Hair Loss/Acquired Alopecia Flashcards
What are the different phases of hair growth?
IMAGE
What occurs during telogen?
Resting phase
What happens during the early anagen phase?
Hair starts to enter subcutis
What occurs during late anagen?
Skin layer is thicker with hair follicles in subcutis
How is hair growth regulated?
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
Define alopecia
Baldness
Absence of hair where it is normally present
Loss of hair
Define hypotrichosis
Congenital alopecia
Paucity of hair
How do you define the problem of alopecia?
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
What are the 4 principle methods of hair loss?
Traumatic removal of hair
Damage to follicle
Hair cycle arrest
Malformed/dystrophic/dysplastic/atrophic hair follicles unable to produce normal/any hair
What does symmetrical alopecia in the cat typically indicate?
Self-inflicted unless proven otherwise so work up as self-trauma/pruritis
How do you refine the problem of alopecia?
Inflammatory vs non-inflammatory
What are some non-traumatic inflammatory causes of alopecia?
‘Bystander’ follicular damage
Folliculitis due to follicular infection such as Demodex/Staph/Dermatophytes or sterile folliculitis (rare)
What is a non-traumatic non-inflammatory cause of alopecia?
Hair follicle structure/function problems Endocrinopathies Coat-colour linked Miscellaneous hair-cycle/growth problems Other causes rare
How do endocrine diseases impact on the hair cycle?
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)
What is a key point to remember with endocrine disorders causing alopecia?
Look out for other signs of disease either clinically or on lab findings
What is the aetiology of Alopecia X?
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
What is the pathogenesis behind colour linked alopecia?
Dark hairs are lost as irregular clumped melanin in hair shaft causing hair to break off in hair shaft
What is the pathogenesis behind (recurrent) flank alopecia?
Migration problem with melanocytes and melanin
What is the pathogenesis behind follicular dystrophies/dysplasias?
Abnormal contorted irregular thickness hair shaft resulting in broken hairs
What is the pathogenesis of pattern alopecia?
Occurs in Staffies and short-coated Chihuahuas as the hairs are miniturised
What is the diagnostic approach to self-inflicted traumatic hair loss?
Work up as pruritis
What is the diagnostic approach to inflammatory alopecia?
Diagnostic tests to investigate demodecosis, bacterial folliculitis and dermatophytosis
What is the diagnostic approach to non-inflammatory alopecia?
Consider endocrine disease first then histopathology if diagnosis required
