and 2) the coexistence of various lesions within the same nerve trunk. As the disease progresses the destroyed nerve fibers are replaced by fibrous and granulation tissue while the perineurial reaction increases. The cellular reaction is minimal in the low grades. There is a slightly early increased vasculature probably due to M. leprae and later a more pronounced increase with large vessels indicating the presence of the granulation process. There is minimum to moderate interfascicular reaction throughout every grade, ie. increased cellularity, vessel wall thickening and increased numbers of vessels with fibrosis. Acid-fast bacilli were demonstrated only in the active cases. The coexistence of different fascicular lesions within the same nerve trunk of peripheral nerve and of femoral nerves mear the spinal cord indicates the presence of some perineurial inhibitory effect which, while promoting the centripetal spread of, prevents the transfascicular spread of M. leprae for some time.
