Dermatology 3 Flashcards
Approach to pustule, papule, scale and crust,
What history is needed when working up a case presented for pustules/papules/scale/crust?
- Breed, age of onset
- In contacts/human affected
- Pruritus presence/abscence, severity,before or after lesion)
- Course of disease
- Seasonality
- Response to past treatment incl, parasiticides
- Results of prior tests
- Concurrent systemic signs
- Travel abroad
In what conditions is pyoderma of the face more likely to occur?
- Autoimmune
- Drematophytosis
- Chronic disease
In which conditions are large, green pustules more common?
Pemphigus and HAC
What would pustular lesions that come in waves be suggestive of?
Pemphigus
Explain the importance of determining the variety of lesions present (early vs late)
- Mixture of pustules at different stages suggests bacterial pyoderma
- If all are at the same stage, more suggestive of pemphigus
What diagnostic tests should be carried out when investigating pustules/papules/crusts/scale?
- Tests for ectoparasites, dermatophytosis
- Stained acetate tape strips, impression smears for cytology
- Cytology of fresh pustule contents if available
- +/- bacterial culture/sensitivity testing
If you have no strong suspicion of pemphigus foliaceous, what investigation plan should be followed?
- Thorough parasite control program, including treatment for sarcoptic mange and fleas
- Eliminate secondary infection (bacterial pyoderma/Malassezia dermatitis)
- Re-evaluate after 3-6 weeks
If you have a strong suspicion of pemphigus foliaceous, what investigation plan should be followed?
Eliminate secondary microbial infection then biopsy
If, following treatment for microbial infection and ectoparasites, the pustules/papules have resolved but the animal is still pruritic, what would be the next approach?
Work up as for hypersensitivities
If, following treatment for microbial infection and ectoparasites, the pustules/papules have resolved but there is rapid relapse, what would be the next approach?
- Consider if: initialtherapy too short, owner compliance, adequate antibiotic dose
- Check re. underlying health/endocrine/metabolic disease
- If all normal, consider primary bacterial pyoderma, although likely to have unidentified underlying cause
If, following treatment for microbial infection and ectoparasites, the pustules/papules have not changed or are worse, what would be the next approach?
- repeat skin scrapings re. Demodex
- Repeat impression smears
- Culture intact pustule (resistance)
- Biopsy (pemphigus foliaceous)
- Serum biochem, haematology, urinalysis (systemic disease)
What is scale caused by?
Hyperkeratosis, due to increased or disrupted epidermal turnover, leading to increased depth of cornified layer
What are the 2 types of scale?
Parakeratotic and orthokeratotic
Describe parakeratotic hyperkeratosis (appearance and cause)
- Cells have nuclei
- May be inflammation and high turnover of epidermis e.g. Malassezia dermatitis, zinc responsive deramtosis, superficial necrolytic dermatitis
Describe orthokeratotic hyperkeratosis (appearance and cause)
- Increase in normal keratinocytes
- Common inflammatory disorders, keratinisation disorders
- No nuclei
What are crusts often associated with?
- Surface squames, hair, topical medications
- scaling
- Pustular diseases
- Ulcerative diseases
Why should steroids not be used in the treatment of crusts prior to diagnosis?
Need to see if lesions are pruritic following treatment for ectoparasites and microbial infections
Outline the diagnostic approach to scaling or crusting
- History, signalment, general/derm examination
- Rule out ectoparasites using routine tests, treatment trials
- rule out microbial infection using cytology, cultures, response to treatment
- If lesions remain, are they pruritic?
If crusting or scaling lesions are pruritic following treatment for ectoparasites and microbial infection, what are the next steps?
- Exclusion diet trial
- If effective, is food induced atopy
- If negative, probably environmental atopy, but biopsy if clinical signs do not fit
If crusting or scaling lesions are not pruritic following treatment for ectoparasites and microbial infection, what are the next steps?
- Evaluate for metabolic/endocrine disease
- If positive, may be hypoT, HAC, sex/adrenal hormone imbalance, DM, superficial necrolytic dermatitis
- If negative, biopsy
If there is no evidence of metabolic or endocrine disease in the investigation of crusting or scaling lesions that are not pruritc following ectoparasite and microbial infection treatment trials, what conditions may be found on biopsy?
- Primary keratinisation disorders
- Neoplasia: cutaneous lymphoma, paraneoplastic syndromes
- Immune mediate: pemphigus, lupus
- Nutritional: zinc-responsive dermatosis, EFA deficiency, generic dog food disease
- Other underlying disorders: Leishmaniasis, FeLV, FIV, superficial necrolytic dermatitis, adverse drug reactions
What are primary keratinisation disorders?
- The only primary causes of scale
- Defects in normal keratinisation process
- Either due to abnormal formation of keratinocytes, or abnormal sebaceous gland function
Describe the occurrence, diagnosis and treatment of primary keratinisation disorders
- Rare
- Often breed related and occur in younger animals (genetic)
- Diagnosis by exclusion
- Treat symptomatically, care not to miss other disorders that can be cured
List the primary keratinisation disorders of dogs
- Primary idiopathic keratinisation disorder (“idioathic seborrhoea”)
- Nasodigital hyperkeratosis
- Icthyosis
- Vitamin-A responsive dermatosis
- Schnauzer comedo syndrome
- Ear margin dermatosis
- Footpad hyperkeratosis
Which breeds are predisposed to primary idiopathic keratinisation disorder?
- Cocker/Springer spaniels
- Irish setter
- Basset
- Sharp-pei
- Doberman
- WHWT
- GSD
Which breeds are predisposed to nasodigital hyperkeratosis?
- Cocker/English springer spaniels
- Old dogs of any breed, more commonly related to age
Which breeds are predisposed to ichthyosis?
- WHWT
- Golden retrieer
Which breeds are predisposed to Vitamin-A responsive dermatosis?
Cocker spaniels
Which breeds are predisposed to Ear Margin Dermatosis?
- Dachshund
- Doberman
- Short-haired breeds
Which breeds are predisposed to Footpad hyperkeratosis?
- Irish terrier
- Dogue de Bordeaux
Describe the appearne of primary idiopathic keratinisation disorder in spaniels and other breeds
- Scaling, often thick and adherent
- Erythema, greasy scale of lips, periocular skin, ventral neck/body, feet, tail
- Often otitis externa
- Secondary pyoderma and Malassezia dermatitis common
- Can appear similar to allergic animal
- Other breeds often dry truncal scale
Describe the appearance of ichthyosis in Golden retrievers
- Fish scale appearance
- Often young dogs, no other clinical signs unless secondarily infected
Describe the appearance of nasodigital hyperkeratosis
Frond like hyperkeratosis that may fissure and become infected
What is the key part of treatment for nasodigital hyperkeratosis?
Need to stop foot pad fissuring
- Warm water soaks (warm damp flannel held against lesion),
- Topical salicylic acid
- Poprylene glucol
- 0.5% tretinoin
What conditions can nasodigital hyperkeratosis develop secondary to?
- HypoT
- Pemphigus foliaceous
- Cutaenous lupus
- Necrolytic Migratory Erythema (MNE)
- Distemper
- ZN-responsive dermatosis
What are calluses and how do they develop? What is the main concern with these?
- Areas of hyperkeratosis and acanthosis
- Develop on bony prominences in heavy dogs on hard surfaces, normal protection mechanism
- Usually no concern but may fissure and become infected
Describe the treatment for calluses
- Do not excise, will not heal due to pressure that caused initial lesion
- Warm water soaks, topical salicylic acid, propylene glycol, o.5% tretinoin
- Control infection if present
- Encourage lying on soft bedding
List primary keratinisation disorders of cats
- Stud tail/tail gland hyperplasia
- Feline ace
- Fleine seborrhoea
- Idiopathic facial dermatitis
- Sebaceous adenitis
Describe the predisposition, appearance and treatment of stud tail in cats
- Entire males mainly
- Greasy, scaly tail
- Neutering is treatment
Which breeds are predisposed to feline seborrhoea?
- Persian
- Himalayan
- Exotic short-haired