The prefix hyper means excessive or abnormal, while trichosis is the name for a condition that affects hair growth. Hypertrichosis, therefore, refers to excessive hair growth. It is sometimes referred to as Werewolf syndrome. The exact causes of the condition aren't known.
Hypertrichosis is a rare disorder that can affect men or women. People may experience abnormal hair growth all over the body, or the condition may affect smaller patches. It may be present from birth or can affect people later on in life. Most hypertrichosis symptoms relate to patterns of hair growth.1‘Hypertrichosis.’ DermNet NZ , dermnetnz.org/topics/hypertrichosis/
Fine Body Hair
Some people with hypertrichosis have soft, fine hairs growing all over the body. These hairs are known as lanugo. They have no pigment and are typically a few centimeters long.
Lanugo covers a fetus but is usually shed shortly before birth and replaced by a different type of hair, known as vellus hair. Vellus hair is generally shorter than lanugo hair. In a rare condition called congenital hypertrichosis lanuginosa, a person is born covered in these silky lanugos. The fine down-like hairs remain throughout the person's whole life.2Saleh, Dahlia, et al. ‘Hypertrichosis.’ StatPearls, StatPearls Publishing, 5 January 2021