Editing Hypertrichosis (section)

== Classification ==
Two methods of classification are used for hypertrichosis.<ref name="diseasesoftheskin" />  One divides them into either generalized versus localized hypertrichosis, while the other divides them into congenital versus acquired.<ref name="PMID12582385" /><ref name=Book08 />

=== Congenital ===
Congenital forms of hypertrichosis are caused by genetic mutations, and are extremely rare, unlike acquired forms.<ref name="diseasesoftheskin" /> Congenital hypertrichosis is always present at birth.<ref name="dermnet" />

;Hypertrichosis lanuginosa
:Congenital hypertrichosis lanuginosa can be noticed at birth, with the infant completely covered in thin [[lanugo]] hair.<ref name="dermnet" /> In normal circumstances, lanugo hair is shed before birth and replaced by [[vellus]] hair; however, in a person with congenital hypertrichosis lanuginosa, the lanugo hair remains after birth.<ref name="dermnet" /> The palms of the hands, soles of the feet, and mucous membranes are not affected.<ref name="PMID12582385" /> As the person ages, the lanugo hair may thin, leaving only limited areas of hypertrichosis.<ref name="congenitallanuginosa" />
;Generalized hypertrichosis
:Congenital generalized hypertrichosis causes males to exhibit excessive facial and upper body hair, whereas women exhibit less severe asymmetrical hair distribution.<ref name="PMID7663516" /> The palms, soles, and mucous membranes are not affected.<ref name="PMID12582385" />
;Terminal hypertrichosis
:Congenital terminal hypertrichosis is characterized by the presence of fully pigmented [[terminal hair]] that covers the entire body.<ref name="dermnet" /> This condition is usually accompanied by [[gingival hyperplasia]].<ref name="dermnet" /> This form is most responsible for the term "werewolf syndrome" because of the thick, dark hair that appears.<ref name="dermnet" /> People with this condition are sometimes performers at circuses because of their unusual appearance.<ref name="dermnet" />
;Circumscribed hypertrichosis
:Congenital circumscribed hypertrichosis is associated with the presence of thick [[vellus hair]] on the upper extremities.<ref name="PMID8844750" /> Circumscribed signifies this type of hypertrichosis is restricted to certain parts of the body, in this case, the extensor surfaces of the upper extremities.<ref name="PMID8844750" /> Hairy elbow syndrome, a type of congenital circumscribed hypertrichosis, shows excessive growth on and around the elbows.<ref name="PMID8844750" />  This type of hypertrichosis is present at birth, becomes more prominent during aging, and regresses at [[puberty]].<ref name="PMID8844750" />
;Localized hypertrichosis
:Congenital localized hypertrichosis is a localized increase in hair density and length.<ref name="diseasesoftheskin" />
;Nevoid hypertrichosis
:Nevoid hypertrichosis may be present at birth or appear later in life.<ref name="dermnet" /> It features an isolated area of excessive terminal hair and is usually not related to any other diseases.<ref name="dermnet" /><ref name="PMID9198325" />

=== Acquired ===
Acquired hypertrichosis appears after birth. The multiple causes include the side effects of drugs, associations with cancer, and possible links with eating disorders. Acquired forms can usually be reduced with various treatments.

;Hypertrichosis lanuginosa
:Acquired hypertrichosis lanuginosa is characterized by rapid growth of lanugo hair, particularly on the face.<ref name="acquiredlanugo2" /><ref name="hypertrichosislanuginosaacquisita" /> Hair also appears on the trunk and armpits, while palms and soles are unaffected.<ref name="hypertrichosislanuginosaacquisita" /> The excess hair is commonly referred to as malignant down.<ref name="hypertrichosislanuginosaacquisita" /> This hair is very fine and unpigmented.<ref name="hypertrichosislanuginosaacquisita" />
;Generalized hypertrichosis
:Acquired generalized hypertrichosis commonly affects the cheeks, upper lip, and chin.<ref name="dermnet" /><ref name="diseasesoftheskin" />  This form also affects the forearms and legs, but is less common in these areas. Another deformity associated with acquired generalized hypertrichosis is multiple hairs occupying the same follicle. It may also include abnormal hair growth patterns as what happens to the eyelashes in a condition known as [[trichiasis]].<ref name="diseasesoftheskin" /> Oral [[minoxidil]] treatments for [[hypertension]] are known to cause this condition. Topical minoxidil used for [[alopecia]] causes hair growth in the areas where it is applied; however, this hair disappears shortly after discontinuing the use of topical minoxidil.<ref name="minoxidil" />
;Patterned hypertrichosis
:Acquired patterned hypertrichosis is an increase in hair growth in a pattern formation. It is similar to acquired generalized hypertrichosis and is a sign of internal [[malignancy]].<ref name="Andrews" />
;Localized hypertrichosis
:Acquired localized hypertrichosis is an increase in hair density and length often secondary to irritation or trauma.<ref name="Fitz2" /> This form is restricted to certain areas of the body.

=== Hirsutism ===

{{Main|Hirsutism}}
Hypertrichosis is often mistakenly classified as hirsutism.<ref name="PMID12582385" /> Hirsutism is a type of hypertrichosis exclusive to women and children, resulting from an excess of [[androgen]]-sensitive hair growth.<ref name="hirsutism" /> Patients with hirsutism exhibit patterns of adult male hair growth.<ref name="PMID12582385" /> Chest and back hair are often present on women with hirsutism.<ref name="hirsutism" />

Hirsutism is both congenital and acquired. It is linked to excessive male hormones in women, thus symptoms may include acne, deepening of the voice, irregular menstrual periods, and the formation of a more masculine body shape.<ref name="hirsutism" /> Increases in androgen (male hormone) levels are the primary cause of most hirsutism cases.<ref name="PMID18081798" /> If caused by increased levels of androgens, it can be treated with medications that reduce androgen levels. Some birth control pills and [[spironolactone]] reduce androgen levels.<ref name="hirsutism" />