The Dog with Alopecia
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MAY 22, 2006
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Table of Contents
- The Pruritic Dog
- The Dog with Papules, Pustules, and Crusts
- The Dog with Alopecia
In this section, I offer an approach to various common presentations in veterinary dermatology. I begin each topic in this section with general comments followed by tables containing the most common differential diagnoses, their clinical features, diagnostic procedures of choice, treatment, and prognosis. I have attempted to list diseases in order of prevalence. Diseases marked with an ( # ) and a colored screen, are potentially difficult to diagnose or their management often requires considerable experience to achieve the best possible outcome. You may consider offering your client a referral to a veterinary dermatologist if you do not feel comfortable diagnosing or treating this disease.
This is not a textbook of veterinary dermatology so these tables do not contain all possible details but rather a concise overview concentrating on the most important features. Similarly, the flow charts at the end of each topic are concise and simplified to maximize the benefit for the busy small animal practitioner. They will be useful in most instances, but remember that some of your clients may not have read the textbooks. Even though this information is aimed at helping you as competent veterinarians to reach a diagnosis and formulate a treatment plan, your critical acumen, examination, and communication skills remain the most crucial instruments for success in your daily practice.
3. The Dog with Alopecia
Many diseases are associated with alopecia in conjunction with pruritus and other lesions. Here we discuss dogs with clinically noninflammatory alopecias.
Key Questions
> What is the breed of this patient?
> How old was this patient when clinical signs were first recognized?
> How long has the disease been present and how did it progress?
> On which part of the body did the problem start?
> Is the animal itchy?
> Is the disease seasonal?
> Are there any other animals in the household?
> Does anybody in the household have skin disease?
> Was the disease treated before? If so, which drugs were used and how successful was treatment?
If the alopecic dog is pruritic but lacks other lesions, the approach is different from that used in a bald dog without pruritus. Many alopecias are characterized by dry skin and mild scaling, which may or may not be pruritic. The use of moisturizers will help the dryness and may address concurrent pruritus. If pruritus persists, then the approach is the same as for the dog with pruritus without lesions. Differential diagnoses for noninflammatory and nonpruritic alopecias are outlined later in this section.
Table 2-5. Differential Diagnoses, Commonly Affected Sites, Recommended Diagnostic Tests, Treatment Options, and Prognosis in Dogs with Noninflammatory, Nonpruritic Alopecia | ||||
Disease | Commonly Affected Sites | Diagnostic Tests | Treatment | Prognosis |
Hyperadrenocorticism (#) (spontaneous or idiopathic) The spontaneous form is an excessive production of glucocorticoids due either to a microadenoma or macroadenoma of the pituitary gland - pituitary-dependent hyperadrenocorticism [=PDH], in 85% - or due to adrenocortical neoplasms in 15%) | Polyuria, polydipsia, polyphagia, dull haircoat, slow hair growth, coat color change, partial-to-complete symmetric alopecia of the rump, thin skin, recurrent skin and bladder infections, exercise intolerance, panting, muscle atrophy, anestrus, calcinosis cutis (Fig. 2-28), behavioral changes, and neurologic signs (the latter with a pituitary macroadenoma) | Serum biochemistry (Serum alkaline phosphatase [SAP] ↑ cholesterol ↑, alanine aminotransferase [ALT] ↑, glucose ↑, urea ↓), hemogram (leukocytosis, neutrophilia, lymphopenia, and eosinopenia), urinalysis (specific gravity ↓ cortisol:creatinine ratio ↑), radiographs (hepatomegaly, osteoporosis, mineralization of adrenal glands), low dose dexamethasone suppression test, adrenocorticotropic hormone (ACTH) in PDH ↑, ultrasonography (adrenal gland size ↑), ACTH stimulation test | Iatrogenic form: Cautiously taper and then discontinue glucocorticoid administration. Idiopathic form: o,p´- DDD (mitotane), ketoconazole for pituitary-dependent hyperadrenocorticism , surgical removal of affected gland for adrenocortical neoplasia | Approximately 60% of dogs with adrenal tumors were reported to survive adrenalectomy and the postoperative period. The average life expectancy was 36 months. Adrenal adenomas have a better prognosis than adenocarcinomas. The life span of dogs with PDH treated medically averaged 30 months with some dogs living longer than 10 years and others only days. |
Hypothyroidism (lymphocytic thyroiditis [presumably autoimmune] or idiopathic thyroid necrosis which may be end-stage lymphocytic thyroiditis) | Lethargy, obesity, depression, dull brittle coat, recurrent skin infections, thick, puffy skin (myxedema), hypotrichosis, alopecia (frictional areas, flanks, trunk, face), hypertrichosis (Boxers), seborrhea, neuromuscular symptoms, infertility | Serum biochemistry (SAP↑, cholesterol [↑], ALT ↑), hemogram (anemia), thyroid tests (free thyroxine [T4], total T4, free T4 by equilibrium dialysis, thyroid stimulating hormone (TSH) assays, TSH stimulation test, thyrotropin-releasing hormone (TRH) stimulation test) | Hormone replacement therapy with levothyroxine. | Good, although not all patients stay in complete and constant remission despite adequate supplementation |
Follicular dysplasia (unknown etiology) | Noninflammatory alopecia sparing the head and limbs (Fig. 2-29) | Biopsy, ruling out endocrine disorders in equivocal cases. | Retinoids, melatonin | Excellent for wellbeing, guarded for hair regrowth |
Cyclic follicular dysplasia (possibly related to duration of daily light exposure) | Seasonal local hyperpigmentation and alopecia of the trunk (often the flanks) with initially spontaneous regrowth after 3 to 4 months (Fig. 2-30) | Biopsy | Melatonin | Excellent for general well-being, fair for prevention of hair loss with treatment |
Pattern baldness (unknown etiology, probably genetically determined). Dachshunds and Greyhounds are predisposed | Alopecia of pinnae, postauricular region, ventral neck, ventrum, caudomedial thighs, tail (Fig. 2-31) | Biopsy, lack of endocrine abnormalities. | Benign neglect possibly in conjunction with moisturizers | Excellent for well-being, poor for hair regrowth |
Color dilution alopecia (genetically determined degenerative process resulting in lighter hair color with pigmentary clumping and damage to the hair shaft and bulb) | Alopecia of dilute blue or fawn colored areas, often with scaliness and recurrent folliculitis (Fig. 2-32) | Cytology, trichogram, skin scrapings, biopsy | Retinoids, essential fatty acid supplementation | Good for well-being, poor for hair regrowth |
Growth hormone-responsive dermatosis, estrogen responsive dermatosis, castration-responsive dermatosis, adrenal sex hormone imbalance, testosterone-responsive dermatosis, hypogonadism (unclear etiology in most of these syndromes that may be grouped together as "alopecia x") | Puppy-like hair coat, coat color changes, hypotrichosis and alopecia of the perineal and genital region, flank, trunk, neck (Fig. 2-33 and Fig. 2-34) | Biopsy in conjunction with ruling out other endocrine disorders, such as hyperadrenocorticism and hypothyroidism, that may have similar histopathologic changes | Benign neglect in conjunction with moisturizers and possibly antimicrobial treatment, neutering in intact dogs, testosterone in castrated males, estrogen in spayed females, growth hormone (diabetogenic), o,p'- DDD (risk of hypoadrenocorticism) | Good for well-being, treatment usually only leads to temporary remission |
Sertoli's cell tumor (most common in cryptorchid testicles, increased levels of estrogen) | Bilaterally symmetric alopecia of wear areas such as collar region, rump, perineum and genital area, gynecomastia, pendulous prepuce, attraction of male dogs, linear preputial dermatosis, prostatomegaly, prostatitis, estrogen-induced bone marrow suppression | Blood estrogen ↑, skin biopsy, histopathologic evaluation of removed testes | Castration | Excellent with no metastases, guarded with metastases or aplastic anemia |
Hyperestrogenism (Cystic ovaries or functional ovarian tumors) | Bilaterally symmetric alopecia of perineum, inguinal area and flanks, gynecomastia, and comedones, estrus cycle abnormalities | Biopsy, blood estrogen ↑, ultrasonography, laparoscopy | Ovariohysterectomy | Excellent |
Anagen defluxion (severe systemic diseases or antimitotic drugs interfere with hair growth, resulting in abnormal hair shafts, hair breaks off suddenly) | Alopecia of sudden onset | History, trichogram | Addressing the underlying cause | Excellent if causative factor is addressed successfully |
Telogen effluvium (severe stress [e.g. shock, fever, surgery] causes abrupt cessation of hair growth and switching to catagen and then telogen in many follicles, which are all shed simultaneously 1 to 3 months after the insult) | Focal to generalized alopecia of sudden onset | History, trichogram | Not needed, if stress was a one-time event | Excellent |
Post-clipping Alopecia (arctic or plush coated breeds fail to regrow hair in clipped areas; cause is unknown) | Clipped areas | Diagnosis based on signalment, history, and presence of noninflammatory alopecia in clipped areas only. | None. Hair will grow back in 6 - 24 months | Excellent |
Figure 2-28. Papules and crusts in an 8-year-old, male castrated Bull Terrier with calcinosis cutis due to pituitary-dependent hyperadrenocorticism.
Figure 2-29. Alopecia due to follicular dysplasia in a 2-year-old, female Curly-coated Retriever.
Figure 2-30. Alopecia and hyperpigmentation in the flank area of a 6-year-old, male castrated Boxer with cyclic follicular dysplasia.
Figure 2-31. Pattern alopecia (Courtesy of Dr. Peter Ihrke).
Figure 2-32. Color dilution alopecia in a 3-year-old, female Yorkshire Terrier (Courtesy of Dr. Thierry Olivry).
Figure 2-33. Growth hormone- responsive dermatosis in a 9-year-old, spayed Keeshond.
Figure 2-34. Castration-responsive dermatosis in a 5-year-old male Keeshond (Courtesy of Dr. Sonya Bettenay).
Figure 2-35. The dog with noninflammatory nonpruritic alopecia.
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How to reference this publication (Harvard system)?
(2006) “The Dog with Alopecia”, Dermatology for the Small Animal Practitioner. Available at: https://www.ivis.org/library/dermatology-for-small-animal-practitioner/dog-alopecia (Accessed: 11 September 2024).
Affiliation of the authors at the time of publication
Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.
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ISBN-10
1893441091
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