Pet owner educational atlas. Diagnosis in dermatology. Second edition

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STRUCTURE AND FUNCTION

5 The skin barrier Many factors can affect the integrity of the skin and the skin barrier. These can be grouped as follows: genetic factors, environmental factors, and diseases or inflammatory processes of the skin.

Environmental factors

External agents ■

Excessive humidity or dryness, exposure to heat sources or excessive sun exposure.

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Trauma

Bacteria and yeasts, which can proliferate and cause infections that further damage the skin.

Environmental allergens such as pollens and house and storage mites.

Dermatitis = inflammation

Alterations of the skin barrier

Sensitisation to allergens

Pruritus

Overactive immune system

Inflammation of the skin

Genetic factors Diseases with a genetic component such as atopic dermatitis (or environmental allergy), sebaceous adenitis, follicular dysplasias, ichthyosis, etc.

Scratching, licking, or nibbling causes and exacerbates inflammation, further altering the skin barrier.

Associated with any skin disease.

Skin genes

Atopy genes

Treatment ■ ■

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Shampoo therapy with restructuring and hydrating shampoos.

Lotions, foams, or pipettes with ingredients that help restore the structure of the skin and the skin barrier.

Diet plays a very important role.

The veterinary surgeon will provide advice on the best treatment for each patient based on their disease or the specific characteristics of their skin.

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All damaged, inflamed, or sensitive skin must be treated to maintain its structure and the composition of its secretions, and to restructure the skin barrier.

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PET OWNER EDUCATIONAL ATLAS. DIAGNOSIS IN DERMATOLOGY

PRURITUS

20 Flea allergy dermatitis (FAD) Diagnostic protocol for allergic triad The presence of fleas on an animal indicates an infestation. Not all animals with fleas are allergic to their bite.

The presence of fleas (or evidence thereof) on an animal is always indicative of an environmental infestation.

FAD is an allergic disease characterised by itching, generally affecting the rump, tail, and abdominal area.

Other potential lesions in addition to itching include alopecia, papules, erythema, and acute moist pyoderma.

The importance of environmental control

In FAD, clinical signs are not observed if contact with fleas is avoided. Therefore, allergic animals require effective flea control throughout the year.

The disease will not resolve until the environmental infestation is controlled. Animals should receive an effective treatment against fleas throughout the year.

Diagnostic protocol

Itching + fleas

Itching + flea faeces

Itching without fleas or flea faeces

Easy diagnosis, well accepted by the owner

The potential diagnosis is harder to accept

FAD cannot be ruled out

Effective treatment against fleas in the animal and its environment

The owner tends not to accept the potential diagnosis

Requires serological test for flea allergy and effective antiparasitic treatment

Treatment Isoxazolines are the drugs with the fastest and longest lasting effect. They are effective for both treatment and prevention.

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PRURITUS

22 Atopic dermatitis Diagnostic protocol for allergic triad Atopic dermatitis is an inflammatory disease caused by an exaggerated reaction of the animal’s immune system against environmental allergens (mites, pollens, mould, animal epithelia). Avoiding contact with these substances is not possible. High environmental loads of allergens exacerbate the process. The diagnosis of atopic dermatitis is based on the patient’s clinical history and clinical picture, after ruling out flea bite and food allergies.

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Pruritus or itching is a consequence of inflammation: the animal scratches and develops lesions, further promoting inflammation.

Secondary infections due to bacteria or Malassezia.

Atopic dermatitis manifests with varying levels of severity.

It can be treated and controlled. The animal does not have to suffer itching. Deterioration of its quality of life and that of its owner can be avoided by administering the appropriate treatment.

The veterinary surgeon and the dermatology specialist will help control the disease.

Vicious circle of itching Inflammation

Atopic dermatitis: inflammatory and pruritic disease

Avoid contact

+ Inflammation + Pruritus

Pruritus

Secondary infections

+ Scratching

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The disease is chronic and has a genetic component, and will therefore accompany the animal throughout its life. In dogs and cats, clinical signs worsen every year.

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CLINICAL MANIFESTATIONS AND PATHOLOGICAL PROCESSES

NODULES AND TUMOURS

53 Inflammation Skin nodules and tumours are lesions consisting of abnormal growths on the skin. They are called nodules when they are small and tumours when they are larger than 3–4 cm in diameter or affect deep planes.

Nodules and tumours are not synonymous with neoplasia

The importance of cytology ■

There are many inflammatory processes that manifest with these types of growths.

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Conditions of infectious origin: fungal or bacterial.

Conditions of parasitic origin: Leishmania, Straelensia.

Sterile processes caused by trauma, foreign bodies, or immune-mediated or reactive processes.

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Whenever these lesions are detected, cytology is required (see Sheet 9) to determine what type of cells are involved and to be able to orient the diagnosis.

The type of inflammatory cell helps to determine the cause, and sometimes even allows identification of microorganisms or parasites.

The inflammatory cells found in inflammatory reactions are neutrophils, lymphocytes, plasma cells, macrophages, and eosinophils. The cells that predominate can provide an indication of the origin of the process.

Causes of inflammation Cytology

Type of growth

Microsporum fungi

1

Staphylococcus pseudintermedius bacteria

2 3 Nodule

Trauma 1. Neutrophils: indicate an acute inflammatory process and predominate in infections.

2. Macrophages: indicate a chronic process.

3. Eosinophils: usually produced in response to arthropod bites, parasites, or allergic diseases (mainly in cats with eosinophilic granuloma complex lesions).

Leishmania

Straelensia

Immune-mediated processes Foreign bodies

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Tumour

After cytology, the veterinary surgeon may recommend additional tests such as bacterial or fungal cultures and even biopsy.

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NODULES AND TUMOURS

54 Benign skin tumours Tumours are growths produced by the uncontrolled multiplication of a cell line derived from epithelium, mesenchymal tissue, or round cells (cells of the immune system).

Cytology provides information on the cellular origin of the tumour and helps to classify it as benign or malignant.

Sebaceous hyperplasias/adenomas

Histiocytomas These are benign tumours that commonly occur in allergic puppies and dogs, and usually disappear spontaneously within 1–3 months.

■ During involution, ulceration of the surface occurs due to the inflammatory reaction that destroys the tumour.

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These are benign tumours with a pink surface that are very common in older dogs.

It is common for the same animal to develop several of these tumours.

Lipomas ■

These are growths of fatty tissue that do not usually cause problems, unless they grow to a large size or occur in areas where they interfere with movement.

■ Liposarcomas are malignant tumours of fatty tissue. It is always important to perform cytology and, in case of doubt, a biopsy.

Cysts

These are structures with an epithelium that surrounds a cavity filled with secretions, the nature of which depends on their origin: hair follicle, apocrine glands, etc.

Treatment may not be required There are benign processes that once identified by cytology can be ignored, provided they do not cause the animal discomfort or grow to a significant size.

In case of doubt, it is preferable to remove these tumours and perform a biopsy to confirm the diagnosis.

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For all other tumours, removal and a subsequent histopathological examination are always recommended to establish the diagnosis and determine whether the mass is benign or, if not, its degree of malignancy.

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PET OWNER EDUCATIONAL ATLAS. DIAGNOSIS IN DERMATOLOGY

66 Controlling pruritus Pruritus is a very unpleasant sensation that can significantly affect an animal’s quality of life. In cases of pruritus, the task of the veterinary surgeon is to identify the underlying disease and apply the appropriate treatment. In cases of intense pruritus, short-term administration of an antipruritic treatment may be necessary during the diagnostic process in order to control or temporarily diminish the itching, and thus ensure the welfare of both the animal and its owner.

The use of glucocorticoids can sometimes mask lesions or clinical signs, or alter the results of some tests necessary for the diagnosis of the underlying disease. Glucocorticoids also have both short and long-term side effects.

Other drugs are now available that do not have the side effects normally associated with corticosteroids. These are an ideal alternative for the control of pruritus during the diagnostic process as they do not mask other lesions or alter the results of diagnostic tests.

Special considerations on atopic dermatitis ■

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Atopic dermatitis usually requires antipruritic treatment both for acute outbreaks (reactive therapy) and as maintenance therapy (reactive or proactive therapy) to control the clinical signs.

Chronic antipruritic treatments are justified only in cases of atopic dermatitis, as pruritus associated with other diseases is resolved once the causative disease is controlled.

The importance of establishing a diagnosis of the underlying disease should not be underestimated.

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THERAPY

67 Long-acting antibiotics Pyodermas are bacterial infections of the skin and are very common in both dogs and cats.

Resolution requires prolonged systemic antibiotic treatment (at least 3–4 weeks).

Antibiotic treatment, once initiated, should be administered in accordance with the dose and regimen specified by a veterinary surgeon. It is very important to administer the treatment at the indicated times. Mismanagement of treatment can have devastating effects, promoting the development of bacterial resistance and hindering resolution of the infection.

Bacterial resistance is an important issue for both human and animal health, and treatment should be taken seriously and applied rigorously. Forgetting to administer one or more doses is one of the possible causes of resistance.

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14 Indications for use Some antibiotics can be given in a single injection, after which they exert their activity for 14 days. This eliminates the need to administer pills daily and ensures compliance with the regimen. These can be used, provided that the infection is sensitive to the selected antibiotic, in the following cases: ■

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When it is not possible to administer the medication continuously at the intervals specified by the veterinary surgeon.

When the patient develops a digestive disorder (e.g. vomiting, diarrhoea) during antibiotic treatment.

When oral medication is not accepted by the animal or cannot be administered by the owner, due to difficulties in handling or aggression/evasiveness on the part of the animal, etc.

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Topical treatment with antiseptic baths is a recommended complementary means of resolving bacterial skin infections.

The veterinary surgeon has the final say in prescribing medication and can select this option as long as it is appropriate both for the patient and the condition being treated.

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PET OWNER EDUCATIONAL ATLAS. DIAGNOSIS IN DERMATOLOGY

68 Treatment of atopic dermatitis 1. Control of itching and inflammation ■

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2. Treatment of the skin barrier ■

Essential in all atopic animals. It is better to treat continuously than to suspend medication and wait for a relapse (exception: seasonal allergies).

Antipruritic/anti-inflammatory drugs: glucocorticoids, oclacitinib, cyclosporine, lokivetmab.

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Repair of the skin barrier and reduction of inflammation.

Frequent baths (weekly recommended) along with the possible use of foams and pipettes that nourish, restructure, and hydrate the skin.

3. Identification and treatment of secondary infections

Control of allergic diseases may require the attention of a dermatology specialist. Collaboration between the veterinary surgeon and a specialist increases the likelihood of good results.

Detection and treatment of bacteria and Malassezia.

Pollens and other allergens

Immunotherapy Bacteria and yeast

Drugs

Therapeutic shampoo

Pruritus

4. Allergen-specific immunotherapy (ASIT) or allergy shot This is the only treatment that can reverse the disease.

Its effectiveness varies in each individual and its effect is long-term. There may be a good response in 6 months, but it may take 1–2 years before the maximum effect is observed. It is a safe treatment, which must be maintained continuously. The patient will require medication until a complete response is observed.

Efficacy of ASIT: ■ ■

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Total: the patient is free of clinical signs with ASIT only.

Partial but evaluable: ■ Medication required, but patient no longer has acute attacks throughout the year.

■ Minimal medication required. Previously allergy was not well controlled, even with medication.

Partial but difficult to evaluate: the disease remains the same, but does not become more severe.

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THERAPY

69 Referral to the dermatologist In a recent study of clients at a referral dermatology clinic, the mean duration of dermatological disease before animals were seen by the dermatology specialist was 10 months (range, 1 month to 3 years). Upon arrival, 78 % of clients reported that their animal’s disease affected their quality of life (animal or owner) and up to 72 % reported feeling anxiety, guilt, anger, or helplessness. Disease control and improved quality of life was achieved within a mean of 3 weeks after visiting the specialist. These results indicate that poorer quality of life is not due solely to disease, but also to its chronicity and a lack of adequate diagnosis and treatment.

When a patient should be referred to a specialist ■ ■ ■ ■ ■ ■ ■ ■

If there is no diagnosis.

If treatment does not provide the expected response.

If the disease is not controlled.

If the disease affects the quality of life of the patient and the owner.

If a second opinion is required.

In cases of infrequent diseases.

In cases of severe clinical presentations.

In cases of chronic diseases that are difficult to manage (e.g. atopic dermatitis), as a consultation with the specialist can help the owner understand the disease and improve the results of the treatment.

What determines the level of complexity of a case?

A specialist can easily diagnose and treat clinical cases that seem complex to the general veterinary surgeon and to the owner.

Disease

Patient

Collaboration between a generalist and a specialist is essential for the welfare of the sick animal and its owner.

Chronicity of the process

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Prompt referral can save not only money, but also, and most importantly, a lot of time and suffering.

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