Prurigo nodularis. Histological and electron microscopical study.

We describe a typical case of prurigo nodularis, of 15 years' duration, in a middle-aged woman. Histological and electron microscopical examination of the skin lesions revealed distinct changes in the nerve tissue. There were groups of thickened nerve fibers that formed nodules with numerous Schwann cells. Some of the nerve bundles extended to the dermoepidermal junction. Electron microscopy showed very obvious lesions in the Schwann cells and axons. In the Schwann cells there was a lucent cytoplasm with few mitochondria, an absence of endoplasmic reticulum and a few irregular, membrane-bound vacuoles. While the mesaxons all appeared normal, the axons varied greatly in diameter; the small ones appeared normal and contained neurofibrils and neurotubules, whereas the large onew were empty. Every Schwann cell encircled a large number of axons. It may be assumed that the axon swelling is a nonspecific reaction to injury.