Alopecia Flashcards
What is primary alopecia
Failure to grow normally
Secondary alopecia
Grows normally
Subsequently damaged
True alopecia
Direct damage to hair follicle unit
* Loss of whole hair follicle unit
Apparent alopecia
Hair shaft is damaged but not lost from hair follicle unit
Hair is cropped short
Anagen phase
Growth phase
Fat bulb
Catagen phase
Intermediate
Telogen phase
Resting
Skinny bulb
Causes of alopecia
Congenital aplasia - hair never growth
Hair follicle inflammation
Hair cycle abnormality - endocrine
Hair morphological abnormalities
Species considerations for alopecia
Ringworm: very common in cattle, horses, cat, hedgehogs
Demodicosis, pyoderma – very common in dogs
Occult sarcoids – common in horses
Age considerations for alopecia
Immature animal:
□ Infections (demodicosis/ dermatophytosis/ superficial pyoderma) - common
□ Congenital alopecia - rare
Middle-aged/older: endocrinopathies, neoplasia, demodicosis
Sex considerations for alopecia
Entire female guinea-pig:
□ Ovarian neoplasia -> alopecia
Entire male dog:
□ Sertoli cell tumours -> oestrogen production
Breed considerations for alopecia
Small terriers/boxers:
□ Predisposed to hyperadrenocorticism (HAC)
Boxers, bulldogs:
□ Predisposed to recurrent flank alopecia
Dachshunds:
□ Pattern baldness
Staffies/bulldogs/Shar Peis:
□ Predisposed to demodicosis
History considerations for alopecia
○ Evidence contagion/zoonosis?
Dermatophytosis
Ectoparasites
○ Small hunting dogs (eg JRT)?
Trichophyton infection (rodent/hedgehog contact)
○ PUPD, polyphagia?
Suggestive of HAC (dog)
○ Weight gain, lethargy ?
Suggestive of hypothyroidism (dog)
○ Pruritic?
If ‘yes’, investigate as per pruritus
Localised alopecia conditions
Dermatophytosis
Pyoderma
Demodicosis
Multifocal alopecia conditions
Dermatophytosis
Pyoderma
Demodicosis
Symmetrical/diffuse alopecia conditions
Dermatophytosis
Pyoderma
Demodicosis
Endocrinopathies
Pattern alopecias
Follicular dysplasias
Trace element deficiency
Tests to rule out differential diagnoses
Skin scrapings
Wood’s lamp
Trichograms
What does skin scrapings rule out?
Demodicosis
What does Wood’s lamp rule out?
Dermophytosis
What do you look at on a trichogram?
Bulb
□ Stage of growth?
Telogen may predominate in endocrine disease
Shaft
□ Large melanin clumps?
E.g. in colour dilution alopecia (dog)
□ Dermatophyte arthrospores/hyphae?
□ Follicular casts?
E.g. sebaceous adenitis (dog)
Distal tip
□ Broken? Traumatic damage/pruritus
