Hypertrichosis is a rare genetic condition that results in extreme hairiness. It is sometimes referred to as “werewolf syndrome”. Only about 50 cases in history have been documented. There is some speculation that Esau, son of Isaac and twin brother of Jacob, may have had hypertrichosis. He was described in the Old Testament as born covered in red hair, and was referred to as a hairy man by his brother as an adult. Here are several more cases.