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'''Auricular hypertrichosis''' (''hypertrichosis lanuginosa acquisita'', ''hypertrichosis pinnae auris''), also known as '''hairy pinna''', is a genetic condition expressed as long and strong hairs growing from the [[Helix (ear)|helix]] of the [[Auricle (anatomy)|pinna]].<ref>{{cite book |last=Mader |first=Sylvia S. |year=2000 |title=Human biology |publisher=McGraw-Hill |___location=New York |isbn=978-0-07-290584-7 |oclc=41049448 |url-access=registration |url=https://archive.org/details/lccn_99014988 }}</ref>{{Page needed|date=June 2015}}
==Presentation==
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|url=http://www.medscape.com/viewarticle/407645 |title=Swimmer's Ear: An Ear Canal Infection |author=W. Steven Pray |publisher=U.S. Pharmacist |accessdate=31 August 2012}}</ref> In its broader sense, ''ear hair'' may also include the fine [[vellus hair]] covering much of the ear, particularly at the prominent parts of the anterior ear, or even the abnormal hair growth as seen in [[hypertrichosis]] and [[hirsutism]]. Medical research on the function of ear hair is currently very scarce.
Hair growth within the ear canal is often observed to increase in older men,<ref name="LeynerM.D.2005">{{cite book|last1=Leyner|first1=Mark|last2=M.D.|first2=Billy Goldberg|title=Why Do Men Have Nipples?: Hundreds of Questions You'd Only Ask a Doctor After Your Third Martini|url=https://books.google.com/books?id=MMSfSx1MDkcC&pg=PA206|accessdate=8 September 2014|date=2005-07-26|publisher=Crown Publishing Group|isbn=9780307337047|pages=206–}}</ref> together with increased growth of [[nose hair]].<ref>{{cite news|url=https://www.nytimes.com/2012/12/13/booming/nose-and-ear-hair-growth-in-baby-boomers.html?_r=0|title=Why Is Hair Growing Out of There?|last=Nagourney|first=Eric|date=December 13, 2012|work=[[The New York Times]]|accessdate=8 September 2014}}</ref> Excessive hair growth within or on the ear is known medically as ''auricular [[hypertrichosis]]''.<ref name="JacksonNesbitt2012">{{cite book|author1=Scott Jackson|author2=Lee T. Nesbitt|title=Differential Diagnosis for the Dermatologist|url=https://books.google.com/books?id=nvQruBczhccC&pg=PA125|date=25 April 2012|accessdate=24 October 2014|publisher=Springer Science & Business Media|isbn=978-3-642-28006-1|page=125}}</ref> Some men, particularly in the male population of India, have coarse hair growth along the lower portion of the helix, a condition referred to as "having ''hairy [[Auricle (anatomy)|pinnae]]''" (''hypertrichosis lanuginosa acquisita'').<ref>{{cite web|url=http://otoscopy.hawkelibrary.com/album05/6_15|title=Otoscopy: The Pinna|accessdate=26 October 2014|author=Hawke Library|archive-date=26 October 2014|archive-url=https://web.archive.org/web/20141026234127/http://otoscopy.hawkelibrary.com/album05/6_15|url-status=dead}}</ref>
==Genetics==
The genetic basis of auricular hypertrichosis has not been settled. Some researchers have proposed a Y-linked pattern of inheritance and others have suggested an autosomal gene is responsible. A third hypothesis predicts the [[phenotype]] results from the interaction of two loci, one on the homologous part of the X and Y and one on the nonhomologous sequence of the Y.<ref>{{cite journal | pmid = 14110028 | doi=10.1038/201424b0 | volume=201 | year=1964 | journal=Nature | pages=424–5 | last1 = Dronamraju | first1 = KR| title=Y-linkage in Man | issue=4917 | bibcode=1964Natur.201..424D | s2cid=4275336 }}</ref> These hypotheses are not mutually exclusive, and there may be a variety of genetic mechanisms underlying this phenotype.
Lee et al. (2004), using Y-chromosomal DNA binary-marker haplotyping, suggested that a cohort of southern Indian hairy-eared males carried Y chromosomes from many [[haplogroups|haplogroup]].<ref>{{cite journal | pmid = 15367914 | doi=10.1038/sj.ejhg.5201271 | volume=12 | title=Molecular evidence for absence of Y-linkage of the Hairy Ears trait | year=2004 | journal=Eur J Hum Genet | pages=1077–9 | last1 = Lee | first1 = AC | last2 = Kamalam | first2 = A | last3 = Adams | first3 = SM | last4 = Jobling | first4 = MA| issue=12 | doi-access = free }}</ref> The hypothesis of Y- linkage would require multiple independent mutations within a single [[population]]. No significant difference between the Y-haplogroup frequencies of hairy-eared males and those of a geographically matched control sample of unaffected males was established. The study concluded that auricular hypertrichosis is not Y-linked in southern India, though this result may not apply to all to all populations.<ref>{{cite journal | pmid = 4669458 | doi=10.1017/s1120962300010933 | volume=21 | title=Hypertrichosis of the ear rims. Two remarks on the two-gene hypothesis | year=1972 | journal=Acta Genet Med Gemellol (Roma) | pages=216–20 | last1 = Rao | first1 = DC| issue=3 | doi-access=free }}</ref>
== See also ==
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