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Y4 SA dermatology > Crusting disease > Flashcards

Crusting disease Flashcards

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Dermatology Board Prep flashcards
1
Q

What is a crust?

A

= 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

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2
Q

What is the most common cause of crusts in dog?

A
  • superficial pyoderma
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3
Q

What to do when see a crust?

A
  • 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
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4
Q

Diseases presenting primarily as crusting

A
  • 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
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5
Q

Canine pemphigus foliaceous

A
  • 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)
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6
Q

Pathogenesis of canine pemphigus foliaceous

A
  • 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
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7
Q

Cytology of pemphigus foliaceous

A
  • Acantholytic keratinocytes (large ‘fried-egg’ cells, sometimes in rafts) + neutrophils
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8
Q

How are the pustules in pemphigus foliaceous different to pustules in pyoderma?

A
  • 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

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9
Q

Canine pemphigus foliaceous clinical signs

A
  • 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!
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10
Q

Canine pemphigus foliaceous tx

A
  • 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
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11
Q

Canine pemphigus foliaceous prognosis

A
  • Often poor due to adverse effects of treatments
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12
Q

Feline pemphigus foliaceous

A
  • 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”
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13
Q

Feline pemphigus foliaceous diagnosis, tx + prognosis

A
  • 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
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14
Q

Canine juvenile sterile granulomatous dermatitis and lymphadenitis

A
  • 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
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15
Q

Canine juvenile sterile granulomatous dermatitis and lymphadenitis clinical signs

A
  • 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
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16
Q

Canine juvenile sterile granulomatous dermatitis and lymphadenitis diagnosis

A
  • 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
17
Q

Canine juvenile sterile granulomatous dermatitis and lymphadenitis tx

A
  • 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
18
Q

Canine juvenile sterile granulomatous dermatitis and lymphadenitis prognosis

A
  • Good if treat early but may scar if treatment delayed -> may need to treat before histopath results return!
19
Q

Feline SCC

A
  • 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

20
Q

Feline SCC clinical signs

A
  • Usually flat, firm, ulcerated lesions -> tissue destruction
  • Often crusted, often >1 lesion
21
Q

Feline SCC diagnosis

A
  • Biopsy -> histopathology
  • Locally invasive but low metastatic potential
  • NB still check chest radiographs/ FNA of drainage LNs before extensive therapy
22
Q

Feline SCC tx

A
  • 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
23
Q

Feline SCC - prevention of new lesions

A
  • Sunblock
  • Keep indoors in strong sunlight
  • UV light blocking film on windows?
24
Q

Canine SCC

A
  • 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
25
Q

Feline acne

A
  • 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
26
Q

Calcinosis cutis

A

= 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)

27
Q

Superficial necrolytic dermatitis (SND)

A

= Hepatocutaneous syndrome
- affects middle-aged/older dogs
- lesions due to keratinocyte death associated with: end-stage liver disease,
pancreatic atrophy/ glucagonomas -> diabetes mellitus

28
Q

SND clinical signs

A
  • Hyperkeratosis of footpads (most cases)
  • Erythema, ulcers/erosions, crusting, especially mucocutaneous areas, muzzle
    distal limbs, hocks, elbows
  • +/- secondary infection
  • +/- pruritus
29
Q

SND diagnosis

A
  • Histopathology, supported by relevant changes on haematology/biochemistry
  • Imaging of abdomen, +/- liver biopsy
29
Q

SND tx

A
  • Dietary supplementation: amino-acids, EFAs, zinc, Vit E
  • Treat secondary infections
  • Address underlying cause if possible
30
Q

SND prognosis

A
  • often poor
31
Q

Idiopathic facial dermatitis of Persians

A
  • Poorly-understood condition
  • Guarded prognosis
32
Q

Idiopathic facial dermatitis of Persians clinical signs

A

Persian cats
– Tightly adherent, greasy black scales
–Malassezia dermatitis

33
Q

Idiopathic facial dermatitis of Persians tx

A
  • Anti-yeast therapy
  • Ciclosporin ± prednisolone

Y4 SA dermatology (22 decks)

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