Clinical Atlas of Canine and Feline Dermatology

Kimberly S. Coyner, DVM, DACVD, is a veterinary dermatologist at Dermatology Clinic for Animals in Lacey, WA and a consultant for the Veterinary Information Network.

List of contributors xv


Preface xvii


Acknowledgments xix


About the companion website xxi


1 Dermatology diagnostics 1


1.1 Skin scrapings 1


1.2 Cytology - Skin and ear 4


1.3 Cytology - Mass aspirates 6


1.4 Trichograms 8


1.5 Dermatophyte culture technique 15


1.6 Wood's lamp examination 15


1.7 Dermatophyte culture medium selection and incubation 16


1.8 Identification of dermatophytes 16


1.9 Dermatophyte PCR 18


1.10 Bacterial culture 19


1.11 Skin biopsies 19


1.12 Allergy testing 22


2 Dermatology lesions and differential diagnoses 23


2.1 Primary lesions 23


2.1.1 Macule/Patch 23


2.1.2 Papule/pustule 23


2.1.3 Plaque 26


2.1.4 Vesicle/bulla 27


2.1.5 Wheal 28


2.1.6 Nodule 29


2.1.7 Cyst 30


2.2 Primary or secondary lesions 31


2.2.1 Alopecia 31


2.2.2 Scale 34


2.2.3 Crust 35


2.2.4 Follicular cast 36


2.2.5 Comedo (Comedones) 36


2.2.6 Pigment change 37


2.3 Secondary lesions 40


2.3.1 Epidermal collarette 40


2.3.2 Scar 40


2.3.3 Excoriation 41


2.3.4 Erosion 42


2.3.5 Ulcer 42


2.3.6 Lichenification 43


2.3.7 Callus 44


2.3.8 Fissure 44


3 Lesion location and differentials 47


3.1 Face 47


3.1.1 Nasal planum 47


3.1.2 Lips/Eyelids 47


3.1.3 Muzzle 49


3.2 Ears 56


3.2.1 Pinnal margin 56


3.2.2 Pinna 57


3.2.3 Outer ear canal 57


3.3 Paws 60


3.3.1 Interdigital 60


3.3.2 Palmar metacarpal/plantar metatarsal 63


3.3.3 Paw pad 63


3.3.4 Nailbed 65


3.4 Claws 66


3.5 Perianal/perivulvar 67


3.6 Tail 68


3.7 Pressure points (elbows/hocks) 69


3.8 Trunk (dorsal and/or lateral) 70


3.9 Inguinal/axillary 78


3.10 Oral cavity 81


4 Causes and workup for pruritus in dogs and cats 85


Algorithm 4.1 Pruritic dog - Causes/Workup 86


Algorithm 4.2 Pruritic cats - Causes/Workup 87


5 Causes and workup for alopecia in dogs and cats 89


Algorithm 5.1 Canine non?inflammatory truncal alopecia - Causes/Workup 90


Algorithm 5.2 Canine multifocal alopecia - Causes/Workup 91


Algorithm 5.3 Feline alopecia - Causes/Workup 92


6 Breed?related dermatoses 93


Table 6.1 Canine breed?related dermatoses 93


Table 6.2 Feline breed?related dermatoses 107


7 Parasitic skin diseases 111


Table 7.1 Canine and feline ectoparasites 112


Demodex 112


Sarcoptes 113


Notoedres 114


Otodectes 114


Cat fur mite 114


Cheyletiella 114


Lice 115


Chiggers 115


Hookworm Dermatitis 115


Cuterebra 115


Myiasis 115


Fly bite dermatitis 116


Pelodera dermatitis 116


Dracunculiasis 116


Spider bite 116


Fleas 117


Ticks 117


Table 7.2 Flea control product options 130


Table 7.3 Tick control product options 130


8 Bacterial, fungal, oomycete, and algal infections 133


Table 8.1 Superficial bacterial skin infections 133


Impetigo 133


Pyotraumatic dermatitis 133


Intertrigo 133


Mucocutaneous pyoderma 133


Bacterial overgrowth syndrome 134


Bacterial folliculitis 134


Algorithm 8.1 Approach to chronic recurrent bacterial pyoderma 143


Table 8.2 Deep bacterial skin infections 144


Bacterial furunculosis 144


Canine acne 144


Callus furunculosis 144


Acral lick dermatitis 144


Pedal folliculitis/furunculosis 145


Post?grooming furunculosis 145


Table 8.3 Meticillin resistance 150


Table 8.4 Underlying causes for recurrent pyoderma 152


Table 8.5 Commonly used antibiotics for canine pyoderma 152


Table 8.6 Topical antibacterial products 153


Table 8.7 Subcutaneous bacterial infections 154


Subcutaneous abscess 154


Botryomycosis 155


Cellulitis 155


Necrotizing fasciitis 155


Actinomycosis 155


Nocardiosis 156


Plague 156


L?form infection 156


Table 8.8 Mycobacterial infections 159


Non?tuberculous mycobacteria 159


Feline leprosy 160


Canine leproid granuloma 160


Obligate mycobacterial infections/tuberculosis 161


Table 8.9 Yeast infections 164


Malassezia 164


Candida 165


Table 8.10 Dermatophytosis 170


Table 8.11 Environmental decontamination in dermatophytosis 180


Algorithm 8.2 Treatment of generalized dermatophytosis 181


Table 8.12 Deep fungal, oomycete, and algal infections 182


Blastomycosis 182


Cryptococcosis 182


Histoplasmosis 183


Coccidioidomycosis 184


Sporotrichosis 184


Phaeohyphomycosis 185


Pythiosis 185


Lagenidiosis 186


Zygomycosis 187


Protothecosis 187


9 Viral, rickettsial, and protozoal dermatologic diseases 199


Table 9.1 Viral dermatologic diseases 200


Feline herpesvirus dermatitis 200


Feline calicivirus dermatitis 201


Viral papillomas - Dogs/Cats 201


Cowpox virus 203


Feline infectious peritonitis (FIP) 203


Canine distemper 203


Table 9.2 Rickettsial diseases 208


Rocky Mountain Spotted Fever 208


Ehrlichiosis 208


Table 9.3 Protozoal diseases 210


Leishmaniosis 210


Toxoplasmosis 211


10 Allergic skin diseases in dogs and cats 215


Table 10.1 Hypersensitivity disorders and treatment of allergic skin diseases 216


Algorithm 10.1 Canine atopic dermatitis treatment 231


Table 10.2 Allergy treatment toolkit 232


Table 10.3 Allergy testing: Intradermal and serologic methods 235


Table 10.4 Considerations in allergen formulation 236


Table 10.5 Protocols for allergen specific immunotherapy (ASIT) 237


Table 10.6 Performing an adequate diagnostic hypoallergenic diet trial 239


Table 10.7 Feline manifestations of cutaneous allergy 244


Table 10.8 Eosinophilic granuloma complex 248


11 Autoimmune and immune?mediated dermatologic disorders 255


Table 11.1 Autoimmune and immune?mediated dermatologic disorders 256


Discoid lupus erythematosus 256


Pemphigus foliaceus 256


Pemphigus vulgaris 256


Vesicular cutaneous lupus erythematosus 257


Mucocutaneous lupus erythematosus 257


Alopecia areata 257


Uveodermatologic syndrome 257


Autoimmune subepidermal blistering diseases 258


Vasculitis 259


Post?vaccination injection site alopecia 259


Drug eruption 260


Erythema multiforme 260


Toxic epidermal necrolysis 261


Sterile panniculitis 261


Sterile granuloma/pyogranuloma 261


Juvenile cellulitis 262


Plasma cell pododermatitis 262


Pseudopelade 262


Symmetric lupoid onychitis 263


Nasal arteritis 263


Metacarpal/metatarsal fistulas 264


Canine sterile neutrophilic dermatitis (Sweet's?like syndrome) 264


Canine acute eosinophilic dermatitis with edema (Well's?like syndrome) 264


Superficial suppurative necrolytic dermatitis 265


Systemic lupus erythematosus 265


Algorithm 11.1 Treatment of canine pemphigus foliaceus 269


Algorithm 11.2 Treatment of feline pemphigus foliaceus 270


Table 11.2 Typical glucocorticoid doses for treatment of autoimmune and immune?mediated disorders 286


Table 11.3 Non?steroidal immunosuppressant or immunomodulatory drugs as adjunctive or primary treatments of autoimmune/immune?mediated diseases 287


12 Endocrine skin diseases 291


Table 12.1 Canine endocrine skin diseases 292


Hypothyroidism 292


Spontaneous hyperadrenocorticism (HAC, Cushing's disease) 292


Iatrogenic hypercortisolemia 293


Atypical Cushing's disease (ACD) 293


Food?induced Cushing's disease 293


Topical corticosteroid application 293


Pituitary dwarfism 293


Calcinosis cutis 294


Exogenous estrogen?related alopecia 294


Spontaneous hyperestrogenism 294


Spontaneous hyperandrogenism 295


Tail gland hyperplasia 295


Table 12.2 Trilostane treatment and monitoring 303


Table 12.3 Endocrine skin diseases of cats 304


Hyperthyroidism 304


Hypothyroidism 304


Hyper adrenocorticism (HAC) 304


Feline acquired skin fragility 305


Diabetes mellitus (DM) 305


Acromegaly 305


13 Non?endocrine alopecia 309


Table 13.1 Non?endocrine alopecia of dogs 310


Localized Alopecia 310


Post?clipping alopecia 310


Traction alopecia 310


Congenital follicular/ectodermal dysplasia 310


Regional to Multifocal Alopecia 310


Color dilution alopecia 310


Black hair follicular dysplasia 310


Non?color, breed?related follicular dysplasia 310


Cyclic flank alopecia 311


Pattern alopecia 311


Follicular lipidosis 311


Generalized Alopecia 311


Alopecia X 311


Anagen/telogen effluvium 312


Non?color breed?related follicular dysplasia 312


Table 13.2 Non?endocrine alopecia of cats 318


Congenital hypotrichosis 318


Hair shaft disorder of Abyssinian cats 318


Pili torti 318


Feline preauricular "alopecia" 318


Feline pinnal alopecia 318


Feline psychogenic alopecia 318


Mural folliculitis 319


Mucinotic mural folliculitis 319


Pseudopelade 319


Trichorrhexis nodosa 319


Feline paraneoplastic alopecia 319


14 Diagnosis and treatment of acute and chronic otitis 323


14.1 Approach to otitis 323


14.2 Otoscopic examination 323


14.3 Choice of otic medications 323


Algorithm 14.1 Diagnostic and treatment steps for acute otitis externa 324


14.4 Indications for systemic steroid/antibiotic therapy in otitis treatment 326


14.5 Choice of otic cleanser/flushes 326


Algorithm 14.2 Diagnostic and treatment steps for chronic otitis 327


14.6 Educate owners on how to correctly use ear flushes 328


14.7 Diagnosis and treatment of otitis media 330


14.8 When to refer for surgery 333


14.9 Ototoxicity 333


Table 14.1 Ototoxic agents 336


15 Metabolic/nutritional/keratinization dermatologic disorders 345


Table 15.1 Keratinization, metabolic, and nutritional disorders 346


Seborrhea (secondary) 346


Vitamin A responsive dermatosis 346


Sebaceous adenitis 346


Schnauzer comedo syndrome 347


Nasodigital hyperkeratosis 348


Callus 348


Xeromycteria 349


Ear margin dermatosis 349


Canine acne 349


Feline acne 350


Zinc responsive dermatosis 350


Necrolytic migratory erythema 351


Exfoliative dermatitis associated with thymoma 351


Xanthomas 352


Split paw pad disease 352


16 Congenital/hereditary dermatologic disorders 363


Table 16.1 Congenital/hereditary dermatologic disorders 364


Primary seborrhea 364


Idiopathic facial dermatitis of Persian and Himalayan cats 364


Ichthyosis 365


Nasal parakeratosis of Labrador Retrievers 365


Dermatomyositis 365


Congenital alopecia 366


Cutaneous asthenia (Ehlers Danlos) 366


Mucinosis 366


Urticaria pigmentosa 367


Ulcerative nasal dermatitis of Bengal cats 367


Dermoid sinus 367


Acrodermatitis 367


Acral mutilation syndrome 368


Congenital keratoconjunctivitis sicca (KCS) and ichthyosiform dermatosis in the Cavalier King Charles Spaniel (CKCS) 368


Exfoliative cutaneous lupus erythematous 368


Epidermolysis bullosa 368


17 Pigmentary dermatologic disorders 375


Table 17.1 Pigmentary dermatologic disorders 376


Lentigo 376


Acquired hormone?associated 376


Acquired post?inflammatory hyperpigmentation 376


Vitiligo 377


Nasal hypopigmentation "snow nose" 377


Nasal hypopigmentation "Dudley nose" 377


Acquired aurotrichia 377


"Dalmatian bronzing" syndrome 377


18 Environmental skin disorders 385


Table 18.1 Environmental skin disorders 386


Solar dermatitis 386


Burns 387


Radiant heat dermatitis 389


Frostbite 389


Irritant contact dermatitis (ICD) 389


Grass awns/burs 390


Post traumatic alopecia 390


Hygroma 391


Pressure sore 391


19 Skin tumors 401


Table 19.1 Benign and malignant skin tumors in dogs and cats 402


Squamous cell carcinoma (SCC) 402


Bowenoid in situ carcinoma 402


Basal cell carcinoma 403


Sebaceous gland tumors 403


Follicular tumors 404


Dilated pore of Winer 405


Follicular cyst 405


Cutaneous horn 405


Apocrine gland tumors 406


Feline ceruminous (apocrine) cystomatosis 407


Perianal gland tumors 407


Apocrine gland tumors of anal sac origin 407


Lipoma 408


Infiltrative lipomas 408


Liposarcoma 408


Mast cell tumor 409


Fibroma 409


Dermatofibroma 409


Nodular dermatofibrosis 410


Acrochordon 410


Mammary tumors 410


Hemangioma 411


Hemangiosarcoma 412


Cutaneous progressive angiomatosis 412


Hemangiopericytoma 413


Lymphangioma 413


Lymphangiosarcoma 413


Fibrosarcoma 413


Cutaneous epitheliotropic lymphoma 414


Cutaneous non?epitheliotropic lymphoma 415


Feline cutaneous lymphocytosis 415


Plasmacytoma 415


Melanocytoma 416


Malignant melanoma 416


Canine cutaneous histiocytoma 417


Canine reactive cutaneous histiocytosis 417


Canine systemic histiocytosis 417


Feline progressive histiocytosis 417


Canine cutaneous langerhans cell histiocytosis 418


Collagenous hamartoma 418


Calcinosis circumscripta 418


Transmissible venereal tumor 419


Feline lung?digit syndrome 419


20 Dermatology formulary 453


Table 20.1 Systemic antibiotics 454


Table 20.2 Systemic antifungals 458


Table 20.3 Systemic antiviral/antiprotozoal medications 459


Table 20.4 Antihistamines 459


Table 20.5 Systemic glucocorticoids 461


Table 20.6 Non?steroidal immunomodulating and immunosuppressive drugs 463


Table 20.7 Behavior modifying medications/analgesics 467


Table 20.8 Systemic antiparasitic drugs 468


Table 20.9 Topical antiparasitics 470


Table 20.10 Nutritional supplements/vitamins/retinoids 471


Table 20.11 Non?glucocorticoid hormones 472


Table 20.12 Topical non?steroidal antipruritic therapies 474


Table 20.13 Topical glucocorticoids 475


Table 20.14 Topical antimicrobials/otics 475


Table 20.15 Topical antiseborrheics 477


Table 20.16 Topical immunomodulators and retinoids 477


Index 479