|Classification and external resources|
Hypertrichosis can be stated simply as unnatural and excessive growth of hair on the body. Hypertrichosis can occur over the entire body, or may be isolated to a certain area. It may be congenital, present at birth, or acquired, arising later in life.
- Congenital Hypertrichosis Lanuginosa
Congenital hypertrichosis lanuginosa is a rare form of hypertrichosis first noticeable at birth, as the infant is completely covered with thin lanugo hair. Normally, lanugo hair is shed before the infant is born and is replaced by vellus hair; however in persons suffering from congenital hypertrichosis lanuginosa, the lanugo hair is never shed, and instead persists throughout the life of the individual. Hypertrichosis lanuginosa congenita is a dominant autosomal cutaneous disorder, meaning it is a dominant trait, not related to the sex chromosome, that affects the skin.
- Congenital Generalized Hypertrichosis
Congenital generalized hypertrichosis is a dominant trait which has been linked to the X chromosome. In males, excessive facial and upper body hair are apparent, while women typically exhibit asymmetrical hair distribution.
- Congenital Hypertrichosis Terminalis
Congenital hypertrichosis terminalis is characterized by the presence of terminal hair which covers the entire body. This condition almost always presents with gingival hyperplasia. This form is most responsible for the term "Werewolf Syndrome" because of the thick dark hair that appears. Sufferers of this condition are usually performers at circuses because of their unnatural appearance.
- Congenital Circumscribed Hypertrichosis
Congenital circumscribed hypertrichosis is closely associated with the presence of thick vellus hair on the upper extremities. Circumscribed signifies that this type of hypertrichosis is restricted to certain parts of the body, in this case, the upper extremities. Hairy Elbow Syndrome, a type of congenital circumscribed hypertrichosis, shows excessive growth on and around the elbows. This type of hypertrichosis is present at birth and becomes more prominent during aging, only to regress at puberty.
- Localized Congenital Hypertrichosis
- Acquired Generalized Hypertrichosis
Acquired generalized hypertrichosis is a type that is gained, after birth, due to some underlying cause. This type of hypertrichosis can usually be reduced with various treatments. This form also does not usually affect the whole body. The most common areas affected is all over the face including cheeks, upper lip, and chin. Less commonly, this form also affects the forearms and legs. Another deformity that may come with this form is multiple hairs occupying the same follicle or hairs going off of their normal growth paths as what happens to the eyelashes in a condition known as trichiasis.
- Patterned Acquired Hypertrichosis
- Localized Acquired Hypertrichosis
- Naevoid Hypertrichosis
Naevoid hypertrichosis may be congenital or acquired because it can appear at birth or later in life. It features a lone excessively hairy area on the body and is usually not related to any other diseases.
- Are these the only types?
All types of congenital hypertrichosis are caused by some sort genetic mutation, and are present at birth. Congenital hypertrichosis languniosa is inherited through a gene, hence the name congenital. The exact mutation of the gene is unknown. When it comes to acquired generalized hypertrichosis, there are a wide range of possible causes that are not fully proven; however, there are some factors that scientists think to be possible causes of hypertrichosis. Hypertrichosis may become present as a side effect of a drug. This is, in fact, the most common form of hypertrichosis. It can often be present in children. Minoxidil, a medication for preventing hair loss, is known to cause hypertrichosis. Medication induced hypertrichosis can often be solved by using hair removal agents such as a calcium thioglycolate depilatory agent. Another cause that is believed to contribute to hypertrichosis is irritation following immediate increased blood in the area that is to be affected . Acquired generalized hypertrichosis can be obtained through cancer. The hair that grows is known as malignant down and is fine and silky. Scientists are unsure of why cancer causes hypertrichosis at this point. Other possible causes of acquired hypertrichosis include, metabolic disorders, anorexia, and drugs or chemicals such as oral phentynoin and ciclosporin.
Hypertrichosis occurs once in every ten billion people. Today, only about 20 people suffer from the condition.
People suffering from hypertrichosis usually found jobs as circus performers due to their unnatural appearance. Fedor Jeftichew, the dog boy, Stephan Bibrowski, the lion faced man, Jesus "Chuy" Aceves, wolf boy, and Annie Jones, the bearded woman, are all notable sufferers of hypertrichosis." 
The hypertrichosis condition has been linked to the X chromosome. A female carrying the hypertrichosis gene has a 50-50 chance of passing it to her offspring. A male carrying the gene will always pass it onto his daughters, but never to his sons. The gene that causes hypertrichosis is believed to be from the time when primates were evolving to men.
There is no cure for hypertrichosis, but most of it is only cosmetic, and hair removal can reduce the appearance of it. Treatment can also have adverse effects by causing scarring, dermatitis, and hypersensitivity.
- Sutton, Richard L. (1916). Diseases of the Skin. C.V. Mosby Company. pp. 408,705.
- Baird, Elizabeth; Strack, Mathew (June 15), Hypertrichosis, retrieved September 20, 2009 Check date values in:
|date=, |year= / |date= mismatch(help)
- Mendiratta, Vibhu; Harjai, Bhawna; Gupta, Tanvi (2008), Pediatric Dermatology, 25 (4 ed.), Lady Hardinge Medical College, Associated Shrimati Sucheta Kriplani and Kalawati Saran Childrens Hospital, New Delhi, India: Wiley Periodicals, Inc., doi:10.1111/j.1525-1470.2008.00716.x
- Macías-Flores, MA; García-Cruz; Rivera; Escobar-Luján; Melendrez-Vega; Rivas-Campos; Rodríguez-Collazo; Moreno-Arellano; Cantú (1984). "A New Form of Hypertrichosis Inherited as an X-linked Dominant Trait". Human genetics. 66 (1): 66–70. PMID 6698556.
- Figuera, L.; Pandolfo, M.; Dunne, P.; Cantú, J.; Patel, P. (1995). "Mapping of the congenital generalized hypertrichosis locus to chromosome Xq24-q27.1". Nature genetics. 10 (2): 202–207. PMID 7663516. doi:10.1038/ng0695-202.
- Escalonilla, P; Aguilar; Gallego; Piqué; Fariña; Requena (1996). "A new case of hairy elbows syndrome (Hypertrichosis cubiti)". Pediatric dermatology. 13 (4): 303–5. PMID 8844750.
- Earhart, RN; Ball; Nuss; Aeling (1977). "Minoxidil-induced hypertrichosis: treatment with calcium thioglycolate depilatory". Southern medical journal. 70 (4): 442–3. PMID 850811.
- Hall, Dave (2007), Doctor Doctor..., retrieved October 23, 2009
- ABC News (August 2), Hypertrichosis - Real Life Werewolves?, retrieved September 20, 2009 Check date values in:
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