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Congenital absence of pain perception is a rare phenotype. Here we report two unrelated adult individuals who have a previously unreported neuropathy consisting of congenital absence of pain with hyperhidrosis (CAPH). Both subjects had normal intelligence and productive lives despite failure to experience pain due to broken bones, severe cold or burns. Functional assessments revealed that both are generally hypesthetic with thresholds greater than two standard deviations above normal for a several of modalities in addition to noxious stimuli. Sweating was 3 to 8-fold greater than normal. Sural nerve biopsy showed that all types of myelinated and unmyelinated fibers were severely reduced. Extensive multi-antibody immunofluorescence analyses were conducted on several skin biopsies from the hands and back of one CAPH subject and two normal subjects. The CAPH subject had all normal types of immunochemically and morphologically distinct sensory and autonomic innervation to the vasculature and sweat glands, including a previously unknown cholinergic arterial innervation. Virtually all other types of normal cutaneous C, Adelta and Abeta-fiber endings were absent. This subject had no mutations in the genes SCN9A, SCN10A, SCN11A, NGFB, TRKA, NRTN and GFRA2. Our findings suggest three hypotheses: (1) that development or maintenance of sensory innervation to cutaneous vasculature and sweat glands may be under separate genetic control from that of all other cutaneous sensory innervation, (2) the latter innervation is preferentially vulnerable to some environmental factor, and (3) vascular and sweat gland afferents may contribute to conscious cutaneous perception.

(From Discover Magazine Online: http://discovermagazine.com/2010/apr/04-your-hidden-sense-of-touch)
You are more sensitive than you realize, neuroscientist Frank Rice of Albany Medical College has discovered. His study of patients whose skin lacks normal nerve fibers has revealed a previously unknown source of perception that contributes to the familiar ability to feel texture, temperature, pressure, and pain: the nerve endings surrounding blood vessels and sweat glands in human skin.

Rice, neurologist David Bowsher of the University of Liverpool, and their colleagues were studying two patients who were unable to feel pain, yet somehow retained a rudimentary ability to distinguish hot from cold and rough from smooth. On examining skin samples and other biopsies, the researchers found that all of the usual nerve endings associated with skin sensation were missing. The only possible sources of feeling were the nerves of the blood vessels and glands.

Scientists knew that such nerves existed but thought they simply regulated blood flow and perspiration. The evidence from the patients examined by Rice and Bowsher suggests that the nerve cells also act as an additional sensory system. “It is very likely that these nerve endings contribute to conscious perception in all of us,” Rice says. If he is correct, problems with this previously unknown system could contribute to poorly understood pain conditions, such as migraines and fibromyalgia. Rice and a group of collaborators are gearing up to investigate this potential link by searching for malformations of the blood-vessel nerves that could affect their function.