The cause of this alopecic (hair loss) condition in dogs is unclear, but several theories have been proposed. One theory is that the disorder is caused by abnormal adrenal steroidogenesis and is a mild variant of pituitary dependent hyperadrenocorticism. Others have suggested that it may be due to growth hormone deficiency, an adrenal sex hormone imbalance, or excessive production of androgenic steroids by the adrenal glands. Current theories suggest that a local follicular receptor dysregulation may be the underlying disorder. The condition is uncommon in dogs, with the incidence in adult dogs 2-5 years old, especially Chow Chows, Pomeranians, Keeshonds, Samoyeds, Alaskan malamutes, Siberian huskies, and miniature poodles. Gradual loss of primary hairs progresses to complete alopecia of the neck, tail, caudodorsum, perineum, and caudal thighs. The alopecia eventually becomes generalized over the trunk, but the head and front limbs are spared. Hair loss is bilaterally symmetrical, remaining hairs epilate easily, and the alopecic skin may become hyperpigmented, thin, and hypotonic. Mild secondary seborrhea and superficial Pyoderma may occur. No systemic signs of illness are noted.
• Diagnosis- Blood test to rule out other endocrine alopecia (Hormonal hairloss), like Cushings and Hypothyroidism. ACTH stimulation test but false-positive and false-negative results are common, and breed-specific normal values have not been established.
• Treatment- Observation without treatment is reasonable because this disease is purely cosmetic and affected dogs are otherwise healthy. Neutering of intact dogs may induce permanent or temporary hair regrowth. A variety of medical therapies have been used but with inconsistent results. Regardless of the therapy used, hair regrowth may be incomplete or transient. Initial hair regrowth should be seen within 4-8 weeks. If no response is seen after 3 months of treatment, a dosage adjustment or different therapy agent should be considered. The prognosis for hair regrowth is unpredictable. This is a cosmetic disease only that does not affect the dogs quality of life.
Color Dilution Alopecia
Alopecia is a follicular dysplasia of color-dilute hairs that is associated with defective hair pigmentation and formation. An autosomal recessive mode of inheritance is suspected (It is believed to be inherited). It is common in color-dilute dogs such as those bred to be blue, or fawn. The disorder is especially common in Dobermans, but also occurs in other breeds, including Yorkshire terriers, miniature pinschers, Great Danes, Whippets, Italian greyhounds, Salukis, Chow Chows, Dachshunds, Silky terriers, Boston terriers, Newfoundlands, Bernese Mountain dogs, Shetland sheep dogs, Schiperkes, Chihuahuas, Poodles, and Irish setters. Affected dogs appear normal at birth but usually begin losing hair over the dorsum of the trunk between 6 months and 2 years of age. Although the hair coat thinning often progresses to partial or complete hair loss, only the color-diluted hairs are lost. The dog’s normal colored markings are not affected. Secondary skin infection is common.
• Diagnosis- Rule out other hair loss diseases, test with microscopic examination of plucked hairs and sometimes biopsy.
• Treatment- No specific treatment is know that reverses or prevents further hairloss. Treat symptomatically with mild antiseborrheic or antibacterial shampoos and conditioners as needed. Some dogs need antibiotics if infection present. Prognosis is good, Although hair loss is irreversible. This is a cosmetic problem that does not affect the dogs quality of life, however symptomatic skincare may be needed.
Black Hair Follicular Dysplasia
Is a color-linked follicular dysplasia of black hairs that is associated with defective hair pigmentation and formation. It is believed to be inherited, affected puppies appear normal at birth but begin losing hair at around 1 month of age. Only black hairs are affected, with the alopecia progressing until all the black hairs have been lost.
• Diagnosis- Rule out other alopecic diseases, microscopic examination of plucked hairs, and biopsy.
• Treatment- No treatment is know, prognosis is good. Although the alopecia is irreversible, this is a cosmetic problem only that does not affect the dog’s quality of life.
Misc Follicular Dysplasia
Like the other follicular diseases this is believed to be inherited. This type of follicular dysplasias are poorly understood, it is not development or structural , color linked nor seasonal. It is rare in young adult to middle aged dogs, although it is sporadically reported in many breeds; it’s highest incidence is documented in Irish water spaniels, Portuguese water dogs, Pont-Audemer spaniels, black or red Doberman pinchers, and Weimaraners.
• Diagnosis- Again rule out other alopecic causes, perform microscopic examination of plucked hairs and or biopsy.
• Treatment- The animal is treated symptomatically with mild anti-seborrheic or antibacterial shampoos and conditioners as needed. Antibiotics are used if Pyoderma is present. No specific treatment is known, but fatty acid supplementation has been reported in some Irish water spaniels. The prognosis is good, although hair loss is usually irreversible. Again this is a cosmetic problem and does not affect quality of life. Affected dogs should not be bred.
Rabies Vaccine Reaction Hair Loss
With this condition, a focal area of hair loss occurs at the site where a subcutaneous injection of rabies vaccine (or praziquantel, glucocorticoids, or progestational compounds has been administered) A focal, circumscribed to ovoid area of alopecia develops at the injection site 2-4 months post injection. With canine rabies vaccine, the injection site lesion is characterized by a 2-5cm slowly enlarging, flat to slightly indurated patch of alopecia (hairloss) with variable erythema (red skin) that may become mildly scaly, shiny, and centrally hyperpigmented (black skin).
• Diagnosis- Is based on history, clinical findings, ruling out other differentials and occasionally biopsy.
• Treatment- For dogs, no treatment is usually needed. Spontaneous hair regrowth is typical but can take as long as a year to occur. Sometimes topical creams/ointments or oral drugs are prescribed. For dogs whose lesions remain permanently bald surgical excision is curative. Prognosis is usually good, but hair regrowth may not be complete or may have altered pigmentation (black skin).
Flank Alopecia (Hair Loss)
Is a seasonally recurring follicular dysplasia. The exact cause is unknown, but photoperiod control of melatonin and prolactin secretion may be involved. The onset of alopecia in the Northern hemisphere usually occurs between November and March. Most dogs regrow their hair spontaneously 3 to 8 months later. Episodes of hair loss may occur sporadically only once or twice, or regularly each year. With repeated episodes, a progressive increase in the amount and duration of hair loss may be seen. It is uncommon in dogs, with highest incidence in young adult Boxers, bulldogs, Airdales, and Schnauzers.
• Diagnosis- History and clinical findings, rule out other differentials and or Biopsy.
• Treatment- Observation without treatment is reasonable because this disease is purely cosmetic and affected dogs are otherwise healthy. Treatments with melatonin may be effective. The prognosis for hair regrowth is variable. Spontaneous hair regrowth often occurs within 3-8 months, even without treatment. However, regrowth maybe incomplete, and new hairs may be duller in color and drier in texture.
Dermatosis Is an endocrinopathy (hormonal disease) associated with the excessive production of sex hormones or precursor sex hormones by the testes (usually caused by testicular tumors). It is common in intact male dogs , with the highest incidence in middle-aged to older dogs. Sex hormone dermatosis manifests as bilaterally symmetrical alopecia of the neck, rump, perineum, flanks, or trunk that may become generalized but spares the head and limbs. Remaining hairs epilate easily. Alopecic skin may become hyperpigmented. Secondary seborrhea, superficial Pyoderma, and yeast dermatitis may be present. The testicles may be normal, asymmetrical, or cryptorchid on palpatioin. The owner may report that the dog is exhibiting abnormal(eg. Attractiveness to other males, standing in a female posture to urinate) or overly aggressive sexual behavior toward other dogs or humans.
• Diagnosis- Rule out other causes of endocrine (hormonal) alopecia, sex hormone assays: serum levels of one or more sex hormones may be elevated, but false-negative and false-positive results are common. Testicular biopsy (castration) may be normal, atrophic, or neoplastic (sertoli cell tumor, interstitial cell tumor, or seminoma) Response to castration: hair regrowth may occur.
• Treatment- The treatment of choice is castration. Treatment of secondary infections should be treated. The prognosis is excellent for dogs with no tumor metastasis or estrogen-induced myelotoxicity. Hair regrowth should occur within 3 months after castration. Remission followed by relapse may indicate excessive sex hormone production by the adrenal glands (alopecia x) or metastatic testicular neoplasia.
Endocrinopahthy is most often associated with primary thyroid dysfunction caused by Lymphocytic thyroditis or idiopathic thyroid atophy. It is common in dogs, with highest incidence in middle-aged to older dogs. Young adult large and giant-breed dogs are also occasionally affected.
A variety of skin symptoms can be seen. Alopecia (hairloss) on the bridge of the nose occurs in some dogs as an early symptom. The hair coat may be dull, dry and brittle. Bilaterally symmetrical alopecia that spares the extremities may occur, with easily epilated hairs. Alopecic skin may be hyperpigmented, thickened, or cool to the touch. Thicken and dropy facial skin from dermal mucinosis, chronic seborrhea sicca (dry skin) or oleosa (Oily skin with must smell), or ceruminous (ear wax accumulated) Otitis externa may be present. Seborrheic skin and ears may be secondarily infected with yeast or bacteria. In some dogs, the only symptom is recurrent Pyoderma (skin infection) or adult –onset generalized demodicosis. Pruritus is not a primary feature of hypothyroidism and, if present, reflects secondary Pyoderma, malassezia (yeast) infection, or demodicosis. Non cutaneous (skin) symptoms of hypothyroidism are variable and may include aggression, lethargy or mental dullness, exercise intolerance, weight gain or obesity, thermophilia (cold intolerance), bradycardia, vague neuromyopathic or gastrointestinal signs, central nervous system involvement (eg head tilt, nystagmus, hemiparesis, cranial nerve dysfunction, hypermetria) and reproductive problems (eg. Decreased libido, prolonged anestrus, infertility) Puppies with congenital hypothyroidism are disproportionate dwarfs with short limbs and neck relative to their body length.
• Diagnosis- Rule out other causes of hair loss, blood chemistry analysis of total T4 (care must be taken if dog is currently on medications as certain drugs can give false results on the blood test).
• Treatment- Thyroid replacing drugs administered daily for life of pet. Prognosis is good with lifelong replacement of thyroxine therapy. Blood tests should be preformed 4-6 hours post pill to monitor serum level after the first 2-4 months of therapy, and occasionally throughout treatment.
Spontaneously occurring Cushings is excessive production of endogenous steroid (cortisone) hormones, caused by a hyperfunctioning adrenal tumor or pituitary tumor. Iatrogenically induced cushings is secondary to excessive administration of steroids. This type can occur at any age. Spontaneously occurring Cushings tends to occur in middle-aged to older dogs, with an increased incidence noted in Boxers, Boston terriers, Dashshunds, Poodles and Scottish terriers. The hair coat often becomes dry and lusterless, and slowly progressing, bilaterally symmetrical alopecias (hair loss) is common. Cutaneous stria and comedones may be seen on the ventral abdomen. The skin may be mildly seborrhea (fine, dry scales) bruise easily, and exhibit poor wound healing. Chronic secondary or superficial or deep Pyoderma (skin infections) , dermatophytosis (ring worm- fungus infections), or demodicosis is common and may be the clients primary complaint. Calcinosis cutis may develop, especially on the dorsal midline of the neck or ventral abdomen, or the inguinal area. Increase water drinking, and appetite are common, increased urination, muscle wasting or weakness, a pot-bellied appearance, increased susceptibility to infection and excessive panting are often present.
• Diagnosis- ACTH stimulation test is a blood test preformed in a two part test done 90 minutes apart. An exaggerated poststimulation cortisol level is considered a positive Cushings result.
• Treatment-Any concurrent infections should be treated with appropriate therapies. Treatment of choice for iatrogenically induced cases is to progressively taper, then discontinue steroid therapy. For spontaneous Cushings cases oral medications are prescribed daily then ACTH is re-tested after 7-10 days when desired levels are reached medication is continued on a bi-weekly basis for life. With occasional ACTH test to monitor levels as required, based on clinical signs. The prognosis ranges from good to poor, depending on the cause and severity of the disease, with the average survival time for dogs being approximately 2.5 years after diagnosis.