Dermatologic History

In this section, I discuss key questions important in taking a dermatologic history and their implications, as well as specific dermatologic lesions and what they tell us. Furthermore, I introduce various tests important in veterinary dermatology, give their indications, explain necessary techniques in detail, and discuss the interpretation of the results.

Dermatologic History

Clinical signs for various skin diseases are very similar and the etiology of a patient's problem may not be apparent based solely on the findings of a clinical examination. A thorough history will typically provide clues in regard to the cause of the skin disorder and allow the veterinarian to prioritize time-consuming and frequently costly laboratory tests needed to confirm the diagnosis. I prefer my clients to fill out a questionnaire in the waiting room which we then review together during the consultation. This decreases the time needed to extract a good history from the owner, helps ensure a complete history independent of stress levels and time constraints, and allows the client to think about her or his pet's skin problem for a little while without unnecessarily delaying the appointment schedule. A sample of a dermatology questionnaire is enclosed in the Appendix. It is important to phrase questions appropriately, because many owners leave out pertinent facts either because they are not aware of their relevance or because they think these facts may not be well received by the veterinarian. Sometimes, it is necessary to ask the same question several times in different ways to obtain meaningful answers. I cannot overemphasize the importance of taking a good and efficient dermatologic history, which requires tremendous knowledge, experience, practice, and effective communication skills. To teach this is beyond the scope of this book. However, I do discuss some crucial questions and their implications in more detail.

Question

What is the breed of the patient?

Relevance

> Some breeds are predisposed to certain skin diseases and it may be worthwhile to keep a list of such breed predispositions within easy reach.

> A list of reported breed predisposition is given in the appendix. But beware, breed predispositions may vary with geographic location!

Question

How old was the patient when clinical signs were first recognized?

Relevance

> Very young animals (puppies and kittens) are more commonly presented with congenital and hereditary defects, ectoparasites such as Sarcoptes scabiei, Otodectes cynotis, or Demodex canis, infections with bacteria (impetigo) or fungi (dermatophytosis) or, in dogs, canine juvenile sterile granulomatous dermatitis and lymphadenitis.

> Young adult dogs are more commonly affected by demodicosis, atopic dermatitis, and flea-bite hypersensitivity, as well as idiopathic seborrhea and follicular dysplasia.

> In middle age, hormonal diseases become a significant consideration, although allergies still occur in a significant number of animals, particularly in cats.

> Neoplastic diseases are more commonly seen in older animals.

Question

How long has the disease been present and how did it progress?

Relevance

> Acute onset of severe pruritus is frequently associated with scabies. Food adverse reaction may also have an explosive onset.

> If pruritus was the first initial sign and lesions occurred later, then atopy or food-adverse reaction are most likely. Pruritus with lesions that occur at approximately the same time may be due to a wide variety of causes.

> Chronic nonlesional pruritus is typically due to atopic dermatitis or food adverse reaction, possibly complicated by secondary infections. Scabies incognito may also cause nonlesional pruritus.

> If cutaneous signs have been present for years without the development of concurrent systemic signs, endocrine disorders are unlikely.

> Nonpruritic alopecia for years without systemic signs points towards alopecia and follicular dysplasias or hereditary alopecia.

> The presence of chronic wounds alone or associated with draining tracts necessitates the search for an infectious organism.

Diagnostic Procedures

Scabies treatment trial, skin scrapings elimination diet, cytology, bacterial culture, fungal culture, biopsy.

Question

Where on the body did the problem start?

Relevance

Table 1-1 and Table 1-2 outline typically affected sites of certain diseases.

Question

Is the animal itchy?

Relevance

> Pruritus is sometimes difficult to identify. Owners often do not consider licking, rubbing, or biting as clinical signs indicative of pruritus (we all have heard the story of the dog that is constantly licking its feet because "it is a very clean dog..."). Several routine questions may be needed to identify pruritus in some patients: Are they licking or chewing their paws? Are they rubbing their faces? Do they scoot on their rear ends? Are they scratching their armpits?

> The presence of pruritus with skin lesions does not help much in discovering the etiology of the pruritus, given that many skin diseases cause pruritus. However, pruritus without lesions typically means either atopic dermatitis or food adverse reaction (possibly with secondary infections) or in rare instances scabies incognito.

> The perceived severity of pruritus may vary with the owner. Some owners deny the presence of pruritus despite the patient's frantic scratching in the consultation room. Others insist on severe pruritus in a patient with no evidence of self-trauma on clinical examination. Good communication skills and judgment are essential to form a realistic opinion for evaluation. If the pet's scratching wakes the owner up at night, the pruritus is severe irrespective of the presence of lesions.

> If itch precedes the occurrence of lesions, atopic dermatitis, food adverse reaction, and scabies incognito must again be considered.

Diagnostic Procedures

Trichogram in alopecic patients that are reportedly nonpruritic.

Question

Is the disease seasonal?

Relevance

> Insect bite hypersensitivities (caused most commonly by fleas, but mosquitoes or other insects can also be involved) frequently cause disease that worsens in summer. Whether clinical signs are absent or milder in the colder season depends on specific environmental conditions.

> Atopic dermatitis may also be seasonal in certain climates. In many temperate climates it may occur more noticeably in spring and summer if caused by tree and grass pollens or worsens in summer and autumn because of weed pollens. Warmer climates such as those found in tropical or subtropical regions usually have an extended pollen season. Hypersensitivities to house dust mites are often nonseasonal, but may be seasonally worse in winter in some areas and patients.

> Seasonal noninflammatory alopecia and hyperpigmentation may be due to cyclic follicular dysplasia.

Diagnostic Procedures

Insect bite trial, intradermal skin testing, serum testing for allergen-specific IgE, biopsy, keeping the animal inside to evaluate for mosquito-bite hypersensitivity.

Question

Are there other clinical signs such as sneezing, coughing, or diarrhea?

Relevance

> Sneezing, coughing, wheezing, and conjunctivitis may be seen concurrently with atopic dermatitis and caused by airborne allergies.

> Diarrhea may be associated with food adverse reaction.

> Polydipsia and polyuria are common with iatrogenic and idiopathic hyperadrenocorticism.

> Systemic mycoses frequently present with concurrent anorexia, lethargy, and with gastrointestinal or respiratory symptoms.

Diagnostic Procedures

Cytology of nasal exudate or conjunctiva, elimination diet, urine cortisol/creatinine ratio, low dose dexamethasone suppression test, and adrenocorticotropic hormone (ACTH)-stimulation test.

Question

What is fed to the animal? Was a special diet used in the past? What was it and how long was it fed exclusively?

Relevance

> Knowing the diet will allow the clinician to determine possible nutritional deficiencies.

> It will also help in formulating an elimination diet if indicated (Part 1 Chap 3).

> If a diet was fed in the past and it was not a true elimination diet (was not fed exclusively or not fed for an appropriate length of time) it may need to be repeated.

Contrary to the common belief, food adverse reactions typically do not occur immediately after a change in feeding habits. Most animals with food adverse reactions have been consuming the offending diet for years before showing clinical signs.

Remember to ask about treats and supplements, which are often forgotten, when food is discussed with the client.

Question

Are there other animals in the household? Do they show cutaneous symptoms?

Relevance

> If other animals in the household are similarly affected, contagious disease such as dermatophytosis or scabies is more likely.

Other animals may serve as a reservoir for ectoparasites without showing clinical signs.

Diagnostic Procedures

If indicated, insect control trial, fungal cultures, or scabies treatment trials should include all animals in the household to identify and/or treat possible carrier animals to allow successful long-term remission for the patient.

Question

Does any person in the household have skin disease?

Relevance

> Two zoonoses of major concern in veterinary dermatology are scabies and dermatophytosis (ringworm). However, even if owners are not affected, these diseases cannot be ruled out.

> Canine scabies affecting humans occurs as an itchy papular rash in contact areas, such as arms and legs, starting days to weeks after onset of pruritus in the pet.

> Dermatophytosis is often characterized by scaling and erythema and may not be particularly pruritic, but occasionally can present as severely inflammatory and pruritic skin disease. Dermatophytosis may sometimes be misdiagnosed as eczema in humans.

> Sporotrichosis and other mycoses have zoonotic potential and may occasionally cause disease in humans.

> Do not forget that the skin disease of the owner may also be completely unrelated to the animal's skin disease.

Diagnostic Procedures

Wood's light, skin scrapings, fungal culture, scabies trial treatment. In severe forms of suspected dermatophytosis, a biopsy and special fungal stains may prove useful for obtaining a quick diagnosis.

Question

Was the disease treated before? If so, which drugs were used and how successful was treatment?

Relevance

Response to previous therapy can be of tremendous help in establishing or ruling out underlying causes for the skin disease.

> Initial response to recent glucocorticoid administration may not be helpful because many skin diseases improve for a short period with this symptomatic, nonspecific treatment.

> Repeated response to low-dose glucocorticoid therapy suggests hypersensitivities (possibly complicated by Malassezia dermatitis caused by Malassezia pachydermatis).

> Repeated response to antibiotics and glucocorticoids in combination is of little help.

> Repeated partial or total response to antibiotics indicates a pyoderma usually secondary to either atopic dermatitis, food adverse reaction, hormonal disease, or another less common disorder that is suppressing the skin's immune system. In addition to antibacterial treatment, the underlying problem needs to be identified and treated to prevent recurrences.

Ask specifically how much the pet improved while receiving medication because many owners tend to judge a treatment as not helpful if it did not cure the disease.

Question

What is currently used to control fleas?

Relevance

> Flea-bite hypersensitivity is the most common hypersensitivity and an extremely common skin disease in most small animal practices. If flea-bite hypersensitivity is suspected, a flea control trial should be commenced.

> Details of the flea control for all animals in the household are important because in a severely allergic animal, clinical signs can be caused by a very small number of flea bites. Inconsistent or ineffective flea control can be discovered only through detailed questioning.

Many owners take questions about their flea control as an insult to their own cleanliness and hygiene. Good communication skills are a great help. I own a flea-allergic dog and routinely mention her as an example, which breaks the ice and increases the client's willingness to listen and follow my instructions.

Question

When was the last medication given?

Relevance

> Recent administration of medication may affect the clinical presentation.

> It may also affect various indicated diagnostic tests that may need to be postponed.

> Long-term glucocorticoid therapy will affect the results of allergy tests - both intradermal skin testing and serum testing for allergen-specific IgE. It will also affect histopathologic findings and the results of many blood tests.

> Antihistamines and short-term systemic and topical glucocorticoids (i.e., < 4 weeks) may influence intradermal skin testing.

> Some antibiotics, such as trimethoprim-sulfonamide combinations, will affect blood concentrations of thyroxine. Others such as cephalosporins may affect the glucose readings of some urine test strips.

> Remember to ask specific questions regarding heartworm prevention, vitamin supplements, or deworming which are also forms of pharmacotherapy.

Question

Does the animal get better with a change of environment (a weekend away or a day at the in-laws for example)?

Relevance

> The animal's improvement in another environment indicates involvement of an environmental allergen (airborne or contact) or irritant.

> Lack of improvement does not rule out these allergies, in that airborne and contact allergens may be the same in different locations (house dust mites are found almost anywhere in the world).