Crusting disease Flashcards
What is a crust?
= dried exudate, containing blood/serum/scales/pus
- colloquially a ‘scab’
- occasionally a Primary lesion
- usually a secondary lesion, e.g. to scaling dz, pustular dz, ulcerative dz
- very common but usually not diagnostically helpful in isolation
What is the most common cause of crusts in dog?
- superficial pyoderma
What to do when see a crust?
- First step usually:
– Rule out ectoparasites: routine tests (e.g. skin scrapes, combing, trichogram) + treatment trial
– Rule out microbial infections
-> Bacterial pyoderma: cytology – of primary lesion, if possible, otherwise impression smear from skin under crust
-> Dermatophytosis (esp cat): Wood’s lamp, dermatophyte culture - Then further investigations if lesions remain, especially biopsy
– NB biopsy most likely to be diagnostic if secondary infections cleared first
– Don’t dislodge crust! - trim hair with scissors but otherwise no prep
– Request special stains, esp re microorganisms
Diseases presenting primarily as crusting
- Pemphigus foliaceous
- Canine juvenile sterile granulomatous dermatitis and lymphadenitis (‘juvenile cellulitis’, ‘puppy strangles’)
- Squamous cell carcinoma/ solar dermatitis
- Feline acne
- Calcinosis cutis
- Superficial necrolytic dermatitis (‘hepatocutaneous syndrome’)
- Facial dermatitis of Persians
Canine pemphigus foliaceous
- Most common autoimmune skin disease in dog
- Middle aged to older dogs (but can occur at any age)
- ?male > female
- Strong breed predisposition (Akita, Chows, Cocker spaniels, Dachshunds, Labradors, English bulldog & Shetland sheepdog)
Pathogenesis of canine pemphigus foliaceous
- Auto-immune (mainly IgG) response to desmosomal proteins, especially desmocollin 1
– Mainly expressed in superficial layers of epidermis so lesions fairly superficial - Trigger? Usually idiopathic. Occasionally drugs, ?UV
Cytology of pemphigus foliaceous
- Acantholytic keratinocytes (large ‘fried-egg’ cells, sometimes in rafts) + neutrophils
How are the pustules in pemphigus foliaceous different to pustules in pyoderma?
- Often larger and with erythematous margins
- Distribution – often includes face/pinnae/footpads
- Lesions bilaterally symmetrical
– But the pustule is transient so usually see crusts/erosions
Canine pemphigus foliaceous clinical signs
- Usually presents as bilaterally symmetrical crusting disease
- Lesions can occur anywhere, but head/pinnae involved in 80% cases
- +/- pruritus
- +/- mildly unwell/pyrexic
- Secondary pyoderma common and confusing
-> partial response to treatment of pyoderma - NB if pyoderma unresponsive to rational treatment, PF is a d/d!
Canine pemphigus foliaceous tx
- Induction:
– Immunosuppressive doses of systemic GCC, usually prednisolone – rapid action
– +/- topical GCC
– Treat till most lesions healed and no new lesions for 10 days - Titration:
– Taper SLOWLY to lowest effective maintenance dose, q48h if possible - +/- adjunctive immunosuppressive agent – to help minimise steroid dose, e.g.
– Chlorambucil
– Ciclosporin/ tacrolimus
– Azathioprine
– Mycophenolate mofetil
– NB many slow (e.g. 4 weeks) to take effect, so may give alongside steroids from onset
Canine pemphigus foliaceous prognosis
- Often poor due to adverse effects of treatments
Feline pemphigus foliaceous
- Less common than canine PF
- Wide range of age of onset
- Clinical signs: as dog, but also claw folds affected in 30% cases and skin around nipples (areolar skin)
– caseous claw fold exudate ‘Philadelphia feet”
Feline pemphigus foliaceous diagnosis, tx + prognosis
- As for dog except:
– Occasionally oral dexamethasone (off label) in place of prednisolone
– +/- adjunctive treatments
->Chlorambucil (NB NOT AZATHIOPRINE for cats!)
->Ciclosporin, topical steroids - Monitor fructosamine on steroids?
- Prognosis better than dog
Canine juvenile sterile granulomatous dermatitis and lymphadenitis
- Sterile granulomatous condition affecting face, pinnae, ears and submandibular lymph nodes
- Aetiology unknown: immune dysfunction?
- Breeds: esp Golden/Labrador retrievers, Daxis
- Age: usually puppies, occasionally adults
Canine juvenile sterile granulomatous dermatitis and lymphadenitis clinical signs
- Sterile pustules -> ulcers/draining tracts/crusts/hair loss and cellulitis affecting above areas
- Acute swelling of muzzle, lips, eyelids (d/d angio-oedema)**
- Marked submandibular lymphadenopathy**
- Rarely nodules at other sites
- +/- otitis externa
- +/- pyrexia, depression, anorexia, joint pain
Canine juvenile sterile granulomatous dermatitis and lymphadenitis diagnosis
- Signalment, history, clinical signs very suggestive
- Important to rule out other conditions that may cause cellulitis: demodicosis, infections (bacterial pyoderma, dermatophytosis)
->NB on cytology - pyogranulomatous and apparently sterile inflammation (doesn’t rule out pyoderma) - Biopsy confirmatory – send for histopathology and tissue culture
Canine juvenile sterile granulomatous dermatitis and lymphadenitis tx
- Prednisolone (immunosuppressive doses) to resolution (7-14 days?), then taper slowly to withdraw
- +/- other immunosuppressive agents, e.g. ciclosporin
- Warm soaks, topical washes
- Antibiotics not needed unless secondary infection present
Canine juvenile sterile granulomatous dermatitis and lymphadenitis prognosis
- Good if treat early but may scar if treatment delayed -> may need to treat before histopath results return!
Feline SCC
- Common
- Affects older cats, usually unpigmented nasal planum, pinna, eyelids, esp white cats
- UV-related – possible link also with papilloma virus infection?
NB may be preceded by actinic (solar) keratosis
- erythematous plaque with erosion/ulceration/crust
- can transform to invasive SCC
Feline SCC clinical signs
- Usually flat, firm, ulcerated lesions -> tissue destruction
- Often crusted, often >1 lesion
Feline SCC diagnosis
- Biopsy -> histopathology
- Locally invasive but low metastatic potential
- NB still check chest radiographs/ FNA of drainage LNs before extensive therapy
Feline SCC tx
- depends on site and size of neoplasm
- Superficial tumours respond well to all therapies
- Infiltrative tumours need aggressive surgery + radiotherapy or adjuvant chemotherapy
Treatment options:
- Surgery: including pinnectomy, nasal planectomy
- Laser therapy or cryotherapy (early, shallow lesions)
- Imiquimod cream (human cytotoxic product) (early, shallow lesions)
- Photodynamic therapy
- Hyperthermia
- Radiotherapy
- Electrosurgery
Feline SCC - prevention of new lesions
- Sunblock
- Keep indoors in strong sunlight
- UV light blocking film on windows?
Canine SCC
- Less common than in cat
- Prognosis depends on site:
– Nasal planum, legs, scrotum, trunk
– Low metastatic potential
-> surgery (NB cosmetic considerations) - Claw bed (subungual) – common!
– More aggressive (majority dead within 1y of dx)
– often get missed as look like infected nail bed
Feline acne
- Dark waxy scales/crust on chin
- May be primary disorder, but often secondary (e.g. to dermatophytosis, demodicosis)
Often develop secondary Malassezia, pyoderma and furunculosis - Rule out demodicosis/dermatophytosis
- Address any secondary microbial infection
- Often maintenance management with topical keratolytic products
Calcinosis cutis
= inappropriate deposition of calcium phosphate in skin/subcutis
-> gritty white deposits -> provoke surrounding inflammation and crust
Usually due to
- Dystrophic calcification
– i.e. deposition in injured, degenerating or dead tissue
– e.g. HAC!!
Occasionally:
- Metastatic calcification (i.e. altered serum levels of calcium/phosphorus, e.g. chronic renal disease)
- Idiopathic (e.g. calcinosis circumscripta)
Superficial necrolytic dermatitis (SND)
= Hepatocutaneous syndrome
- affects middle-aged/older dogs
- lesions due to keratinocyte death associated with: end-stage liver disease,
pancreatic atrophy/ glucagonomas -> diabetes mellitus
SND clinical signs
- Hyperkeratosis of footpads (most cases)
- Erythema, ulcers/erosions, crusting, especially mucocutaneous areas, muzzle
distal limbs, hocks, elbows - +/- secondary infection
- +/- pruritus
SND diagnosis
- Histopathology, supported by relevant changes on haematology/biochemistry
- Imaging of abdomen, +/- liver biopsy
SND tx
- Dietary supplementation: amino-acids, EFAs, zinc, Vit E
- Treat secondary infections
- Address underlying cause if possible
SND prognosis
- often poor
Idiopathic facial dermatitis of Persians
- Poorly-understood condition
- Guarded prognosis
Idiopathic facial dermatitis of Persians clinical signs
Persian cats
– Tightly adherent, greasy black scales
–Malassezia dermatitis
Idiopathic facial dermatitis of Persians tx
- Anti-yeast therapy
- Ciclosporin ± prednisolone
