Dystrophy is wastage of tissue, usually muscles. Sudeck’s dystrophy mainly affects wrists or ankles, or another part of the arm or leg. The cause is unknown, but is probably a disorder of the autonomic nervous system. Usually this is a reaction of the nervous system to an (often minor) injury to an arm or leg. For this reason it is sometimes also called reflex dystrophy. First, dilation of the veins causes red and swollen skin. The skin is very sensitive. In the next phase the skin is shiny, and hair begins to fall out, and the veins begin to become constricted. Finally severe venous constriction causes nutritional deficiency in all tissue. Muscles become thinner, bones show osteoporosis, which makes them more brittle. Joint tissue in the affected area also wastes, causing restricted movement. Movement is further restricted by the formation of connective tissue in muscles, followed by contractures. Treatment is by resting the affected part of the body, combined with painkillers, corticosteroids and dilatory medication. At a later stage physiotherapy restores or maintains mobility. If necessary affected nerve fibres can be cut by surgery, a so-called sympathectomy. With correct and early treatment the condition can be cured almost completely.