Alopecia

Question 1

What is primary alopecia

Answer 1

Failure to grow normally

Question 2

Secondary alopecia

Answer 2

Grows normally
Subsequently damaged

Question 3

True alopecia

Answer 3

Direct damage to hair follicle unit
* Loss of whole hair follicle unit

Question 4

Apparent alopecia

Answer 4

Hair shaft is damaged but not lost from hair follicle unit
Hair is cropped short

Question 5

Anagen phase

Answer 5

Growth phase
Fat bulb

Question 6

Catagen phase

Answer 6

Intermediate

Question 7

Telogen phase

Answer 7

Resting
Skinny bulb

Question 8

Causes of alopecia

Answer 8

Congenital aplasia - hair never growth
Hair follicle inflammation
Hair cycle abnormality - endocrine
Hair morphological abnormalities

Question 9

Species considerations for alopecia

Answer 9

Ringworm: very common in cattle, horses, cat, hedgehogs
Demodicosis, pyoderma – very common in dogs
Occult sarcoids – common in horses

Question 10

Age considerations for alopecia

Answer 10

Immature animal:
□ Infections (demodicosis/ dermatophytosis/ superficial pyoderma) - common
□ Congenital alopecia - rare
Middle-aged/older: endocrinopathies, neoplasia, demodicosis

Question 11

Sex considerations for alopecia

Answer 11

Entire female guinea-pig:
□ Ovarian neoplasia -> alopecia
Entire male dog:
□ Sertoli cell tumours -> oestrogen production

Question 12

Breed considerations for alopecia

Answer 12

Small terriers/boxers:
□ Predisposed to hyperadrenocorticism (HAC)
Boxers, bulldogs:
□ Predisposed to recurrent flank alopecia
Dachshunds:
□ Pattern baldness
Staffies/bulldogs/Shar Peis:
□ Predisposed to demodicosis

Question 13

History considerations for alopecia

Answer 13

○ 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

Question 14

Localised alopecia conditions

Answer 14

Dermatophytosis
Pyoderma
Demodicosis

Question 15

Multifocal alopecia conditions

Answer 15

Dermatophytosis
Pyoderma
Demodicosis

Question 16

Symmetrical/diffuse alopecia conditions

Answer 16

Dermatophytosis
Pyoderma
Demodicosis
Endocrinopathies
Pattern alopecias
Follicular dysplasias
Trace element deficiency

Question 17

Tests to rule out differential diagnoses

Answer 17

Skin scrapings
Wood’s lamp
Trichograms

Question 18

What does skin scrapings rule out?

Answer 18

Demodicosis

Question 19

What does Wood’s lamp rule out?

Answer 19

Dermophytosis

Question 20

What do you look at on a trichogram?

Answer 20

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