Scale Flashcards
What is scale?
- the presence of flakes of keratinized skin in the hair coat and on the skin
- it can be adherent (well attached to the epidermis) or loosely attached
- thickened stratum corner
What does scale result from?
▪Normal skin function ( a little scale (dandruff) is normal in many situations)
▪Abnormal desquamation (shedding of corneocytes)
▪Abnormal cornification (creation of the outer epidermal layers)
▪Inflammation (inflammation influences cell turnover and structures)
▪Bacterial and fungal enzymatic action
Are scale and crust the same thing?
- no
- crusts result from the hardening of pus, serum and/or blood with scale to form a solid material which like scale is variably adherent to the skin
Diseases where scale is seen as a primary problem
▪ Primary keratinization disorders
– Particularly ichthyosis
– Several breeds
▪ Primary seborrhoea
– A poorly defined group of conditions with scale and sometimes greasiness
▪ Zinc–responsive dermatosis
▪ Ichthyosis of the golden retriever
▪ Ear margin seborrhoea
▪ Nasodigital hyperkeratosis
Diseases where scale is seen as a secondary problem
▪ Callus (compact adherent scale)
▪ Hypothyroidism
▪ Allergy
▪ Parasites
▪ Bacterial infection
▪ Dermatophytosis
▪ Sebaceous adenitis
▪ Almost any resolving inflammatory dermatosis
▪ Exfoliative dermatitis in cats (2 ̊ to thymoma)
▪ Leishmaniasis
Is primary or secondary scale more common?
- secondary scale is much more common that primary dz
Is scale in bacterial infections common?
- yes
- it is 1 of the most common forms of scale seen in dogs (may be the O main concern/presenting complaint)
- Staphylococcus pseudintermedius causes folliculitis and following rupture of the pustule and central hair loss a spreading circle of scale is seen moving from the central area
- The amount of scale depends on bacterial toxins (esp. exfoliative toxins)
Diagnostic plan
- Check for parasites
- Check for infection
- In older dogs perform general health screening (e.g. urinalysis, haematology & biochem)
- Biopsy
- Genetic testing if indicated
Checking for parasites
a. Clinical examination
b. Coat brushings, hair plucks, skin scrapes
c. Consider parasite treatment trial
Particularly important in young animals, don’t rely on reported ectoparasite use
Checking for infection
a. Clinical examination
b. Skin surface cytology
If infection, what is the primary dz?
Genetic testing
a. Ichthyosis of the Golden retriever†, Great Dane and American Bulldog
b. Pedal hyperkeratosis of the Dogue de Bordeaux
c. Nasal parakeratosis of Labrador Retrievers (NPLR) †
† Common in the UK
Zn-responsive dermatosis - which animals are affected?
▪Genetically predisposed breeds eg Husky (type I)
– Often young adult onset
▪In nutritional restriction seen in young rapidly growing large breeds (type II)
Zn-responsive dermatosis - what is type I?
▪Genetic poor Zn absorption
Zn-responsive dermatosis - what concurrent dz do you need to be aware of with type I?
- hypothyroidism (older animals - later onset)
Zn-responsive dermatosis - CS
▪Dull coat and specific hard plaques with marked scale and crusting
▪Crusted hyperkeratosis (bacterial infection common)
▪Bacterial infection
▪Variable pruritus
– due to infection
▪Crusted lesions where they bash their skin
Zn-responsive dermatosis - histologically (from biopsy)
▪Parakeratosis is key finding
▪Zinc is required for normal keratinisation – disease most common at areas of trauma
▪In parakeratotic hyperkeratosis nuclei are retained in the stratum corneum
– This is seen to a lesser extent in bacterial pyoderma and in superficial necrolytic dermatitis (hepatocutaneous syndrome)
– Normal squares should not have nuclei
Zn-responsive dermatosis - tx
- Zn supplementation, correct diet (consider steroids in type 1 if poor response)
– steroid in v low doses can increase the absorption of zinc - Zinc sulphate traditionally used
– may cause v+
Ichthyosis of the Golden Retriever - History & CS
▪Seen from a few weeks of age, scale is variable over life, but can be severe
▪Barrier function is not compromised so 2 ̊infection is uncommon, but can get 2 ̊otitis
▪ Fine in themselves, just v scaly
▪ Can get wax ears as exfoliates out of the skin/ear less well
▪ Scale easily brushed off
▪ Can see shiny adherent material on ears and ventral abdomen
▪ Ichthyosis = fish scale dz
Ichthyosis of the Golden Retriever - tx
▪Symptomatic treatment only
▪Recently retinoids used with some success
Ichthyosis of the Golden Retriever - what is it?
A genetic disease
▪An insertion-deletion mutation in exon 8 of PNPLA1-gene (patatin-like phospholipase domain-containing protein 1) was identified that leads to a premature stop codon
▪Abnormal cleavage of the corneodesmosome
Ichthyosis of the Golden Retriever - Major ddx in young animals
- parasites
– if several in litter affected, consider skipping biopsy and performing genetic test after ruling out mites
Is canine ear margin seborrhoea common?
- no it is relatively uncommon
Canine ear margin seborrhoea - breed predilection
- Marked breed predilection in Dachshunds
Canine ear margin seborrhoea - CS
▪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
▪ Very sore
Canine ear margin seborrhoea - ddx
▪Secondary causes of pinnal seborrhoea
▪ hypothyroidism
▪Trauma due to pinnal flapping
▪Early vasculitis
– But not vasculitis as no notches/necrotic tissue due to lack of blood supply
▪Early localised scabies
Canine ear margin seborrhoea - diagnosis
▪When restricted to the ear margins alone in the Dachshund: diagnosis on clinical signs
▪Rule out other causes
– particularly early sarcoptic
mange and other ectoparasites
▪Biopsy
– Use edge resection rather than wedge for best cosmetic effect (but may not get many sebaceous glands) and to avoid vascular compromise
-> Notch ends up with compromised blood supply -> more problems that before
– Retract skin before resection to ensure adequate closure
– Bilateral so O doesn’t really notice once hair grows back
– Resection can also be sent away for histopath if concerned
Canine ear margin seborrhoea - tx
▪incurable condition
▪topical anti-seborrhoeic shampoos, combined with moisturisers.
▪Fissures should be treated with surgery if steroids (e.g. hydrocortisone aceponate) are not useful.
Nasodigital hyperkeratosis - what is it?
▪A broad term for dogs with non- inflamed, quiescent and tightly adherent hyperkeratosis affecting the nose and sometimes the feet
Nasodigital hyperkeratosis - history
▪Long list of differential diagnoses, but most affect other areas
▪Usually older dogs
▪No sex or breed predisposition ▪Probably a senile change
▪Associated with Distemper virus
Nasodigital hyperkeratosis - nasal lesions
▪frond-like projections to a hard
pavement-like surface
▪the nose is dry
▪cracks and fissures can occur leading to irritation
Nasodigital hyperkeratosis - pad lesions
▪all the pads
▪most prominent at the edges - weight bearing
▪lack of flexibility, cracking and the formation of corns lead to lameness
Nasodigital hyperkeratosis - ddx
▪Superficial necrolytic dermatitis
– Painful, systemically unwell
– Often 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 dog
Nasodigital hyperkeratosis - diagnosis
▪ Clinical signs in the older dog with
no other skin problems
– Slowly developing
– Bilaterally symmetrical
▪Not appropriate if
– Generalised or systemic disease
– Ulceration
– Depigmentation
– Pain on localised palpation
▪If in doubt biopsy
– Difficult – ensure stitches in living epithelium
Nasodigital hyperkeratosis - tx
▪ cutting off prominent fronds with
scissors or a scalpel blade
▪ hydrating the keratin using shampoos and soaks as described elsewhere
▪ Essential fatty acids
Nasal parakeratosis of Labrador Retrievers - history
▪First observed between 6 & 12 months
▪ Affects all colours
▪ Often several members of the family affected
Nasal parakeratosis of Labrador Retrievers - CS
▪ Roughening of the nasal skin
▪ Moderate hyperkeratosis
▪ Some (often diffuse) hypopigmentation
▪ Clear demarcation on bridge of the nose (sometimes affected by previous topical agents)
Nasal parakeratosis of Labrador Retrievers - ddx
▪ Discoid lupus erythematosus and mucocutaneous pyoderma
How to tell the difference between nasal parakeratosis and pemphigus or lupus
- pemphigus/lupus: wouldn’t expect the clarity between the nose and face
- discoid lupus: ulceration and pigmentation
- nasal parakeratosis: nothing on lips or down towards mouth
Nasal parakeratosis of Labrador Retrievers - diagnosis
▪ Biopsy
▪Genetic testing
Nasal parakeratosis of Labrador Retrievers - tx
▪Treatment is for life and affected dogs should not be bred from
▪ Zinc supplementation, steroids and retinoids give a poor response
▪ Topical vitamin E, petroleum jelly and propylene glycol have been advocated.
▪ Urea based humectants and petroleum jelly chronically after good antimicrobial treatment useful
Footpad hyperkeratosis of the Dogue de Bordeaux - History
▪ Present in the UK
▪First signs start at 4-6 months of age
▪ Larger animals (males) appear to start signs earlier suggesting a mechanical component to the disease
Footpad hyperkeratosis of the Dogue de Bordeaux - CS
▪Foot pads only, with severe thickening with deep cracks appearing centrally
▪conical to flap like projections appearing at the edges of the pads
▪ Lameness on rough ground
– Very painful
▪ Often signs of bacterial infection (cytological or pedal swelling and peripheral lymph node enlargement)
Footpad hyperkeratosis of the Dogue de Bordeaux - diagnosis
▪history and clinical signs
▪biopsy
– a deep wedge from the middle of the pad and crossing the hyperkeratotic edge
– close using deep and widely placed vertical mattress sutures to hold the opposing sides of the pad in position so that simple interrupted sutures along the incision are not pulled.
▪Genetic testing (keratin 16 abnormality)
Footpad hyperkeratosis of the Dogue de Bordeaux - tx
▪50% propylene glycol soaks (requires an obedient dog and willing owner)
– Problems occur when dog aggressive
▪Retinoids – very expensive in 60-80 kg dog
– Also associated with a worry about psychotic episodes in people
– Difficult to get hold of
▪Antibiotics for secondary infection ▪Affected dogs should not be bred
What is a callus?
▪ Callus is the normal response to pressure induced ischemia and inflammation
▪ Reactive epidermis that results in scale build up on top
Callus - history & CS
▪round or oval hyperkeratotic plaque that develops on the skin at points of trauma.
▪Often hocks, elbows, sternum and ischium
▪Other areas involved when orthopaedic problems or hypothyroidism
▪Secondary infection is common.
Callus - diagnosis
▪typical clinical signs and
position, combined
▪Biopsy* especially if needed for tissue culture
▪Skin surface and exudate cytology and bacterial culture should be employed
- Care with biopsy
– Small punch biopsy to not lose integrity of the area
– Histology ± tissue culture
Callus - histopathology
▪epidermal hyperplasia
▪moderate to severe acanthosis
▪variable epidermal hyperkeratosis sometimes parakeratotic.
▪Follicles are often cystic with keratin and hair fragments leading to furunculosis)
Callus - tx
▪treatment of the secondary infection
– Deep pyoderma is a common complication
– Extended therapy makes Meticillin-resistant & MRD bacteria likely ▪removal of the trauma / pressure
▪Bandaging and padding?
▪Surgery is possible
– often curative for sternal lesions
– limb lesions often breakdown post surgery as the factors that led to the
callus cannot be removed
– Even risk for extensive biopsy
– Limbs ones refer
When do you know you need to treat a callus?
- Pick it up and roll it
- Deep pyoderma = ricey grainy bits
Thymoma induced exfoliative dermatitis - signalment
▪Rare paraneoplastic syndrome ▪Middle to older age
Thymoma induced exfoliative dermatitis - CS
▪Diffuse, non-pruritic erythema and exfoliation (large 1+ cm flakes if skin) +/- alopecia
– Can peel the scale away, brings the hair with it
▪Concurrent signs from respiratory compromise
– High resp rate due to chest mass
Thymoma induced exfoliative dermatitis - diagnosis
▪ Biopsy
▪Chest radiography / CT
– Cranial thoracic mass on imaging
Thymoma induced exfoliative dermatitis - tx
▪Immunomodulatory drugs (e.g. prednisolone & ciclosporin) have been used with some success
▪Surgery is reported to be curative, but some have reported needing immunosuppression after thymoma removal
What is exfoliative dermatitis reported in?
- rare cases of FASS
Idiopathic canine sebaceous adenitis - background
▪Inflammation in the sebaceous glands resulting in reduced activity to
complete loss
▪Not uncommon
▪Autosomal recessive mode of inheritance in poodles and Akitas ▪Considered by some to be brought about by a stressful event
▪ Vislas commonly affected, and present with segmental alopecia and scale
What dz might you see histological sebaceous adenitis?
- a variety of diseases
- particularly Leishmaniasis
Idiopathic canine sebaceous adenitis - CS
▪Dry scale: Fine, white and non-adherent
▪Hair loss (variable): Hair breakage and matting together and secondary infection
▪Perifollicular hyperkeratosis is prominent
▪Follicular casts are common
▪Pruritus when 2 ̊ infection present
Diffuse partial alopecia with lots of scale, if pluck hairs see follicular casts
Symmetrical
Alopecia and scale can be segmental
Idiopathic canine sebaceous adenitis - diagnosis
▪Clinical signs highly suggestive
▪Rule out possible differential diagnoses and confounding co-morbidities
▪Biopsy: Absent sebaceous glands gives a clear diagnosis
Idiopathic canine sebaceous adenitis - tx
▪Use emollient and lubricating shampoos
– Improve cosmetic appearance
– Consider the ‘cling film wrap’
▪Fatty acid and oil supplementation
– Topically
– Systemically
▪ Ciclosporin
– Drug of choice
– Direct action on T-cell destruction and
may also promote hair cycling (initiates anagen)
▪Steroids may be used, but reduction in hair cycling not useful
Idiopathic canine sebaceous adenitis - prognosis
▪Good if seen early
▪Some cases do well for many years and then develop alopecia in old age despite treatment – unknown mechanism
Non-specific treatment – topicals
- Keratoplastic / keratolytic products
- Moisturising and emollient products
Most cases need both types of products
Keratoplastic/keratolytic products - what do they do? When to use them
▪These reduce scale production (keratoplastic [e.g. sulphur and coal tar shampoos]) or remove scale (e.g. salicylic acid shampoos])
▪Delicate balance between removing scale and causing excessive drying
▪Used before moisturising products
Moisturising and emollient products - what do they do? When to use them
▪These reduce transepidermal water loss and prevent inflammation (e.g. products containing oils, propylene glycol and urea).
▪Best used after other products have removed scale (e.g. keratolytic shampoo) and/or shampoo has been used to treat secondary skin surface infection
Forms of topical treatments & their action
▪Shampoos
– used with water & rinsed
– some have residual action
▪Foams
– residual action
▪Sprays
– residual action (lipophilic agents bind to lipid = reservoir)
▪Wipes
– physical interaction and residual action in some
▪Creams
– local treatment (water based)
– easily absorbed
▪Gels
– local treatments (often contain mixture of components to aid absorption)
▪Ointments
– local treatment (oil based) occlusive and remain in place
▪Spot-on products
– provide drugs for surface or systemic absorption
Keratoplastic vs keratolytic
Keratoplastic = reducing cell turnover in the skin to reduce scale production
- e. g. sulphur & tar
Keratolytic = in which the shampoo removes cells from the surface of the skin
- e. g. salicylic acid
What do emollient agents do? Types
- They moisturise and restore barrier function
▪Occlusive (greasy agents e.g. lanolin) ▪Hydrophilic (molecules that bind/trap water
e.g. urea or propylene glycol) - Can be combined
Important topical agents for scaling conditions
▪Sulphur
▪Salicylic acid
▪Selenium sulphide
▪Hydrocortisone aceponate
▪Betamethasone (and other
steroids in ear creams)
Sulphur - properties & use
▪ Keratoplastic
– Cytostatic on basal cell layer of epidermis so slows down epidermal cell proliferation
▪Keratolytic
– Forms hydrogen sulphide / pentathionic acid that damage corneocytes softening stratum corneum causes shedding of cells
▪Antibacterial / antifungal
▪Not very degreasing so doesn’t dry out skin
▪ Used for mild grease, scale and proliferation
– e.g. primary seborrhoea (over productions of scale with marked reduction in skin turnover time)
▪ Combined with salicylic acid to increase degreasing power (synergistic activities)
▪ Recommended to use moisturiser if skin dry
Salicylic acid - properties & use
▪Often combined with sulphur as synergistic
▪Treatment of seborrheic conditions (1 ̊ and 2 ̊)
▪ Keratolytic
– Lowers pH of skin
– Hydrates keratin / causes swelling of corneocytes
– Stabilises inter-cellular cement in stratum corneum
-> desquamation
▪No effect on mitotic rate of basal keratinocytes
▪Mildly anti-pruritic
▪Mildly anti-inflammatory
▪Recommended to use moisturiser if skin dry
Typical use of sulphur-salicylic acid shampoo
- to remove scale
- reduction in skin barrier function increases natural water loss and causes inflammation
- a moisturiser is essential after scale removal
Selenium sulphide - properties & use
▪Older anti-seborrheic but can be used to treat severe cases of oily greasy skin non-responsive to other agents
▪Keratolytic
–Inteferes with hydrogen-bond formation in keratin
▪Keratoplastic
–Depresses epidermal growth
▪Antimicrobial
–Fungicidal at higher concentrations
▪Causes marked skin drying (irritation potential)
▪Stains coat (pink)
Irritant and old school, but very keratoplastic. Use in extreme need
Emollients and Moisturisers - properties & use & examples
▪Include fats / hydrocarbons / humectants / oils
▪Act as vehicles for other ingredients
▪Soften / protect skin
– Form a thin film of oil on stratum corneum
– Decrease water loss
– Occlusive function
▪Act to bind water in the skin
– Hydroscopic function
Examples:
* Zinc gluconate
* D-panthenol
* Liposomes
* Glycerin
* Propylene glycol
Common moisturisers
- Urea
- Glycerin
- Propylene glycol
- Vaseline
Urea - mechanism of action, notes re use
Binds water
* Promotes hydration
* Anti-bacterial
* Keratolytic
* Proteolytic digestion of fibrin
Used in shampoos such as Sebocalm in combination with glycerin
Glycerin - mechanism of action, notes re use
Hygroscopic / absorbed into skin
Used in shampoos and conditioning foams and sprays and wipes (e.g. with chlorhexidine in Clorexyderm range)
Propylene glycol - mechanism of action, notes re use
Potent softening and hydroscopic agent
Used neat or diluted 50% in water for severe pad hyperkeratosis
Common component of conditioning products
Vaseline - mechanism of action, notes re use
Petroleum jelly, is a safe occlusive agent
Can be greasy and mark clothes and soft furnishings
Other agent that improve barrier function
- topical essential fatty acids
- colloidal oatmeal
- lanolin
- phytosphingostine
Topical essential fatty acids - mechanism of action, notes re use
Attempt to restore lipid layers in stratum corneum
Expensive and controversial efficacy e.g. Allerderm Spot-on
Colloidal oatmeal - mechanism of action, notes re use
Hygroscopic and soothing
Reduced pro-inflammatory cytokines
aka anti-pruritic and anti-inflammatory
Used in shampoos e.g. Coatex Aloe and oatmeal shampoo
Lanolin - mechanism of action, notes re use
Occlusive agent
Common in creams and conditioners
Phytosphingosine - mechanism of action, notes re use
Natural product found in epidermis (SC) and in various plants and fungi Increases barrier function and may reduce pro-inflammatory cytokines
Anti-inflammatory and antipsoriatic activities of the phytosphingosine derivatives inhibited NF-κB, JAK/signal transducer and activator of transcription (JAK/STAT), and mitogen-activated protein kinase (MAPK) signaling
Now largely removed from the veterinary market for commercial reasons.
Systemic agents that may affect keratinisation (& how they work)
Steroids
▪Reduce the turnover of epithelial cells
▪May reduce scale in some cases
▪Local application useful (e.g. ear margin seborrhoea)
Retinoids
▪Normalise skin development, used in a variety of disorders of hyperkeratosis ▪High number of adverse effects e.g. dry eye, hepatopathy
▪A referral medication
Why does hypothyroidism result in scale?
- change in epidermal turnover
What do Dalmations or pale dogs get after pustules and scale?
- black pigmentation / post inflammatory macule
