1.8 Non-Endocrine Alopecias – Learning Objectives and General Considerations
Learning Objectives
- Flank Alopecia – Know that some breeds of dogs are at risk to develop a seasonal or cyclic thoracic-lumbar non-inflammatory alopecia.
- Flank Alopecia – Know that boxers, Airedale terriers, and English bulldogs are at higher risk but flank alopecia has been also described in all sizes of schnauzers, miniature Poodles, Doberman pinchers, Bouvier de Flanders, Scottish terriers, French bulldogs, and other breeds.
- Flank Alopecia – Know that most dogs develop seasonal/cyclic flank alopecia between 3 to 6 years of age (mean 3.8 years).
- Flank Alopecia – Be aware! Typically, the alopecia is bilateral and localized to the lateral to dorsolateral thoracic-lumbar region and often has an annular to polycyclic configuration. The associated skin is usually markedly hyperpigmented.
- Flank Alopecia – Be aware! Most dogs in the northern hemisphere lose hair in the late fall and regrow it spontaneously in the spring or summer; 20% of dogs will only have one episode of hair loss. The hair coat typically re-grows in 1 to 14 months but the condition may become permanent.
- Flank Alopecia – Know that definitive diagnosis of seasonal/cyclic flank alopecia should be based on a characteristic history, typical clinical signs, and laboratory test results that rule out other conditions especially hypothyroidism, alopecia X, and sex hormone related alopecias.
- Flank Alopecia – Be aware! There is currently no effective therapy for seasonal/cyclic flank alopecia and because affected dogs are healthy otherwise, benign neglect is a reasonable option. However, melatonin implants, melatonin injection or oral melatonin have been used to manage this condition with variable results and should be considered as options if owners request treatment.
- Alopecia X – Know that alopecia X is seen especially in young dogs at the age of 1 to 3 years but clinical signs can develop at any time between the ages of 1 to 10 years. The disease has been recognized in intact or neutered animals. There is breed predilection for chow chows, Pomeranians, keeshondens, Samoyeds and miniature poodles.
- Alopecia X – Be aware! The cause of alopecia X is unknown. Genetic factors may play a role since certain breeds are more often affected and it may occur in related dogs. The most recent theory suggests that the follicular arrest is related to increase activity of estrogen receptors at the level of hair follicles.
- Alopecia X – Know! The initial clinical sign of alopecia X is a dull and dry hair coat along the trunk that progresses to loss of guard hairs resulting in a puppy-like appearance of the hair coat. Eventually, alopecia and severe hyperpigmentation develop on the neck, perineum, caudal dorsal back, and caudal thighs. Head and legs are typically spared as for other endocrinopathies.
- Alopecia X – Know! The definitive diagnosis of alopecia X should be based on a characteristic history and clinical signs, and laboratory test results that rule out other disorders associated with non-inflammatory alopecia such as, hypothyroidism, sex hormone imbalance in intact dogs, hyperadrenocorticism, follicular dysplasia, and flank alopecia.
- Alopecia X – Be aware! If you have ruled out other dermatoses associated with non-inflammatory alopecia, you do not need to treat alopecia X cases.
- Alopecia X – Remember! Neutering intact animals is always a good diagnostic and treatment trial for dogs suspected of having alopecia X.
- Alopecia X – Know! If an intact dog with alopecia X has been neutered and/or the owner wants to try medical therapy the options are: melatonin, deslorelin, and trilostane or mitotane. However, remember to discuss with the client that this is a cosmetic disease and trilostane and mitotane can have potentially serious side effects.
- Alopecia X – Remember to also discuss with the owner that any improvement because of an intervention may not be long lasting.
- Follicular dysplasia – Know that follicular dysplasia is in general a breed specific condition associated with alopecia and/or various coat changes such as dry, frizzy and poor hair coats, changes in coat color, loss of primary hairs, and curly or twisted hair shafts.
- Follicular dysplasia – Remember! Diseases typically classified under follicular dysplasias include color dilution alopecia, black hair follicular dysplasia, and non-color-linked follicular dysplasias.
- Follicular dysplasia – Be aware! Color dilution alopecia is an inherited disease that develops in some (not all) dogs with blue (dilution of black) or fawn (dilution of brown) color.
- Follicular dysplasia – Know! The incidence of color dilution alopecia varies according to the breed. It occurs in about 93% and 73% of blue and fawn Doberman pinchers, respectively, while most Weimaraners will not develop the disease.
- Follicular dysplasia – Know that clinical signs typically start between 3 months and 3 years of age and dogs with more diluted coat colors (e.g. gray) will develop alopecia earlier than dogs with less diluted coat colors (e.g. steel blue). Most light-colored diluted coats are completely alopecic by 2 to 3 years of age.
- Follicular dysplasia – Be aware! Microscopic examination of hair shafts (trichoscopy) and histopathology will show large clumps of melanin that will distort their normal structures. These features in conjunction with a characteristic history of alopecia limited to color dilute hairs that started between 3 months and 3 years of age are diagnostic of color dilution alopecia.
- Follicular dysplasia – Know that treatment is palliative and should focus on treating and preventing secondary skin infections and avoiding sun exposure of the alopecic areas.
- Follicular dysplasia – Know that black hair follicular dysplasia is associated with hair loss limited to the black coat of bicolor or tricolor dogs and that it typically starts earlier than color dilution alopecia, at about 1 month of age, and it has been reported in various breeds.
- Follicular dysplasia – Know! The diagnosis of black hair follicle dysplasia is based on a characteristic history, typical clinical signs, and findings of the trichoscopy and histopathology, which are characterized by melanin clumping in the hair shaft, follicular wall, follicular canal, and perifollicular region. The melanin clumps present in the skin and hairs are not as pronounced as they are in color dilution alopecia.
- Follicular dysplasia – Know that there is no treatment for black hair follicular dysplasia. Owners should be advised to not breed the dog as genetic plays a role in disease development.
- Follicular dysplasia – Be aware of the breeds reported to develop non-color-linked follicular dysplasias, which include Siberian huskies, Alaskan malamutes, Doberman pinchers, miniature pinchers, Manchester terriers, Irish water spaniels, Portuguese water dogs, curly-coated retrievers, Weimaraners, and anecdotally, other breeds.
- Follicular dysplasia – Be aware that age of onset varies according to the breed but most cases develop alopecia between 1 and 4 years of age. The clinical signs also vary according to the breeds and the breed differences.
- Follicular dysplasia – Know that histopathology shows follicular dysplasia with melanin clumping but less prominent than in color dilution alopecia.
- Follicular dysplasia – Remember! There is no specific treatment for follicular dysplasias.
- Pattern baldness – Know that pattern baldness is a relatively common canine disorder that affects dogs of either sex independent of their reproductive status.
- Pattern baldness – Be aware that in contrast to most follicular dysplasias discussed previously, the hair loss in pattern baldness typically starts before 1 year of age.
- Pattern baldness – Remember that pattern baldness occurs predominantly in short-coated breeds.
- Pattern baldness – Be aware that distribution of the hair loss in pattern baldness is typically related to the breed and the various clinical presentations can be grouped as follows: (i) pinnal alopecia of dachshunds, (ii) pattern baldness of American water spaniels where the alopecia develops on the ventral and lateral neck, trunk, rump, and caudal thighs (iii) pattern baldness of greyhounds where the alopecia develops on the caudal thighs, and (iv) predominantly ventral alopecia of short-coated breeds where the alopecia occurs on the pre- and post-auricular areas, ventral neck, entire ventrum, and caudomedial thighs. This condition is recognized more frequently in dachshunds but has also been described in Boston terriers, whippets, Chihuahuas, Manchester terriers, greyhounds, and Italian greyhounds.
- Pattern baldness – Be aware! The development of non-inflammatory alopecia before 1 year of age in predisposed breeds suggests pattern baldness alopecia.
- Pattern baldness -Be aware! The histopathology findings of pattern baldness differ from the ones present in coat-color-linked and non-coat-color-linked follicular dysplasias and show miniaturization of hair follicles characterized by shorter and thinner follicles with smaller bulbs.
- Pattern baldness – Remember! Melatonin at the dose of 3 to 6 mg/dog every 8 to 12 hours may result in significant hair re-growth within 3 to 4 months.
- Post-clipping alopecia – Know that post-clipping alopecia may occur after the hair is clipped for any reason.
- Post-clipping alopecia – Be aware! There is no age or sex predilection for post-clipping alopecia but plush-coated breeds may be predisposed.
- Post-clipping alopecia – Be aware! Hairs may not re-grow after 1 (most cases) to 2 years after clipping.
- Post-clipping alopecia – Make sure to rule out hypothyroidism or sex hormone-related alopecia in middle age to older dogs that fail to re-grow hair after clipping.
- Post-clipping alopecia – Remember! The histopathological findings of post-clipping alopecia are not specific and show most hair follicles in telogen phase.
- Post-clipping alopecia – Be aware! There is no need to treat this condition but melatonin can be tried if owners require an intervention; however, no studies have been done to demonstrate its efficacy for post-clipping alopecia.
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General Considerations
- The breed predilection associated with many of the non-endocrine and non-inflammatory alopecias described here indicates that genetic plays a role in disease development.
- In contrast to endocrine alopecic diseases that typically spare the head and extremities (with the exception of the caudal thighs), the pattern of alopecia in the diseases described here is quite variable and depends on the breed and disease.
- Similar to endocrine alopecic diseases, the conditions presented in this section are non-inflammatory and non-pruritic. However, if secondary bacterial infection and/or bacterial and yeast overgrowth develop at any time during the disease, the dog may become pruritic.
- Alopecia X (hair follicle arrest) and seasonal/cyclic flank alopecia are included in this section because despite the fact that there is some evidence that hormone may play a role in disease development, the pathogenesis of these two alopecic disorders is still not complete understood and hormone may not be the sole or main culprit.
