Introduction to Dermatology Flashcards
What is the biggest dermatological problem in Cats/ Dogs?
Cats = Swellings
Dogs = Pruritus
What are the most common causes of dermatological problems in dogs/cats?
Dogs = Bacterial infection, Parasitic, Neoplastic
Cats = Bacterial infection + Parasitic
What are the common pitfalls with dermatology?
- Disregarding history
- Failure to appreciate clinical signs
- Not taking a logical, problem oriented approach
- Errors in taking diagnostic samples
- Errors in allergy testing (it is not a diagnostic test)
- Errors in interpreting results
- Errors in therapy
What is the plan for dermatology consultation?
- History
- Examination
- List differentials
- Plan investigation
How can you save time during consultation?
Take history whilst doing physical exam
What are the likely to be the dermatological cause in very young animals (<1 year)?
- parasites
- congenital
- food-induced atopic dermatitis
What are the likely to be the dermatological cause in adult animals?
- immune mediated
- endocrine
- food-induced atopic dermatitis
What are the likely to be the dermatological cause in elderly animals?
- neoplastic
- metabolic
- food-induced atopic dermatitis
What are west highland white terriers more susceptible of getting?
Atopic dermatitis
What can male animals get?
Sertoli cell tumour
Why does the colour of the animal predispose them?
*Squamous cell carcinoma
- Spontaneous forms
- oral
- ungual
- UV induced
- de-pigmented skin
- white hair-coat
- sparsely haired regions
What are general questions you could ask all patients?
- attitude and exercise tolerance?
- appetite and thirst?
- vomiting or diarrhoea?
Relating to complaint:
* number of stools per day?
* sneezing or conjunctivitis?
* seasonal history?
* neurological signs?
* drug history?
What are the possible causes of chronic dermatological problem?
- allergy
- metabolic
- endocrine
- neoplastic
What are the possible causes of acute dermatological problem?
- parasites
- infectious
- immune-mediated
- hypersensitivity
What is an itch that rashes?
Atopic dermatitis - everything else is a rash that itches
What is more likely to be a problem in late summer - autumn?
- harvest mites
- cow pox virus
What is more likely to be a problem in spring-summer?
Atopic dermatitis
Why should you ask about previous/current treatments?
Improved/ no change/ worse
Adverse effects
What are the potential risks if the animal has travelled abroad or was a rescue?
- leishmaniasis
*babesia
*erhlichia
*dirofilaria
What are the possible parasitic contagions?
*Flea bites
*Sarcoptic mange
*Cheyletiellosis
What is a infectious contagion?
*Dermatophytosis
What is the morphology of primary/secondary lesions?
Primary
* initial eruption develops spontaneously due to underlying disease e.g., papule or pustule
* usually transient
* sample to aid diagnosis
Secondary
* evolve from primary lesions or external factors e.g., crust evolves from a pustule
* may help with diagnosis
Some lesions can be either 1 or 2
* e.g., alopecia is 2 if due to self-trauma or 1 if due to endocrinopathy
* Skin disease is continually evolving
* a mixture of primary and secondary lesions
How many layers does the epidermis have?
4
What is within the dermis?
- blood vessels & nerves
- hair follicles
- sebaceous glands
- sweat glands
What are primary lesions?
- Pustule
- Papules and pustules
- Papular-macular rash
- Pigmented macules
- Alopecia (demodex)
- Erythematous plaques and papules
- Alopecia (seasonal flank alopecia)
- Vesicle
What are secondary lesions?
- Lichenification
- Thinned skin (HCA; also calcinosis cutis plaques)
- Crusts and erosions
- Excoriations/ erosions
- Epidermal collarettes
- Scale (secondary to chronic inflammation)
- Ulcers
- Comedones +++ and an erosion
What lesion causes thickening of all skin layers due to chronic inflammation?
*lichenification
What lesion causes loss of epidermis above basement membrane?
*Erosions
What lesion causes loss of epidermis through the basement membrane into the dermis?
*Ulcers
Where does cheyletielliosis tend to infect?
Dorsum
Where does sarcoptic mange tend to infect?
Ears
Elbows
Ventral surface
Where does atopic dermatitis tend to infect?
Ears
Paws
Face / muzzle
Where does Flea Allergic Dermatitis tend to infect?
Perianal area
Caudal dorsum
What type of dermatology problem comes and goes? (Waxing & waning)
*Allergic
*Immune-mediated
What dermatological problems are progressive?
*Metabolic
*Endocrine
*Neoplastic
What dermatological problems are intermittent?
*Parasites
*Infections
What are the major presenting signs?
*Pruritus
*Alopecia
*Crusting
*Scaling
*Nodules
What are 2ndry skin infections more common in?
Dogs> Cats
What is the most common feline infection?
Cat bite abscess
What are primary infections more common in? (Dermatophytosis/viral)
Cats>dogs
What are endocrinopathies and neoplasia more common in?
Dogs> cats
What is the most common cause of alopecia in cats?
*usually due to self-trauma - pruritus
What are the pruritus differentials in dogs?
- Atopic dermatitis
- Flea allergic dermatitis
- Parasites
- Infections e.g., Malassezia and bacterial pyoderma (secondary)
- Contact allergy
- Cutaneous lymphoma
- Pemphigus foliaceus
What are the pruritus differentials in cats?
- Feline atopic skin syndrome
- Flea allergic dermatitis
- Parasites
- Infections e.g., dermatophytosis (primary)
- Contact allergy
- Cutaneous lymphoma
- Pemphigus foliaceus
How would you exclude pruritus differentials?
*History
*Clinical signs
*Diagnostic tests
What other clinical signs may pruritus lead to?
- Alopecia
- Erythema
- Hyperpigmentation
- Lichenification
- Excoriations
- erosions and/or ulcers
- Secondary infections = papules, pustules, crusts, scales, epidermal collarettes, macular hyperpigmentation
What are the spontaneous inflammatory alopecia differentials in dogs?
- Bacterial folliculitis
- Demodicosis
- Dermatophytosis
- IMD of hair or skin
What are the spontaneous inflammatory alopecia differentials in cats?
- Bacterial folliculitis
- Demodicosis
- Dermatophytosis
What are the spontaneous non-inflammatory alopecia differentials in dogs?
- Endocrine
- Seasonal flank alopecia, Effluvium,
dysplasias, Pattern baldness, Alopecia X, congenital, etc.,
What are the spontaneous non-inflammatory alopecia differentials in cats?
- Endocrine (RARE)
- Paraneoplastic syndrome (RARE)
- Effluvium, dysplasias, congenital
What are the primary scaling differentials in dogs?
- Canine ear margin seborrhoea
- Ichthyosis
- Primary seborrhoea
- Zinc responsive dermatosis
What are the primary scaling differentials in cats?
- Feline acne
- Ichthyosis
- Primary seborrhoea
What are the secondary scaling differentials in dogs?
- Active inflammation (allergy, parasites, bacterial infection, dermatophytosis)
- almost any resolving inflammatory dermatosis
- Endocrine
- Epitheliotropic lymphoma
- Leishmaniasis
What are the secondary scaling differentials in cats?
- Active inflammation
- Diabetes mellitus
- Idiopathic facial dermatitis of cats (‘dirty face’ in Persian cats)
- Epitheliotropic lymphoma
- Feline thymoma-associated exfoliative dermatitis
- FeLV/FIV dermatosis
What are the differentials for crusting from pustules in dogs/cats?
Infections
* Superficial bacterial pyoderma
Immune-mediated disease
* Pemphigus foliaceus
What are the differentials for crusting from erosions/ulcers in dogs?
Immune mediated
* Erythema multiforme
* Vasculitis/ vasculopathy
* Cutaneous/systemic lupus erythematosus
Metabolic disease
* Superficial necrolytic dermatitis (hepatocutaneous syndrome)
Deep microbial infections
What are the differentials for crusting from erosions/ulcers in cats?
Allergy
* Head and neck pruritus and miliary dermatitis
* See feline CRP lecture
* Mosquito-bite hypersensitivity
Deep microbial infections
* Atypical bacteria, fungi, viruses (pox, herpes)
What are the differentials for nodules in dogs?
Neoplasia
Infectious
* Acid-fast bacteria, fungal, viral
Inflammatory
* Urticaria/angioedema
* Interdigital cysts
Immune-mediated
* Histiocytic, pyogranuloma-granuloma, panniculitis
What are the differentials for nodules in cats?
Neoplasia
Infectious
* Acid-fast bacteria, fungal, viral
Inflammatory
* Eosinophilic granuloma complex
* Urticaria/angioedema
Immune-mediated
* Feline plasma cell pododermatitis
What diagnostic tests can be taken for skin cytology?
- Direct impression smear
- Indirect impression smear
- Tape strip
- Fine needle aspirate (FNA)
What diagnostic tests can be taken for parasites?
- Brushings
- Tape strips
- Hair plucks (trichograms)
- Skin scrapes - superficial and or deep
What are the possible sampling methods for alopecia?
- Hair pluck (trichogram) - Look at hair and for parasites
- Skin scrape for parasites
- Cytology for pyoderma
- Culture for dermatophytes
- Biopsy
What are the possible sampling methods for scale?
- Coat brushings
- Acetate strip =
-Unstained for parasites
-Stained for infections - Hair pluck
- Skin scrape
- Biopsy
What are the possible sampling methods for nodules?
*FNA
*Biopsy
What are the possible sampling methods for crusts?
- Skin scrapes
- Lift crust and perform direct
impression smear - Biopsy
What are the presenting signs of demodex?
- Alopecia
- Variable pruritus
- Scale (follicular casts)
- +/- secondary bacterial
infection =
-crusts if superficial
-nodules if deep
What are the presenting signs of sarcoptic mange?
- Crusts +++
- Usually severely pruritic
(hypersensitivity) - Self-trauma causing alopecia
What are the presenting signs of cheyletiella?
- Scale +++
- Variable pruritus
- Self-trauma causing alopecia
How would you diagnose ectoparasites?
For surface parasites
e.g., fleas, lice, ticks, harvest mites, Cheyletiella and Demodex gatoi
* Coat brushings
* Flea comb wet paper test
* Sellotape impression
For shallow and surface mites living in the epidermis
e.g., Cheyletiella, Demodex gatoi, Sarcoptes scabei and Notoedres cati
* Superficial skin scrapes
For deeper mites
* Deep skin scrapes
* Hair plucks
* Biopsy
What ectoparasite lives deepest in the skin?
*Demodex - within hair follice
