Crusting disease

• What is a crust?

  Dried exudate, containing blood/serum/scales/pus.

  Occasionally a primary lesion.

  Usually a secondary lesion:

  • Scaling
  • Pustular
  • Ulcerative.

  Crusting is very common but is usually not diagnostically helpful
• What are the first steps after noticing a crush?

  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 the crust (lift the crust up).
  • Dermatophytosis (especially cats) - Wood’s lamp, Dermatophyte culture.
• What is the most common thing to cause crusting?

  Superficial pyoderma.
• What is Canine pemphigus foliaceus

  Most common autoimmune skin disease in the dog.

  Middle aged to older dogs (but can occur at any age).

  Strong breed predisposition - Akita, Chows, Cocker spaniels, Dachshunds, Labradors, English Bulldogs & Shetland sheep dog.
• What are the clinical signs of Canine pemphigus foliaceus?

  Usually present as bilaterally symmetrical crusting disease.

  Lesions can occur anywhere, but head/pinnae involved in 80% of cases (which are unusually sited for a pyoderma).

  +/- pruritus

  +/- mildly unwell pyrexic.

  Secondary pyoderma is common and confusing -> there will be a partial response to treatment of pyoderma.
• What is the treatment for Canine pemphigus foliaceus?

  Induction:

  • Immunosuppresive doses of systemic GCC, usually Prednisolone rapid action.
  • +/- topical GCC
  • Treat until most of the lesions are healed and there are no new lesions for 10 days.

  Titration:

  • Taper slowly to the lowest effective maintenance dose, every other day if possible when using prednisolone.

  Can use an adjunctive immunosuppressive agent - to help minimise the steroid dose e.g. chlorambucil, Ciclosporin, Azathioprine.
• What is the prognosis for Canine pemphigus foliaceus?

  Often poor due to the adverse effects of treatments, steroids make the dog wee everywhere, eating everything, with adjunctive treatments need more monitoring which can become very expensive.
• What is feline pemphigus foliaceus?

  Less common than canine.

  Wide range of onset.

  Have to distinguish from an allergic cat with head, neck and face pruritus (lesion on the nose is unusual for an allergic cat but does present in PF).
• What are the clinical signs of feline pemphigus foliaceus?

  Same as the dog with crusting on pinnae, pedal lesions, bilaterally symmetrical facial pinnae distribution.

  Also the claw folds can be affected and so can the skin around the nipples (areolar skin), just less commonly.

  
• What is the diagnosis and treatment for feline pemphigus foliaceus?

  As for the dog except:

  • Occasionally oral dexamethasone (off-label) in place of prednisolone, have to be more careful as is more potent than prednisolone and is more diabetic.
  • +/- adjunctive treatments:
  • Chlorambucil (NB NOT Azathioprone for cats)
  • Ciclosporin, topical steroids.
  • Monitor fuctosamine when on steroids as the can develop diabetes.
• What is the prognosis for feline pemphigus foliaceus?

  Prognosis is better than the dog, as they are easier to manage than the dog.
• How does canine juvenile sterile granulomatous dermatitis and lymphadentitis present?

  Sterile granulomatous condition affecting the face, pinnae, ears and submandibular lymph nodes.

  Aetiology unknown - immune dysfunction

  Breeds - especially golden retreivers/labradors, Daxis.

  Age - usually puppies, occasionally adults.
• What are the clinical signs of canine juvenile sterile granulomatous dermatitis and lymphadentitis?

  Sterile pustules -> ulcers/draining tracts/crusts/hair loss and cellulitis affecting above areas.

  Acute swelling of the muzzle, lips, eyelids.

  Marked submandibular lymphadenopathy (if you have an allergic reaction will not have a lymphadenopathy).

  Rarely nodules at other sites

  +/- otitis externa

  +/- pyrexia, depression, anorexia, joint pain.
• How do you diagnose canine juvenile sterile granulomatous dermatitis and lymphadentitis?


  Based off of signalment, history and clinical signs, but it is important to rule out other diseases that can cause cellulitis:

  • Demodicosis
  • Infections - bacterial pyoderma, dermatophytosis.

  Biopsy confirmatory - send for histopathology and tissue culture.
• What is the treatment for canine juvenile sterile granulomatous dermatitis and lymphadentitis?


  Prednisolone (immunosuppressive doses) to resolution (7-14 days), then taper slowly to withdraw.

  +/- other immunosuppressive agents e.g. Ciclosporin.

  Warm soaks, topical washes to help with the crusting.

  Antibiotics are not needed unless secondary infection present.
• What is the prognosis for canine juvenile sterile granulomatous dermatitis and lymphadentitis?


  Good if treat early, but may scar if treatment delayed -> may need to treat before histopath results return.

  Demodex autolyses so have to diagnose it yourself as it will have disappeared by the time an external lab looks at it.
• How feline squamous cell carcinoma present?

  Affects older cats, especially white cats.

  Usually presents as unpigmented nasal planum, pinna, eyelids.

  UV related - possible link also with papilloma virus infection.

  May be preceded by actinic (solar) keratosis - erythematous plaque with erosion/ulceration/crust, can be there for a long time, but will progress to a much more invasive thing (invasive SCC).

  
• What are the clinical signs of feline squamous cell carcinoma?

  Usually flat, firm, ulcerated lesions -> tissue destruction, start to erode.

  Often crusted. Often >1 lesion.
• How do you diagnose feline squamous cell carcinoma?

  Biopsy - histopathology.

  Locally invasive but low metastatic potential.
• What is the treatment and prevention for feline squamous cell carcinoma?

  Treatment depends on site and size of neoplasm:

  • Superficial tumours respond well to all therapies.
  • Infiltrative tumours need aggressive surgery + radiotherapy or adjuvant chemotherapy.

  Prevention of new lesions:

  • Sunblock (white cats)
  • Keep indoors in strong sunlight
  • UV light blocking film on windows.
• What are the treatment options for feline squamous cell carcinoma?

  Surgery - including pinnectomy, nasal planectomy.

  Laser therapy or cryotherapy (early, shallow lesions)

  Imiquimod cream (early, shallow lesions).

  Photodynamic therapy

  Hyperthermia

  Radiotherapy

  Electrosurgery.
• What is the prognosis for canine squamous cell carcinoma?

  Depends on site:

  Nasal planum, legs, scrotum, trunk:

  • Low metastatic potential
  • -> surgery (note cosmetic considerations).

  Claw bed (subungual) - common

  • Get missed as they look like a nail bed infection.
  • More aggressive (majority are dead within a year of diagnosis).
• Feline acne

  Dark waxy scales/crust on chin.

  Can be a primary keratinisation.

  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 with topical keratolytic products.
• How does superficial necrolytic dermatitis present?

  Mild depression, weight loss.

  Mild lameness

  Hyperkeratosis of footpads (feet are very commonly affected).

  Skin disease is a sign of something systemically wrong.

  Lesions can be associated with end-stage liver disease or pancreatic atrophy/glucogonomas -> diabetes mellitus
• What are the clinical signs of superficial necrolytic dermatitis?

  Hyperkeratosis of footpads

  Erythema, ulcers/erosions, crusting especially:

  • Mucocutaneous areas, muzzle
  • Distal limbs, hocks, elbows.

  +/- secondary infection.

  +/- pruritus.
• How do you diagnose superficial necrolytic dermatitis?

  Histopathology supported by relevant changes in haematology/biochemistry.

  Imaging of the abdomen +/- liver biopsy.
• What is the treatment for superficial necrolytic dermatitis?

  Not very effective for very long.

  Dietary supplementation - amino-acids, EFAs, zinc, Vit E

  Treat secondary infections.

  Address underlying cause if possible.

  Prognosis is often poor.
• Idiopathic facial dermatitis of Persians

  Poor understood condition.

  Persian cats:

  • Tightly adherent, greasy black scales.
  • Malassezia dermatitis.

  Treatment:

  • Anti-yeast therapy
  • Ciclosporin +/- prednisolone

  Guarded prognosis.
• A 6yo DLH cat presents with bilaterally symmetrical crusting affecting the pinnae and face, and a caseous law fold exudate affecting multiple digits. What is your top differential diagnosis?

  Pemphigus foliaceus