Auricular hypertrichosis (''hypertrichosis lanuginosa acquisita'', ''hypertrichosis pinnae auris'') is a genetic condition expressed as long and strong hairs growing from the

helix A helix (; ) is a shape like a cylindrical coil spring or the thread of a machine screw. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as the DNA molecule is for ...

of the pinna.

Presentation

Ear hair Ear hair is the terminal hair arising from hair follicle, folliculary cartilage inside the Ear canal, external auditory meatus in humans. In its broader sense, ''ear hair'' may also include the fine vellus hair covering much of the ear, particu ...

generally refers to the

terminal hair In humans, terminal hair is a variant of hair that is thick and long such as that growing on the scalp, as compared with vellus hair, colloquially known as peach fuzz, growing elsewhere.Marks, James G; Miller, Jeffery (2006)''Lookingbill and ...

arising from follicles inside the

external auditory meatus The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the auricle to the eardrum and is about in length and in diameter. Str ...

in humans. In its broader sense, ''ear hair'' may also include the fine

vellus hair Vellus hair is short, thin, light-colored, and barely noticeable hair that develops on most of a human's body during childhood. Exceptions include the lips, the back of the ear, the palm of the hand, the sole of the foot, some external genital ...

covering much of the ear, particularly at the prominent parts of the anterior ear, or even the abnormal hair growth as seen in

hypertrichosis Hypertrichosis (sometimes known as werewolf syndrome) is an abnormal amount of hair growth over the body. The two distinct types of hypertrichosis are generalized hypertrichosis, which occurs over the entire body, and localized hypertrichosis, w ...

and

hirsutism Hirsutism is excessive body hair on parts of the body where hair is normally absent or minimal. The word is from early 17th century: from Latin ''hirsutus'' meaning "hairy". It usually refers to a male pattern of hair growth in a female that ma ...

. 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, together with increased growth of nose hair. Excessive hair growth within or on the ear is known medically as ''auricular

''. 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

pinnae Pinna may refer to: Biology * Pinna (anatomy), or auricle, the outer part of the ear * ''Pinna'' (bivalve), a genus of molluscs * Pinna (botany), a primary segment of a compound leaf People Surname * Christophe Pinna (born 1968), French marti ...

''" (''hypertrichosis lanuginosa acquisita'').

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 In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological propert ...

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. 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

haplogroup A haplotype is a group of alleles in an organism that are inherited together from a single parent, and a haplogroup (haploid from the , ''haploûs'', "onefold, simple" and ) is a group of similar haplotypes that share a common ancestor with a sing ...

. The hypothesis of Y- linkage would require multiple independent mutations within a single

population Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and pl ...

. 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.

References

{{reflist, 2 Ear Human hair Classical genetics Otorhinolaryngology Otology

Presentation

Genetics

See also

References