Alien Hand Syndrome

Caused by the separation of lobes in the brain, people suffering from this disorder essentially lose control of their hand as it seemingly takes on a mind of its own. While there is no known cure, giving the hand something to grasp will often be enough to keep it preoccupied.
Progeria

Wrinkles, baldness, missing teeth…stick around long enough, and you’re sure to have your fill. While old age happens eventually, to children affected by Progeria, all of those symptoms manifest themselves before the age of two. Although mentally they are still their age, many of these children develop the illnesses typically associated with the elderly, such as cardiovascular disease and arthritis. Rarely do they live to be older than 12 or 13.
Human Werewolf Syndrome

Sure, you may have some hairy friends, but not like this. Formally known as hypertrichosis, there are only about 50 people in the world afflicted with this rare disorder. Unfortunately for them, not even laser hair removal is an effective treatment as the hair will rapidly grow back.
Stone Man Syndrome

More formally known as Fibrodysplasia Ossificans Progressiva, this extremely rare mutation of the body’s repair mechanism often causes injured muscles, tendons, and ligaments to be ossified, or turned to bone. In fact, as the name suggests, within decades, a person can be rendered completely immobile.
Alice in Wonderland Syndrome

Probably as a result of something malfunctioning in the brain’s occipital lobe, this disorder causes people to percieve objects as being either much larger or smaller than they really are. Moreover, the individual will also mispercieve the passage of time and possibly have their sense of hearing and touch affected as well.