This is an extremely rare disorder first described by G. M Beard in 1878 and is believed to have been first observed in French Canadian Lumberjacks. Sufferers have a sudden and an abnormal reaction to stimuli. For example, when given a sudden command in a loud enough voice the individual will carry out that command instantly and without a thought, even if you tell them to hit out a loved one, or throw an object. Also, on hearing unfamiliar or foreign phrases they will often repeat them over and over again uncontrollably. Other symptoms include extreme jerky movements whenever a loud noise is heard, hence the "jumping" aspect to this disorder.
Walking Corpse Syndrome
People suffering from this condition may believe that they have lost parts of their bodies or even their souls and some might go as far as to really believe that they are already dead and are indeed a walking corpse, even maintaining that they can smell their own rotting flesh and can feel the worms eating at them. It has also been associated with psychosis linked to drugs such as amphetamines and cocaine and to schizophrenia.
Fish Odour Syndrome
A rare disorder where the body cannot produce a substance known as FM03 or monooxygenase 3 and as a result, its ability to break down Trimethylamine is impaired. The result of this is most unpleasant as it causes the person's sweat, urine and breath to give off a very strong and fishy odour or a smell like that of rotten eggs.
Alien Hand Syndrome
This unusual neurological disorder is where one hand appears to take on a personality all of its own and acts in such a way that is completely out of control in relation to what the person wants to do. For example the alien hand may unbutton shirts or remove clothing whilst the other hand is trying to button up or get dressed. Sufferers will often attach a personality to their alien hand and will try to punish it for disobedience.
People suffering from the extremely rare Capgras Syndrome believe that a loved one or a significant other person in their life is being impersonated by an impostor. This can even lead to the sufferer attacking the perceived impostor. Sometimes it extends itself to the sufferer themselves who believe that when they look in the mirror it is not their own reflection staring back at them but the image of an impersonator.