Approach to alopecia Flashcards
What is alopecia?
The loss or absence of hair
What are the two classifications of alopecia?
Spontaneous: no animal involvement, various causes
Self-induced: animal removes hair, pruritis, psychogenic
How can we be sure an alopecic animal is not pruritic at onset?
- Cutaneous signs of pruritis: feel of the coat, saliva staining
- Trichogram shows broken hair shafts in pruritic animals
Give some examples of conditions that cause symmetrical alopecia
- Alopecia X
- Follicular dysplasia
- Canine recurrent flank alopecia
- Hyperadrenocorticism
- Hypothyroidism
Contagious alopecia would be due to?
Dermatophytosis
What are some examples of causes of alopecia in older dogs?
- Hypothyroidism
- Hyperadrenocorticism
- Neoplasia (e.g. epitheliotropic lymphoma
What are some different characteristics of alopecia that should be used to help with diagnosis?
- Partial/complete
- Regular vs irregular patches
- Asymmetrical vs symmetrical
- Focal/multifocal vs generalised
- Erythema, hyperpigmentation, scaling, comedones, skin atrophy
- Spontaneous vs self induced
What are some inflammatory causes of alopecia?
- Infectious agents e.g. Dermatophytosis
- Parasitic e.g. Demodicosis
- Immune mediated
What are some non-inflammatory causes of alopecia?
- Hair follicle arrest
- Hair synthesis defetcs
Name some examples of hair follicle arrest conditions
- Endocrinopathies
- Alopecia X
- Paraneoplastic alopecia
- Cyclical flank alopecia
- injection alopecia
Name some examples of hair synthesis defect conditions
- Congenital alopecia
- Follicular dysplasia
- Pattern alopecia
- Sebaceous adenitis
What is the most common cause of spontaneous infectious alopecia in dogs and cats?
Bacterial folliculitis
Name the bacteria which causes bacterial folliculitis
Staphylococcus pseudintermedius
How does bacterial folliculitis present?
Focal to multifocal patches of alopecia
+/- pustules, crusts
Most causes of ringworm are in…?
young or immunocompromised animals
What will be observed in the examination of an animal with ringworm?
- 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
Give some examples of methods use to diagnose ringworm?
- Wood’s lamp examination
- Trichography
- In house dermatophyte test medium
- External lab fungal culture (gold standard)
- Mackenzie toothbrush sampling
- Biopsy
Describe a wood’s lamp examination for ringworm
- Warm for 5-10 mins, expose hair for 3-5 mins
- Apple green fluorescence of hair
What will be seen on a Trichogram if ringworm is present?
Arthrospores (soap bubbles) surrounding hair shaft, hyphae within hair
Describe a Mackenzie toothbrush sample for ringworm
- Use a cheap new toothbrush with nylon bristles
- Brush the affected areas on the animal until some hair and scale connected.
- Submit the whole toothbrush (with or without the handle removed) to the lab or inoculate onto fungal culture medium
Which special stain is used for fungal hypahe?
Silver stains
Even though ring worm may spontaneously resolve, why should it be treated?
Due to zoonotic risk and to reduce environmental contamination
Describe treatment options for ringworm
- Clipping
- Topical treatment with chlorhexidine or a lime sulphur dip
- Environmental decontamination: isolate animal, destroy bedding, daily vacuuming and disinfection
Which systemic treatments can be used to treat ringworm?
- Itraconazole: effective in dogs and cats
- Ketoconazole: licensed in dogs
How can ringworm treatment success be monitored?
- Monitor fungal culture every 2 weeks ideally using toothbrush technique
- Start when obvious reduction in clinical lesions
- Require two negative cultures 2 weeks apart
Nodular Dermatophytosis affects which cat breed?
Persian
Nodular dermatophytosis is also known by which name?
Pseudomycetoma
Describe the features of Pseudomycetoma
- Subcutaneous form of dermatophytosis
- Usually accompanied by typical dermatophyte signs unless treated
- 3-6 months of daily treatment
What is a parasitic cause of spontaneous alopecia?
Demodex/Demodicosis
Name the 3 long bodied Demodex spp seen in dogs and cats
- Demodex canis (dog)
- Demodex injai (dog)
- Demodex cati (cat)
Name the short bodied Demodex spp seen in cats
Demodex gatoi
What are the two clinical syndromes of canine demodicosis?
Juvenile onset
Adult onset
Describe the features of juvenile onset canine demodicosis
- Immature immune system
- Localised (<6 patches of alopecia)
- Generalised (includes body region – feet, head)
- Mild cases spontaneously resolve
What are the clinical signs of juvenile onset canine demodicosis?
- Alopecia
- Scaling
- Blue-grey hyperpigmentation
- Comedones
- Follicular casts
- +/- Secondary bacterial infection
How is juvenile onset canine demodicosis diagnosed?
Clinical appearance:
- Multifocal alopecia with follicular castings
- Comedone formation
- Secondary bacterial infection, often associated with peripheral lymphadenopathy
- Malodour
- Greasiness
Positive skin scrapings, hair plucks or biopsy
Follicular casts are common in which 3 conditions?
Demodicosis
Dermatophytosis
Sebaceous adenitis
Skin scrapings must always be done if what are seen?
Comedones
Describe the features of adult onset canine demodicosis
- Immunosuppressive disease
- Idiopathic
- Often generalised
- Require aggressive treatment
What are the clinical signs of adult onset canine demodicosis?
- Papules, pustules, draining sinus tracts, enlarged lymph nodes, +/-pyrexia
- Pruritic or painful
Give some examples of underlying disease which may contribute to adult onset canine demodicosis?
- Hyperadrenocorticism
- Hypothyroidism
- Diabetes mellitus
- Systemic neoplasia
- Immunosuppressive therapy
- FIV / FeLV
Describe some treatment methods for canine demodicosis
- Clip long haired animals, bathe to remove debris
- Treat any secondary bacterial pyoderma
- Treat ANY underlying immunosuppression
- Anti-mite treatments e.g. amitraz
- Treat until 2-3 consecutive negative skin scrapes taken every 4 weeks
- Spey dogs with generalised juvenile onset demodicosis
Name some examples of immune mediated spontaneous alopecia
- Alopecia areata
- Dermatomyositis
- Sebaceous adenitis
What are some indications for taking a skin biopsy?
- Nodules and plaques and any suspected neoplastic lesion
- Vesicular lesions
- Ulcerative disease processes or unresolving ulcers
- Lesions failing to respond to rational therapy
- Unusual, severe or widespread disease
- Alopecic diseases (rule out parasitic, endocrine and infectious causes)
How do you select the right lesion to biopsy?
- Primary lesions where possible
- Intact epidermis
- Take enough samples to represent disease process, ideally >3 (5-6)
Where would you take skin biopsy’s from an animal with suspected non-inflammatory alopecia
e.g. 4 biopsies from the middle of the non-inflamed alopecia, 1 from the edge and 1 from an apparently normal part of the skin
Where would you take skin biopsy’s from an animal with suspected inflammatory alopecia
3 biopsies from the expanding edge of the lesion, 2 from the middle of the alopecia and 1 from an apparently normal part of the skin
