Alopecia Flashcards
Compare primary and secondary alopecia
- Primary: failure to grow normally
- Secondary: grows normally but subsequently damaged or lost
What are the mechanisms of primary alopecia?
- Lack of stimulation of growth
- Abnormal growth factors
- Elongation of telogen phase
Define true alopecia
Direct damage to the hair follicle unit, leading to loss of the whole hair follicle unit
Define apparent alopecia
Hair shaft damaged but not lostr from hair follicle unit
How should a case of apparent alopecia be investigated?
No damage to hair follicle unit, check this on trichogram. Likely due to pruritus so investigate as pruritus case
Identify the potential causes for true alopecia
- Hair follicle inflammation e.g. folliculitis, furunculosis, bulbitis. Hair follicle unit damaged
- Hair cycle abnormality e.g. endocrine
- Hair morphological abnormalities: hair malformed, breaks off
- Congenital aplasia: never grows
List the lesions commonly associated with alopecia
- Pustules
- Comedones
- Follicular casts
What would pustules associated with alopecia be suggestive of?
- Pyoderma
- Autoimmune disease
What would comedones associated with alopecia be suggestive of?
- Demodicosis
- Dermatophytosis
- Hypothyroidism
- HAC
- Long term glucocorticoid use (iatrogenic Cushings)
What would follicular casts associated with alopecia be suggestive of?
- Follicular disease
- bacterial infection (pyoderma)
- Demodicosis
- Sebaceous adenitis
- Primary keratinisation disorder
- Endocrinopathy
Describe sebaceous adenitis
- Immune mediated attack on sebaceous glands
- Occurs in certain breeds esp. poodles and poodle crosses
What is primary keratinisation disorder?
Body genetically programmed to produce lots of keratin inappropriately
Describe the appearance of follicular casts
- When hair is epilated, comes out in clumps surrounded by keratin
- Can be subtle (1 or 2 hairs) or whole collars
What conditions would you be most suspicous of in an animal with alopecia that started <1yo?
- Demodicosis
- Dermatophytosis
- Superficial pyoderma
- Congenital alopecia
What conditions would you be most suspicious of in an animal with onset of alopecia when middle aged/older?
- Endocrinopathies
- Neoplasia
Give some examples of breed specific hair loss
- Small terriers/boxers: predisposed to HAC
- Dachshunds: pattern baldness
- Doberman: dysplastic hair follicle diseases
Give an example of a cause of alopecia in entire males
Sertoli cell cell tumours
Give an example of a cause of alopecia in entire females
Post-partum telogen defluxion (hair loss after whelping, common for bitches, will grow back)
Give examples of how general history can indicate specific causes of alopecia
- PUPD: HAC
- Weight gain, lethargy: hypoT
- Small hunting dogs: trichophyton infection
- Lesions on owner/in contacts: dermatophytosis, ectoparasites
What aspects of the dermatological history can indicate specific causes of alopecia?
- Hair growth after clipping
- Seasonality
- Response to past treatment
- Pruritus
What conditions would lack of hair regrowth after clipping be suggestive of?
- HypoT
- Post clipping alopecia (unknown cause, common in plush coated dogs, can take extremely long to grow back or never)
What condition would you be suspicious of in a dog with bilaterally symmetrical alopecia, obesity, bradycardia, lethargy and lack of regrowth following clipping?
Hypothyroidism
How do Sertoli cell tumours cause alopecia?
Produce excessive oestrogen causing endocrinopathies
List the differentials for localised alopecia
- Key: Demodicosis, dermatophytosis, superficial pyoderma
- Post-clipping alopecia
- steroid injection/post-vaccine vasculopathy, rabies vaccine
- Tail gland hyperplasia on older male dogs
- Cicatricial alopecia (scarring)
- traction alopecia (top knot too tight on Westies)
List the differentials for multi-focal/diffuse patchy alopecia
- Key: demodicosis, dermatophytosis, superficial pyoderma
- Others: dermatomyositis, sebaceous adenitis, alopecia areata
What is alopecia areata?
An autoimmune condition that causes bulbitis
Explain what is meant by coat colour linked follicular dysplasia
- Colour dilution alopecia
- Paler than normal
- Hairs often weaker and break off leading to alopecia
In all cases of alopecia, what are the top 3 differentials?
- Demodicosis
- Dermatophytosis
- Superficial pyoderma