Follicular dysplasia is a genetic disease of

dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...

s causing

alopecia Hair loss, also known as alopecia or baldness, refers to a loss of hair from part of the head or body. Typically at least the head is involved. The severity of hair loss can vary from a small area to the entire body. Inflammation or scarri ...

, also called hair loss. It is caused by

hair follicle The hair follicle is an organ found in mammalian skin. It resides in the dermal layer of the skin and is made up of 20 different cell types, each with distinct functions. The hair follicle regulates hair growth via a complex interaction between h ...

s that are misfunctioning due to structural abnormality. There are several types, some affecting only certain breeds. Diagnosis is achieved through a

biopsy A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a diseas ...

, and treatment is rarely successful. Certain breeds, such as the

Mexican Hairless Dog The Xoloitzcuintle (or Xoloitzquintle, Xoloitzcuintli, or Xolo) is one of several breeds of hairless dog. It is found in standard, intermediate, and miniature sizes. The Xolo also comes in a coated variety, totally covered in fur. Coated and hair ...

and

Chinese Crested Dog The Chinese Crested Dog is a hairless breed of dog. Like most hairless dog breeds, the Chinese Crested Dog comes in three varieties, with hair, without hair and a combination of the two, which can be born in the same litter: the Powderpuff, the H ...

, 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 to 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 The Irish Water Spaniel ( Irish: ''An Spáinnéar Uisce'') is a breed of dog that is the tallest of the spaniels. Description Appearance The Irish Water Spaniel is a sturdy, cobby dog native to Ireland. The coat, consisting of dense cur ...

Portuguese Water Dog The Portuguese Water Dog originated from the Algarve region of Portugal. From there the breed expanded to all around Portugal's coast, where they were taught to herd fish into fishermen's nets, retrieve lost tackle or broken nets, and act as ...

Curly Coated Retriever The Curly-coated Retriever (not always hyphenated, and often called the Curly for short) is a breed of dog originally bred in England for upland bird and waterfowl hunting. It is the tallest of the retrievers and is easily distinguishable by t ...

Atrophic follicular dysplasia / Pattern baldness

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 Dachshunds,

Miniature Pinscher The Miniature Pinscher, also known as the Zwergpinscher and Mini Pin, is a small breed of dog of the pinscher type originating in Germany. The breed's earliest ancestors may have included the German Pinscher mixed with Italian greyhounds and dachs ...

s, and Chihuahuas. 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 The English Greyhound, or simply the Greyhound, is a breed of dog, a sighthound which has been bred for coursing, greyhound racing and hunting. Since the rise in large-scale adoption of retired racing Greyhounds, the breed has seen a resurge ...

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. It causes bilateral hair loss and

hyperpigmentation Hyperpigmentation is the darkening of an area of skin or nails caused by increased melanin. Causes Hyperpigmentation can be caused by sun damage, inflammation, or other skin injuries, including those related to acne vulgaris.James, William; Ber ...

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 to four years.

Commonly affected breeds

* Silver Labrador *

Airedale Terrier The Airedale Terrier (often shortened to "Airedale"), also called Bingley Terrier and Waterside Terrier, is a dog breed of the terrier type that originated in the valley (''dale'') of the River Aire, in the West Riding of Yorkshire, England. It ...

Bulldog The Bulldog is a British breed of dog of mastiff type. It may also be known as the English Bulldog or British Bulldog. It is of medium size, a muscular, hefty dog with a wrinkled face and a distinctive pushed-in nose.Staffordshire Bull Terrier The Staffordshire Bull Terrier, also called the Staffy or Stafford, is a dog breed, purebred dog of small to medium size in the Terrier Group, terrier group that originated in the northern parts of Birmingham and in the Black Country of Staff ...

Wirehaired Pointing Griffon The Wirehaired Pointing Griffon (also called the Korthals Griffon and the Griffon d'arrêt à poil dur Korthals in France and Quebec) is a breed of dog used in hunting as a gundog. It is sometimes considered to be Dutch in ancestry, due to t ...

Boxer Boxer most commonly refers to: * Boxer (boxing), a competitor in the sport of boxing *Boxer (dog), a breed of dog Boxer or boxers may also refer to: Animal kingdom * Boxer crab * Boxer shrimp, a small group of decapod crustaceans * Boxer snipe ee ...

Affenpinscher The Affenpinscher, also known as the Monkey Terrier, is a terrier-like toy Pinscher breed of dog. History The breed is German in origin and dates back to the seventeenth century. The name "affenpinscher" is derived from the German ''Affe'' (a ...

Follicular lipidosis

Follicular lipidosis is a type of follicular dysplasia found in the

Rottweiler The Rottweiler (, ) is a breed of domestic dog, regarded as medium-to-large or large. The dogs were known in German as , meaning Rottweil butchers' dogs, because their main use was to herd livestock and pull carts laden with butchered mea ...

. 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 Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...

invasion of the hair follicle cells.

Color dilution alopecia

Color dilution alopecia is caused by a dilution gene affecting

eumelanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amin ...

. It is an inherited type of follicular dysplasia. It most commonly affects dogs with blue or fawn coats, which are dilutions of black and brown, respectively Dilution is caused by irregularities in

melanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino ...

transfer and storage.

Melanosome A melanosome is an organelle found in animal cells and is the site for synthesis, storage and transport of melanin, the most common light-absorbing pigment found in the animal kingdom. Melanosomes are responsible for color and photoprotection i ...

s may clump within

melanocyte Melanocytes are melanin-producing neural crest-derived cells located in the bottom layer (the stratum basale) of the skin's epidermis, the middle layer of the eye (the uvea), the inner ear, vaginal epithelium, meninges, bones, and heart. ...

s of the skin and hair follicles, causing the hair shafts to easily fracture. 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. 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 A mongrel, mutt or mixed-breed dog is a dog that does not belong to one officially recognized Dog breed, breed and including those that are the result of intentional Dog breeding, breeding. Although the term ''mixed-breed dog'' is sometime ...

s, dogs with the predisposition due to their coat genetics with the MLPH gene (

melanophilin Melanophilin is a carrier protein which in humans is encoded by the ''MLPH'' gene. Several alternatively spliced transcript variants of this gene have been described, but the full-length nature of some of these variants has not been determined. ...

) suffer from colour dilution alopecia (CDA). Interestingly in

Great Dane The Great Dane is a large sized dog breed originating from Germany. The Great Dane descends from hunting dogs from the Middle Ages used to hunt wild boar and deer, and as guardians of German nobility. It is one of the largest breeds in the world ...

s and

Weimaraner The Weimaraner ( ) is a large dog that was originally bred as a hunting dog in the early 19th century. Early Weimaraners were used by royalty for hunting large game such as boar, bear and deer. As the popularity of large game hunting began to ...

s there are usually no problems due to the dilution gene. The reasons for this are not yet known.

Commonly affected breeds

Rhodesian Ridgeback The Rhodesian Ridgeback is a large dog breed bred in the Southern Africa region. Its forebears can be traced to the semi-domesticated ridged hunting and guardian dogs of the Khoikhoi. These were interbred with European dogs by the early colonist ...

Whippet The Whippet is a dog breed of medium size. It is a sighthound breed that originated in England, descended from the Greyhound. Whippets today still strongly resemble a smaller Greyhound. Part of the hound group, Whippets have relatively few ...

Italian Greyhound The Italian Greyhound ( it, Piccolo levriero Italiano, italic=no) is an Italian breed of small sighthound. It may also be called the Italian Sighthound. History Small dogs of sighthound type have long been popular with nobility and royalty. ...

Chow Chow The Chow Chow is a spitz-type of dog breed originally from northern China. The Chow Chow is a sturdily built dog, square in profile, with a broad skull and small, triangular, erect ears with rounded tips. The breed is known for a very dense ...

* Standard Poodle *

Yorkshire Terrier The Yorkshire Terrier (often shortened as Yorkie) is one of the smallest dog breeds of the terrier type and indeed of any dog breed. The breed developed during the 19th century in Yorkshire, England.Silky Terrier The Australian Silky Terrier or simply Silky Terrier (depending on the breed registry) is a small breed of dog of the terrier dog type. The breed was developed in Australia, although the ancestral types and breeds were from Great Britain. It is ...

* Chihuahua *

Boston Terrier The Boston Terrier is a breed of dog originating in the United States of America. This "American Gentleman" was accepted in 1893 by the American Kennel Club as a non-sporting breed. Color and markings are important when distinguishing this breed f ...

Newfoundland Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...

* German Shepherd Dog *

Shetland Sheepdog The Shetland Sheepdog, often known as the Sheltie, is a breed of herding dog that originated in the Shetland Islands of Scotland. The original name was ''Shetland Collie,'' but this caused controversy amongst Rough Collie breeders of the time, s ...

Schipperke A Schipperke (; ) is a small breed of dog that originated since the 1600s in Belgium. There has been a long informal debate over whether this type of dog is a spitz or miniature sheepdog. In their home country of Belgium they are considered a sm ...

Bernese Mountain Dog The Bernese Mountain Dog (german: Berner Sennenhund) is a large dog breed, one of the four breeds of Sennenhund- type dogs from Bern, Switzerland and the Swiss Alps. These dogs have roots in the Roman mastiffs. The name ''Sennenhund'' is derived ...

Alaskan Malamute The Alaskan Malamute () is a large breed of dog that was originally bred for its strength and endurance to haul heavy freight as a sled dog and hound. It is similar to other arctic breeds such as the husky, the spitz, the Greenland Dog, Canad ...

have a type of follicular dysplasia that occurs between the ages of three and four months, possibly later in the Malamute. The

guard hair Guard hair or overhair is the outer layer of hair of most mammals, which overlay the fur. Guard hairs are long and coarse and protect the rest of the pelage (fur) from abrasion and frequently from moisture. They are visible on the surface of the fu ...

s of the trunk are progressively lost and the coat turns reddish in color. In black or red

Dobermann The Dobermann (; ), or Doberman Pinscher in the United States and Canada, is a medium-large breed of domestic dog that was originally developed around 1890 by Louis Dobermann, a tax collector from Germany.Miniature Pinscher The Miniature Pinscher, also known as the Zwergpinscher and Mini Pin, is a small breed of dog of the pinscher type originating in Germany. The breed's earliest ancestors may have included the German Pinscher mixed with Italian greyhounds and dachs ...

s, and

Manchester Terrier The Manchester Terrier is a breed of dog of the smooth-haired terrier type. It was first bred in the 19th century to control vermin, notably rats, at which it excelled. So efficient at the task was it that it often appeared in rat-baiting pits ...

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. Black hair follicular dysplasia occurs in

piebald A piebald or pied animal is one that has a pattern of unpigmented spots (white) on a pigmented background of hair, feathers or scales. Thus a piebald black and white dog is a black dog with white spots. The animal's skin under the white backgro ...

dogs and causes hair loss in black-haired areas soon after birth. It is most commonly seen in

Papillon (dog) The Papillon (, French for 'butterfly eared), also called the Continental Toy Spaniel, is a breed of dog, of the spaniel type. One of the oldest of the toy spaniels, it derives its name from its characteristic butterfly-like look of the long ...

, Gordon setter, Saluki and

Bearded Collie The Bearded Collie, or Beardie, is a herding breed of dog once used primarily by Scottish shepherds, but now mostly a popular family companion. Bearded Collies have an average weight of . Males are around tall at the withers while females are ...

, and is known to occur in Large Münsterländer dogs. It is considered to be similar to color dilution alopecia and is inherited as an

autosomal recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...

trait.

References

{{refend Follicular dysplasia