The pathology of human diabetic neuropathy.

Quantitative morphological data are presented from a series of studies assessing both nerve fiber and capillary pathology in 30 diabetic patients with varying stages and symptoms of neuropathy. There is a significant relationship between clinical measures of neuropathic severity and myelinated fiber loss. However, unmyelinated fibers continue to regenerate even in patients with established neuropathy. Microvascular abnormalities, particularly basement membrane thickening and endothelial cell hyperplasia, are an early feature of diabetic microangiopathy and relate to neuropathic severity. There are no neurophysiological or morphological differences between patients with type 1 and type 2 diabetes nor between diabetic patients with and without painful neuropathy.