Non-pruritic alopecia Flashcards
What is alopecia?
What are the different types?
- Loss of hair
- The absence of hair
Can be:
* Partial or complete
* Localised, generalised, symmetrical or multifocal
* A primary or secondary lesion!
- Spontaneous – hair falls out
- Self-induced – animal takes hair out
What is Hypotrichosis?
used synonymously by some for partial alopecia – preferred for poor growth of hair not partial loss e.g. Hair is growing sparsely
Why is signalment and age of onset important with alopecia history?
Breed predisposition and the Age of onset is important as there are Congenital alopecias that will aprear later in life
What do you need to think about when doing a physical exam for alopecia?
- Character AND distribution of lesion
- Character of alopecia
- Partial/complete
- Regular/irregular patches
- Sharp/gradual edge
- Distribution
- Asymmetrical vs symmetrical
- Focal/multifocal vs generalised
- Other skin lesions
- Erythema, hyperpigmentation, scaling, comedones, skin atrophy
Remember to re-evaluate as you examine, particularly when poor history whether alopecia is spontaneous or self-induced
What are the inflammatory causes of alopecia?
Infectious agents, parasites and immune mediated:
- Infectious agents
- Bacterial folliculitis (see infection)
- Dermatophytosis
- Parasitic
- Demodicosis
- Leishmaniasis (see scaling)
- Immune-mediated
- Alopecia areata
- Dermatomyositis
- Sebaceous adenitis
What are the non-inflammatory causes of alopecia?
Hair follicle arrest and hair synthesis defects:
- Hair follicle arrest
- Endocrinopathies
- Alopecia X
- Telogen defluxion
- Paraneoplastic alopecia
- Cyclical flank alopecia
- Post-clipping alopecia
- Injection alopecia
- Hair synthesis defects
- Congenital alopecias
- Pattern alopecia
- Follicular dysplasia
- CDA / BHFD
- Anagen defluxion/effluvium
- Sebaceous adenitis
What is the most common cause of infecticous causes of alopecia?
What does this look like?
How do you investigate it?
bacterial folliculitis:
* Most common cause in dogs and cats
* Staphylococcus pseudintermedius (and other commensal flora)
* Focal to multifocal patches of alopecia
* +/- pustules, crusts
* Especially short-coated dogs = ’short-coat pyoderma’
* Impression smear cytology
What species of dermatophytes affect cats and dogs most commonly?
What is the apperance of this?
Microsporum canis (zoophilic)
* zoonotic
Physical exam:
Often mild disease with scale and associated alopecia
* Multifocal patches often circular
* typical size 4-6 cm
* +/- hyperpigmentation
* Follicular casts
Mostly non-pruritic
Often the head, ears and chin
- In more severe cases multifocal alopecia becomes confluent and is complicated by secondary bacterial pyoderma
- Remember to do cytology even in proven cases
Only very rarely human ringworm (anthropophilic; reservoir people) causes disease in animal species.
What species of ring worm can often resemble deep pyoderma due to the fact they cause inflammation?
Trichophyton species
How is ringworm diagnosed?
Wood’s lamp examination
* Warm for 5-10 mins, expose hair for 3-5 mins
* Apple green fluorescence of hair
* Most M. canis fluoresce, if done carefully
Trichography
* Arthrospores (soap bubbles) surrounding hair shaft, hyphae within hair
In house DTM
* False positives and negatives
External lab fungal culture (± PCR)
* Test of choice/gold standard
Sampling for culture best using a sterile toothbrush = Mackenzie Technique
What is this low and high power microscopy showing?
Broken hairs and destroyed hairs, with spores cuased by dermatophytosis (ringworm)
How can biopsy be used to diagnose dermatophytosis?
- Don’t prep the skin site
- Send tissue with hair follicles
- Deep wedge or excisional for nodular or indurated tissue, (debulk/excise nodules prior to treatment}
- Alert laboratory to differential diagnoses – PAS / other fungal stains
- In cases of nodular dermatophytic disease, biopsy is needed for diagnosis
What is the treatment for dermatophytosis?
- Can spontaneously resolve (12 -20 weeks)
- Should be treated to reduce environmental contamination and zoonosis risk
- Clipping (to remove the spores)
- Controversial (? in long coated breeds) microtrauma may increase infection (can cause subcuticular dermatiopytosis)
- Topical treatment
- Decreases contamination & speeds clinical cure
- Chlorhexidine* / miconazole shampoo (2–3 times a week)
- Enilconazole in dogs (not licensed in cats) every 4 days
- Environmental decontamination - hoovering and destroy bedding
- Systemic therapy
- Necessary to achieve mycological cure
- Itraconazole (cats & dogs), ketoconazole (dogs)
*Note Chlorhexidine scrub or shampoo by itself is not effective
How do you monitor treatment success with dermatophytosis?
Monitor fungal culture every 2 weeks ideally using toothbrush technique
- Start when obvious reduction in clinical lesions
- Require two negative cultures 2 weeks apart to describe mycological cure
- False positives will be noted if continuing high levels of environmental contamination
- False negatives will be seen if very recent topical therapy before sampling
(Once a week sampling used in some rescue catteries to increase throughput)
What are the different species of demodex?
follicular mites and surface mites?
- Follicular mites - long bodied
- Demodex canis (dog)
- Demodex injai (dog)
- Demodex cati (cat)
- Surface mites - short bodied
- Demodex gatoi (cat)
- Demodex cornei (dog) describedbut is considered a variant of D. canis and not a separate species and should not be used
What are the two clinicla syndrome in dogs?
Juvenile onset
* Immature immune system
* Localised (< 6 patches alopecia)
* Generalised (> 6 patches, or includes the feet, often multiple body regions)
Adult onset
* Immunosuppressive disease
* Idiopathic
* Localised becoming generalised
What is the appearance of juvenile onset demedicosis?
What is the treatment?
Localised to generalised patches
* Alopecia
* Scaling
* Blue-grey hyperpigmentation
* Comedones
* Follicular casts
+/- superficial bacterial infection
Mild cases spontaneously resolve
Treat cases of localised disease when
* Significant bacterial infection (antibiotic stewardship) (treat with isoxazolines)
* ‘Accidentally if using isoxazolines for routine flea control
* Not necessary for mild disease
What is the clinical apperance of demodicosis? how is it diagnosed?
Clinical appearance
* Multifocal alopecia with follicular castings
* Comedone formation
* Secondary bacterial infection, often associated with peripheral lymphadenopathy
* Malodour
* Greasiness
Positive deep skin scrapings, hair plucks or biopsy
Reserve biopsy for areas with severe secondary changes (e.g. feet) or dogs with mucinosis (i.e. Sharpei)
What are follicular casts?
What do they mean?
Waht diseaases are the common in?
- Indicates follicular disease
- Common in
- Demodicosis
- Dermatophytosis
- Sebaceous adenitis
- Less often in
- Bacterial folliculitis
- Other diseases
- e.g early ECL
- Can be seen by eye!
How can hair plucks be used for diagnosis of demodicosis?
- Useful for feet & face
- May be painful if hairs not loose – they should be!
- Check the hair roots carefully
- Make sure to use coverslip - need to examine quickly in house, will be gone in 24h
If you see comedones on a dog, what should you do?
always do a deep skin scrape - squeeze the skin
What are the signs of adult-onset demodicosis?
What can it be caused by?
Often generalised
Often secondary bacterial infection
* Papules, pustules, draining sinus tracts, enlarged lymph nodes, +/-pyrexia
* Pruritic or painful
This is most often a manifestation of profound systemic illness – but demodicosis may precede overt signs
Identify and manage underlying disease
* Hyperadrenocorticism
* Hypothyroidism
* Diabetes mellitus
* Systemic neoplasia
* Immunosuppressive therapy
* FIV / FeLV
Idiopathic
* Hereditary mite-specific immune defect?
* Lifelong treatment
* Small number juvenile cases progress to adulthood
What is the treatment for adult onset demodicosis?
- Clip long haired animals, bathe to remove debris
- Treat any secondary bacterial pyoderma
- Treat ANY underlying immunosuppression
- Anti-mite treatments
- Amitraz (Aludex®): licensed (not cats) – not recommended
- Licenced isoxazoline drugs e.g. afoxolaner, flurolaner, sarolaner and lotilaner
- Imidacloprid/moxidectin (Advocate®): licensed, many have questioned the efficacy of this product in more severe cases
- No need for environmental therapy
- Treat until 2-3 consecutive negative skin scrapes taken every 4 weeks
Should you breed from female dogs with generalised juvenile onset demodicosis?
Neuter female dogs with generalised juvenile onset demodicosis
* Increased chance of disease in offspring
* Periparturient reduction in immunity can result in return of disease (demodicosis has a genetic basis and most likely multiple genes are involved)
But what is generalised disease?
* Disease in young dogs that does not self-cure?
* Involvement of more than 6 areas?
* Involvement of any feet?
* A judgement call!
