Canine and feline dermatology atlas

Gustavo Machicote Each chapter also provides a brief summary of the aetiopathogenesis of the lesions, the clinical features and the diagnostic method, and lists the main differential diagnoses and treatment options.

This book will undoubtedly help the clinician develop a good “clinical eye”.

CANINE AND FELINE DERMATOLOGY ATLAS

For the clinician, having pictures of the diseases that may be encountered in daily practice is very helpful when it comes to making a diagnosis. Dermatology is no exception, but perhaps one of the specialties where this is most needed. This atlas contains a large collection of pictures of the most common skin diseases in dogs and cats, showing not just the typical appearance of each condition, but also dermatological cases that do not follow the “classical pattern”. The aim is to help the veterinary surgeon reach the right diagnosis in atypical cases.

Canine and Feline

DERMATOLOGY ATLAS Gustavo Machicote Goth

Canine and Feline Dermatology Atlas

Introduction Diagnosis in dermatology is based mainly on recognising lesions and knowing why they arise, i.e. their aetiopathogenesis.

This means that visual inspection of the clinical features can be fundamental, and in most cases, together with a good case history, will enable a list to be drawn up of the most likely diagnoses consistent with the disease, i.e. differential diagnoses.

The veterinary surgeon’s expertise, based on a good memory for images and skilful questioning of the owner, can lengthen or shorten this list.

In dermatology, it is very important to recognise the primary and secondary lesions, found individually or together, that determine the gross clinical features of the disease. By way of revision in this introductory chapter, these are:

Primary lesions

y y y y y y y y y

Macule Papule Plaque Pustule Vesicle Nodule Tumour Cyst Wheal

Secondary lesions

y y y y y y y y y y y y

Scale Crust Scar Erosion Epidermal collarette Ulcer Comedo Fissure Excoriation Lichenification Hyper/hypopigmentation Callus (hyperkeratosis)

These lesions may occur in combination, producing the clinical patterns that, associated with a certain distribution on the animal’s body and to specific symptoms, can result in the clinical features of each dermatological disease.

2

01

Introduction to diagnosis in dermatology

Clinical patterns Great caution is required when thinking that a clinical picture or set of clinical features might be pathognomonic. This is seldom true in dermatology. Instead, it is the protocol and diagnostic tests that enable a correct diagnosis to be made.

The classical clinical patterns of most skin diseases can be divided into:

Clinical patterns of skin diseases

y y y y y y

01

Alopecic (focal, multifocal, regional, generalised, diffuse, symmetrical) (Figs. 16).

Erosive/ulcerative due to progression of primary lesions or self-inflicted (Fig. 7).

Exfoliative, desquamative, seborrhoeic or a combination (Fig. 8).

Papulo/pustulocrustous due to normal progression of primary lesions (Fig. 9).

Nodular due to developmental, inflammatory or neoplastic abnormalities (Fig. 10).

Pigmentary changes due to stimulation or suppression of melanocytes (Fig. 11).

Focal alopecic pattern. Dog with seborrhoeic plaque on the dorsum of the tail.

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Canine and Feline Dermatology Atlas

01

Generalised dermatophytosis in a Miniature Pinscher.

02

Classical rings on the ventrum of a puppy.

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03

Fungal dermatoses

03

Typical appearance of a dermatophytic kerion.

05 Trichophyton

disease of the bridge of the nose.

45

04

Dog with multiple kerions.

Canine and Feline Dermatology Atlas

Systemic mycoses Aetiopathogenesis of lesions and description of clinical features These are mycoses caused by saprophytic fungi found in soil and vegetation that can affect various organs and spread via the bloodstream to the skin in dogs and cats.

These infections are caused by Blastomyces dermatitidis, Coccidioides, Cryptococcus and Histoplasma.

The lesions tend to be characterised by granuloma formation and general illness of the animal.

Diagnostic method The clinical appearance, cytology, histopathology, and a case history linking the animal to endemic areas are fundamental.

Main differential diagnoses y Granulomas or pyogranulomas of various origins; y Neoplasms.

Treatment Azole derivatives (itraconazole, fluconazole, ketoconazole) tend to be used, although amphotericin B may be necessary in some refractory cases.

12

Skin lesion in a lateral site in a cat with Cryptococcus neoformans disease.

Image courtesy of Didier Carlotti.

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03

Fungal dermatoses

13

Close-up of the skin lesion in the cat seen in the preceding figure. Image courtesy of Didier Carlotti.

14

Fine-needle aspiration cytology from nodules in the cat seen in Figure 12, showing fungi as spherical bodies surrounded by a thick capsule (Diff-Quick, Ă—1000). Image courtesy of Didier Carlotti.

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Canine and Feline Dermatology Atlas

01

Oedema and erythema of the muzzle in a Shar Pei puppy with angio-oedema.

02

Urticaria with classical wheal formation all over the body. Note the coat abnormalities.

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06

Allergic dermatoses

Atopy and adverse food reaction Aetiopathogenesis of lesions and description of clinical features Both kinds of type I hypersensitivity reaction are included in the same description because, from a dermatological point of view, they both produce atopic dermatitis. This is a clinical picture characterised by essential pruritus, with no lesions, which then progresses to secondary lesions and becomes chronic, due to excoriations and opportunistic bacterial and yeast infections. Different regions of the body may be affected in different breeds, but involvement of the feet, axillae and groin, head, and periocular and perioral areas is common.

Recurrent otitis is also frequently seen.

The condition usually progresses from erythema to papules/pustules and crusts, and then tends towards lichenification, hyperpigmentation and seborrhoea.

At present, this disease is somewhat better defined in dogs than in cats. In cats, it is now more correct to talk of feline hypersensitivity related to environmental allergens, food or fleas, and the reaction patterns typical of this species tend to occur, such as miliary dermatitis, erosion and ulceration of the face and neck, eosinophilic reactions and symmetrical alopecia.

Diagnostic method These diseases are diagnosed mainly from a clinical perspective. Several criteria must be met in order for them to be diagnosed. The origin of the atopic dermatitis, whether it is caused by environmental or food allergens, can be distinguished by starting an elimination diet. Serological or intradermal reaction tests can then be done to determine the environmental allergens involved. Some clinically atopic cases test negative by serology or intradermal reaction. This condition is defined as atopic-like dermatitis. Serological tests for food allergens can have good negative predictive ability, which is useful for designing elimination diets.

Main differential diagnoses y Sarcoptic mange; y Flea bite allergy; y Primary seborrhoea; y Dermatophytosis (mainly in cats).

Treatment The only really curative treatment is based on immunotherapy aimed at desensitising the animal. Symptoms can also be controlled using ciclosporin, corticosteroids, a good diet rich in omega 3 fatty acids, and antiseptic shampoo therapy. The use of products based on lipid complexes and phytosphingosines by the topical route can be very important for improving the quality of the ground substance. If food allergens are implicated they must be avoided.

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Canine and Feline Dermatology Atlas

02

Lipoma cytology.

03

Liposarcoma cytology.

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10

Most common neoplasms

Mastocytoma Aetiopathogenesis of lesions and description of clinical features These neoplasms, which are much more common in dogs than in cats, are composed of mast cells that proliferate in an uncontrolled fashion. Their degree of malignancy is highly variable in dogs, whereas in cats they are usually benign.

Some dog breeds are somewhat predisposed to cutaneous mastocytoma, e.g. Boxer, Staffordshire Bull Terrier, Labrador, Boston Terrier and Bull Terrier. The clinical presentation is too variable to describe because it can assume a wide range of appearances.

Diagnosis Clinically, its appearance is never diagnostic. However, its sudden change in size and the pruritus induced when inflammatory mediators are released (known as Darier’s sign) can be diagnostic.

Main differential diagnoses y Various neoplasms; y Abscesses; y Cysts.

Treatment Radical surgery tends to be the best treatment whenever possible. Depending on the grade and stage of the tumour, cancer therapies such as lomustine, tyrosine kinase inhibitors, corticosteroids and vinblastine can be used.

04

Scrotal mastocytoma, fairly common in Boxer.

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Canine and Feline Dermatology Atlas

15

Ventral appearance of the cat with paraneoplastic alopecia. Image courtesy of Didier Carlotti.

16

Close-up of the patient’s ventral skin. Image courtesy of Didier Carlotti.

17

18

Facial appearance of the cat with paraneoplastic alopecia.

Image courtesy of Didier Carlotti.

194

Histopathology of the patient with paraneoplastic alopecia, showing epidermal hyperplasia with absence of the stratum corneum and follicular atrophy.

Image courtesy of Didier Carlotti.

10

Most common neoplasms

Hepatoid gland adenoma/carcinoma Aetiopathogenesis of lesions and description of clinical features These neoplasms of the perianal or hepatoid glands generally tend to affect dogs over 8 years old. The majority are benign, and they are intimately related to the influence of androgens. Adenocarcinomas occur in a clinically similar manner, which makes them macroscopically indistinguishable. The tumours are generally of irregular shape and tend to occur in the perianal or perigenital areas, or at the base of the tail.

Diagnosis The diagnosis is obtained from the clinical appearance, cytology and a biopsy.

Main differential diagnoses y Other neoplasms; y Anal sac disease; y Perianal fistulas.

Treatment In cases of adenomas, neutering tends to provide a solution. If surgery cannot be performed, anti-androgens, e.g. deslorelin implants, can be used. Adenocarcinomas carry a worse prognosis and should be treated surgically very early in order to achieve any success.

19

Appearance of a hepatoid gland adenoma in a 9-year-old Pit Bull.

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