Hair Loss/Acquired Alopecia

Question 1

What are the different phases of hair growth?

Answer 1

IMAGE

Question 2

What occurs during telogen?

Answer 2

Resting phase

Question 3

What happens during the early anagen phase?

Answer 3

Hair starts to enter subcutis

Question 4

What occurs during late anagen?

Answer 4

Skin layer is thicker with hair follicles in subcutis

Question 5

How is hair growth regulated?

Answer 5

Nutrition - malnutrition, metabolic diseases
Central/systemic hormones - thyroid hormone, glucocorticoids, sex hormones, IGF-1, prolactin, melatonin
Regional - differential response to mediators
Local - hormones, mediators, growth factors, cytokines

Question 6

Define alopecia

Answer 6

Baldness
Absence of hair where it is normally present
Loss of hair

Question 7

Define hypotrichosis

Answer 7

Congenital alopecia

Paucity of hair

Question 8

How do you define the problem of alopecia?

Answer 8

Primary alopecia due to growth failure/problem with follicle
Traumatic alopecia due to pruritis or other mechanical factor
Differentiate with hair pluck and examine under microscope

Question 9

What are the 4 principle methods of hair loss?

Answer 9

Traumatic removal of hair
Damage to follicle
Hair cycle arrest
Malformed/dystrophic/dysplastic/atrophic hair follicles unable to produce normal/any hair

Question 10

What does symmetrical alopecia in the cat typically indicate?

Answer 10

Self-inflicted unless proven otherwise so work up as self-trauma/pruritis

Question 11

How do you refine the problem of alopecia?

Answer 11

Inflammatory vs non-inflammatory

Question 12

What are some non-traumatic inflammatory causes of alopecia?

Answer 12

‘Bystander’ follicular damage

Folliculitis due to follicular infection such as Demodex/Staph/Dermatophytes or sterile folliculitis (rare)

Question 13

What is a non-traumatic non-inflammatory cause of alopecia?

Answer 13

Hair follicle structure/function problems
Endocrinopathies
Coat-colour linked
Miscellaneous hair-cycle/growth problems
Other causes rare

Question 14

How do endocrine diseases impact on the hair cycle?

Answer 14

Dyregulation of the hair cycle or hair cycle arrest due to premature or excessive exogen (Telogen effluvium) or impaired anagen promotion/premature catagen (hyperoestrogenism/hyperthyroidism)

Question 15

What is a key point to remember with endocrine disorders causing alopecia?

Answer 15

Look out for other signs of disease either clinically or on lab findings

Question 16

What is the aetiology of Alopecia X?

Answer 16

Unclear could be endocrine but no consistent hormonal abnormality or reversal of abnormality on successful treatment
Some evidence of abnormal adrenal steroidogenesis and some response to steroidogenesis inhibitor but they are healthy dogs so cosmetic problem only

Question 17

What is the pathogenesis behind colour linked alopecia?

Answer 17

Dark hairs are lost as irregular clumped melanin in hair shaft causing hair to break off in hair shaft

Question 18

What is the pathogenesis behind (recurrent) flank alopecia?

Answer 18

Migration problem with melanocytes and melanin

Question 19

What is the pathogenesis behind follicular dystrophies/dysplasias?

Answer 19

Abnormal contorted irregular thickness hair shaft resulting in broken hairs

Question 20

What is the pathogenesis of pattern alopecia?

Answer 20

Occurs in Staffies and short-coated Chihuahuas as the hairs are miniturised

Question 21

What is the diagnostic approach to self-inflicted traumatic hair loss?

Answer 21

Work up as pruritis

Question 22

What is the diagnostic approach to inflammatory alopecia?

Answer 22

Diagnostic tests to investigate demodecosis, bacterial folliculitis and dermatophytosis

Question 23

What is the diagnostic approach to non-inflammatory alopecia?

Answer 23

Consider endocrine disease first then histopathology if diagnosis required