Conditions in which symptoms and signs are due to an abnormally functioning AUTONOMIC NERVOUS SYSTEM. The most researched of these is familial dysautonomia, a genetic disorder primarily of Ashkenazi Jews (those of East European Origin) of whom 1 in 30 carries the affected abnormal gene. The children have difficulty sucking and swallowing from birth, are ‘floppy’ and delayed in growth and development. Their body temperature can vary markedly throughout the day and they have wide swings in blood pressure. They may be insensitive to pain. Another, less well understood form of dysautonomia is POTS – postural orthostatic tachycardia syndrome which mostly affects young women and results in episodes of rapid pulse rate, fainting, chest pain, shortness of breath and intolerance of exercise with abnormal sensitivity to temperature change. There is also a rare degenerative and ultimately fatal disorder, multiple system atrophy, which has certain similarities to PARKINSONISM.