It's a condition of excess body hair. To a much worse level than you or I would worry about. It's believed that only 19 people living in the world (so about 1 in 340 million) currently have hypertrichosis. Most of them are part of one large extended Mexican family. Only about 50 people total in the World since the Middle Ages have been reliably reported to have the condition.

(Contrary to what you may have scene in an episode of CSI Las Vegas) the condition affects men much worse than women. Hypertrichosis results in fantastically excess body hair, either in just a localised area of the body, or nearly everywhere. In some cases, people with this condition really can look a bit like werewolves (minus all the wolf-like bits of anatomy, of course).

In nearly all cases the condition is believed ot have a genetic basis and there is no treatment. Metabolic and systemic disorders, as well as high exposure to certain drugs can produce similar symptoms, but these usually are treatable.