23.11.3: Scale disease Flashcards
For more detail on treatments, see specific lecture notes ('Scale disease - 1/3/2023'). Details of different moisturisers not included here.
What is scale and what does it result from?
Scale: presence of flakes of keratin in the hair coat and on the skin. Scale may be adherent (well attached to the epidermis) or loosely attached.
Scale results from:
* Normal skin function (a little scale a.k.a. dandruff = normal in many situations)
* Abnormal desquamation (shedding of corneocytes)
* Abnormal cornification (creation of the outer epidermal layers)
* Inflammation (inflammation induces cell turnover)
* Bacterial and fungal enzymatic action
Diseases in which scale is noted
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Diseases in which scale is noted
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Which is more common: primary or secondary scale?
Secondary scale is very much more common than primary disease.
Diagnostic plan for animal presented with scaling disease
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Signalment and presentation of Zinc-responsive dermatosis
Signalment
* Genetically predisposed breeds e.g. Huskies have Type I = genetic poor absorption of zinc
* Often young adult onset in winter
* Type II = nutritional restriction in young, rapidly growing large breeds
* Beware concurrent hypothyroidism (older animals, later onset)
Clinical presentation
* Dull coat and specific hard plaques with marked scale and crusting; lesions occur wherever dog knocks itself
* Crusted hyperkeratosis (bacterial infection common) -> lift crust and do cytology to check for infection
* ± Bacterial infection
* Variable pruritus, more so if infected
Zinc responsive dermatosis
Histological findings with zinc-responsive dermatosis
- Parakeratosis is a key finding
- Nuclei are retained in the stratum corneum; this is seen to a lesser extent in bacterial pyoderma and in superficial necrolytic dermatitis
- Zinc is required for normal keratinisation -> disease most common at areas of trauma
Treatment of zinc-responsive dermatosis
- Zinc supplementation - Zinc sulphate traditionally used but may cause vomiting
- Correct diet
- Consider steroids if Type I and poor response (hard to get enough zinc into a husky, a tiny amount of anti-inflammatory dose steroids help but we don’t know how)
History and clinical presentation of ichthyosis of Goldern Retrievers
- Seen from a few weeks old; scale variable over life but can be severe; need to rule out ectoparasites as a ddx
- Barrier function is not compromised -> secondary infection is uncommon, secondary otitis can occur
- Genetic disease, recessive allele -> genetic testing recommended
Treatment of ichthyosis of Golden Retrievers
- Symptomatic treatment only
- Manage with shampoos
- Vitamin A-like analogues (retinoids) used with some success but quite severe drugs
Signalment and clinical presentation of canine ear margin seborrhea
- Relatively uncommon
- Marked breed predilection in Dachshunds
- Can be a feature of hypothyroidism
- Adherent keratin on both medial and lateral sides of the pinna
- Follicular casts and plugs may trap hair
- Rubbing produces erosions and ulceration
- Pruritus is variable
- Fissuring and secondary infection can be problematic
Differential diagnoses for canine ear margin seborrhea
- Secondary causes of pinnal seborrhea
- Hypothyroidism
- Trauma due to pinnal flapping
- Early vasculitis
- Early localised scabies
Diagnosis and treatment of canine ear margin seborrhea
Important differential diagnoses for nasodigital hyperkeratosis
There are many possible ddx. Important ones:
* Superficial necrolytic dermatitis - would expect animal to be painful, systemically unwell, and more widespread disease
* Epitheliotropic cutaneous lymphoma - hypopigmentation, ulceration, progression beyond the nose and pads
* Demodicosis (foot pad disease) - rare, look for signs of mites elsewhere on the dog
Signalment of nasodigital hyperkeratosis
Nasodigital hyperkeratosis: broad term for dogs with non-iflamed, quiescent and tightly adherent hyperkeratosis affecting the nose and sometimes the feet.
* Usually older dogs
* No sex or breed predisposition
* Probably a senile change
Clinical signs of nasodigital hyperkeratosis
- Nasal lesions can be variable: frond-like projections or hard surface. Nose is dry, and cracks and fissures can occur and lead to irritation.
- Pad lesions: all pads affected, and most prominent at edges due to weight bearing. Lack of flexibility of pad leads to cracking, formation of corns, lameness.
Nasodigital hyperkeratosis
Diagnosis of nasodigital hyperkeratosis
Treatment of nasodigital hyperkeratosis
- Cut off prominent fronds with scissors or scalpel blade
- Hydrate the keratin using shampoos and soaks
- Essential fatty acids PO
Nasal parakeratosis of Labrador Retrievers
History and clinical signs of Nasal parakeratosis of Labrador Retrievers
Differential diagnoses, diagnosis and treatment of nasal parakeratosis of Labrador Retrievers
History and clinical signs of footpad hyperkeratosis of Dogue de Bordeaux
There is popilteal and prescapular LN enlargement in cases of pedal infection (where the skin has split and enabled bacterial infection)
Footpad hyperkeratosis of Dogue de Bordeaux
Diagnosis and treatment of footpad hyperkeratosis of Dogue de Bordeaux
Where are calluses typically formed? If they are found elsewhere, what might this tell you about your patient?
- Often found over hocks, elbows, sternum, ischium
- Callus = normal response to pressure-induced ischaemia and inflammation
- Secondary infection is common
- Other areas involved - may suggest orthopaedic problems or hypothyroidism
Diagnosis and treatment of calluses
Diagnosis
* Typical clinical signs and position
* Can perform skin surface and exudate cytology -> bacterial cylture
* Can perform biopsy if needed for tissue culture
Treatment
* Treat secondary infection
* Remove trauma / pressure
* Consider bandaging and padding
* Surgery can help but need to consider if post-surgery the same factors that caused the callus will remain and lead to breakdown of the wound
Signalment and clinical signs of thymoma-induced exfoliative dermatitis
This is a cutaneous marker of systemic disease.
Diagnosis and treatment of thymoma induced exfoliative dermatitis
You think you have diagnosed a dog with idiopathic canine sebaceous adenitis, but then you suddenly realise it has previously travelled abroad. What do you now need to consider?
Histological sebaceous adenitis can be seen in a variety of disease but particularly Leishmaniasis
Pathogenesis of idiopathic sebaceous adenitis
Clinical signs and diagnosis of idiopathic sebaceous adenitis
Idiopathic canine sebaceous adenitis
Treatment of idiopathic canine sebaceous adenitis
2 major categories of treatment for scaling disease
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