Title: Canine follicular dysplasia

{{more citations|date=February 2024}}
{{short description|Genetic disease in dogs}}
'''Follicular dysplasia''' is a [[genetics|genetic]] disease of [[dog]]s causing [[alopecia]], also called hair loss. It is caused by [[hair follicle]]s that are misfunctioning due to structural abnormality. There are several types, some affecting only certain breeds. Diagnosis is achieved through a [[biopsy]], and treatment is rarely successful. Certain breeds, such as the [[Mexican Hairless Dog]] and [[Chinese Crested Dog]], are bred specifically for alopecia.

==Structural follicular dysplasia==
Structural follicular dysplasia varies by breed but all involve weakened hairs that break easily. Hair loss is originally seen in areas of repeated grooming or trauma, for instance the neck because of contact with a collar. Hair regrowth may occur, but the hair will be even weaker and the pattern will repeat. The dogs are affected between the ages of two and four years, and it is most commonly seen on the back towards the tail. Progression of the hair loss to cover the trunk can occur.

===Commonly affected breeds===
*[[Irish Water Spaniel]]&lt;ref&gt;{{cite book | last=Rhodes | first=Karen Helton | last2=Werner | first2=Alexander H. | title=Blackwell's Five-Minute Veterinary Consult Clinical Companion | publisher=Wiley-Blackwell | publication-place=Ames, Iowa | date=2011-01-25 | isbn=978-0-8138-1596-1 | page=58}}&lt;/ref&gt;
*[[Portuguese Water Dog]]
*[[Curly Coated Retriever]]&lt;ref name=Griffin_2001&gt;{{cite book|last=Griffin|first=Craig E.|author2=Miller, William H. |author3=Scott, Danny W. |year=2001|title=Small Animal Dermatology|edition=6th|publisher=W.B. Saunders Company|isbn=0-7216-7618-9}}&lt;/ref&gt;

==Atrophic follicular dysplasia / pattern baldness==
[[Image:Bald thigh.jpg|thumb|left|A greyhound with ''bald thigh syndrome'', a form of pattern baldness seen in this breed]]
In some breeds hair follicles in certain parts of the body become progressively miniaturized, analogous to what occurs in male pattern baldness in humans. It is most commonly seen in [[Dachshund]]s, [[Miniature Pinscher]]s, and [[Chihuahua (dog)|Chihuahua]]s.&lt;ref&gt;{{cite web | last = Carlotti | first = Didier-Noël | title = Non-Hormonal Alopecia | work = Proceedings of the 30th World Congress of the World Small Animal Veterinary Association | date = 2005 | url = http://www.vin.com/proceedings/Proceedings.plx?CID=WSAVA2005&amp;PID=10979&amp;O=Generic | accessdate = 2007-03-04 }}&lt;/ref&gt; Affected areas become progressively more alopecic. The pattern of hairlessness that results is somewhat breed-dependent and sex dependent. In short-coated toy and miniature dogs, ventral neck, ventral chest, ventral abdomen and inner thighs are affected. In males, the pinnae (ear flaps) are affected. In [[Greyhound]]s, the thighs are affected as well as the ventral chest and abdomen.

==Cyclic follicular dysplasia==
Cyclic follicular dysplasia is also known as '''seasonal alopecia'''. [[Image:Seasonal alopecia.JPG|thumb|Seasonal alopecia]] It causes bilateral hair loss and [[hyperpigmentation]] of the flanks. The disease usually starts in the late fall or early spring, and can regrow in about six months, although the hair may be different in color or texture. Treatment with [[melatonin]] may result in hair regrowth sooner, so it is thought that the amount of daylight influences this condition. The dogs are affected between the ages of two and four years.&lt;ref name=Griffin_2001/&gt;

===Commonly affected breeds===
*[[Airedale Terrier]]
*[[Bulldog]]
*[[Rhodesian Ridgeback]]
*[[Staffordshire Bull Terrier]]
*[[Wirehaired Pointing Griffon]]
*[[Boxer (dog)|Boxer]]
*[[Affenpinscher]]&lt;ref name=Griffin_2001/&gt;

==Follicular lipidosis==
Follicular lipidosis is a type of follicular dysplasia found in the [[Rottweiler]] and other red point dogs.&lt;ref&gt;{{cite book | last=Rhodes | first=Karen Helton | last2=Werner | first2=Alexander H. | title=Blackwell's Five-Minute Veterinary Consult Clinical Companion | publisher=Wiley-Blackwell | publication-place=Ames, Iowa | date=2011-01-25 | isbn=978-0-8138-1596-1 | page=58}}&lt;/ref&gt; It usually occurs before the age of nine months and involves loss of some of the mahogany or red hair of the face and feet. It is caused by [[lipid]] invasion of the hair follicle cells.{{cn|date=February 2024}}

==Color dilution alopecia==
[[Image:Color dilution alopecia 2.jpg|thumb|Color dilution alopecia in a fawn doberman. The close-up of the leg shows the characteristic sparing of the tan color points in this syndrome, only fawn hairs being affected.]]
Color dilution alopecia is caused by a [[dilution gene]] affecting [[eumelanin]]. It is an inherited type of follicular dysplasia. It most commonly affects dogs with [[coat (dog)|blue or fawn coats]], which are dilutions of black and brown, respectively Dilution is caused by irregularities in [[melanin]] transfer and storage. [[Melanosome]]s may clump within [[melanocyte]]s of the skin and hair follicles, causing the hair shafts to easily fracture.&lt;ref&gt;{{cite journal |vauthors=Philipp U, Hamann H, Mecklenburg L, Nishino S, Mignot E, Günzel-Apel A, Schmutz S, Leeb T |title=Polymorphisms within the canine MLPH gene are associated with dilute coat color in dogs |journal=BMC Genet |volume=6|pages=34 |year=2005 |pmid=15960853 |doi=10.1186/1471-2156-6-34 |pmc=1183202 |doi-access=free }}&lt;/ref&gt; Signs of color dilution alopecia include hair loss and recurrent skin infection on the back. It can involve the whole body. The condition starts between the ages of six months and two years, depending on the degree of dilution.&lt;ref&gt;{{cite web | last = Iwasaki | first = Toshiroh | title = Non-Inflammatory Alopecia | work = Proceedings of the 29th World Congress of the World Small Animal Veterinary Association | date = 2004 | url = http://www.vin.com/proceedings/Proceedings.plx?CID=WSAVA2004&amp;PID=8629&amp;O=Generic | accessdate = 2007-03-04 }}&lt;/ref&gt; Early hair loss occurs due to hair breakage, making it similar to structural follicular alopecia. It is important to treat the skin infections, and [[etretinate]] has been used to treat the hair loss. 

In several dog breeds but also in [[mongrel]]s, dogs with the predisposition due to their [[dog coat genetics#D_(dilute)_locus|coat genetics]] with the MLPH gene ([[melanophilin]]) suffer from colour dilution alopecia (CDA). Interestingly in [[Great Dane]]s and [[Weimaraner]]s there are usually no problems due to the dilution gene. The reasons for this are not yet known.&lt;ref&gt;Susanne Schneider: ''[https://www.tieraerztekammer-berlin.de/72-qualzucht/2256-fellfarben-und-genmutation-ein-kurzer-ueberblick.html Fellfarben und Genmutation – ein kurzer Überblick ] {{Webarchive|url=https://web.archive.org/web/20240619003121/https://www.tieraerztekammer-berlin.de/72-qualzucht/2256-fellfarben-und-genmutation-ein-kurzer-ueberblick.html |date=2024-06-19 }}''. Tierärztekammer Berlin.&lt;/ref&gt;

===Commonly affected breeds===
*[[Dobermann]] - has the highest frequency of this condition.&lt;ref name=&quot;Rhodes&quot;&gt;{{cite book | last=Rhodes | first=Karen Helton | last2=Werner | first2=Alexander H. | title=Blackwell's Five-Minute Veterinary Consult Clinical Companion | publisher=Wiley-Blackwell | publication-place=Ames, Iowa | date=2011-01-25 | isbn=978-0-8138-1596-1 | page=58}}&lt;/ref&gt; It occurs in 93 percent of blues and 75 percent of fawns.&lt;ref name=Griffin_2001/&gt;
*[[Dachshund]]
*[[Great Dane]]
*[[Rhodesian Ridgeback]]
*[[Whippet]]
*[[Italian Greyhound]]
*[[Chow Chow]]
*[[Standard Poodle]]
*[[Miniature Pinscher]]
*[[Yorkshire Terrier]]&lt;ref name=&quot;Rhodes&quot;/&gt;
*[[Silky Terrier]]
*[[Chihuahua (dog)|Chihuahua]]
*[[Boston Terrier]]
*[[Newfoundland (dog)|Newfoundland]]
*[[German Shepherd Dog]]
*[[Shetland Sheepdog]]
*[[Schipperke]]
*[[Bernese Mountain Dog]]
*[[Bulldog]]
*[[Mudi]]&lt;ref&gt;{{cite web |title=CDA for a Mudi |url=https://www.northamericanmudialliance.com/mudi-colors |website=North American Mudi Alliance |access-date=5 July 2024}}&lt;/ref&gt;
==Black hair follicular dysplasia==
'''Black hair follicular dysplasia''' only affects black fur. Affected fur will not grow back and dogs are likely to develop skin infections and [[follicular plugging]]. The condition is believed to be caused by an [[autosomal recessive]] trait.&lt;ref name=&quot;englar&quot;/&gt;

Breeds reported to be infected include the [[Dachshund]], [[Jack Russell Terrier]], [[King Charles Cavalier Spaniel]], [[Saluki]], [[Bearded Collie]], [[Border Collie]], [[Beagle]], [[Basset Hound]], [[Pointing breeds|Pointers]], [[Gordon Setter]], [[Doberman Pinscher]], [[Large Münsterländer]]‚ and [[New Zealand Huntaway]].&lt;ref name=&quot;englar&quot;&gt;{{cite book | last=Englar | first=Ryane E. | title=Common Clinical Presentations in Dogs and Cats | publisher=Wiley | date=2019-07-03 | isbn=978-1-119-41458-2 | doi=10.1002/9781119414612 |chapter=Hypotrichosis and Alopecia| page=64}}&lt;/ref&gt;
==Other types of follicular dysplasia==
The [[Siberian Husky]] and [[Alaskan Malamute]] have a type of follicular dysplasia that occurs between the ages of three and four months, possibly later in the Malamute. The [[guard hair]]s of the trunk are progressively lost and the coat turns reddish in color.

In black or red [[Dobermann]]s, [[Miniature Pinscher]]s, and [[Manchester Terrier]]s there is a type of follicular dysplasia that occurs between the ages of one and four years. It begins in the flank and spreads to the back.&lt;ref name=Griffin_2001/&gt;

==References==
{{refbegin}} {{reflist}} {{refend}}

[[Category:Dog diseases|Follicular dysplasia]]