Hair Flashcards
1
Q
Androgenetic alopecia pathogenesis
A
- Genetics:
- high concordance in monozygotic twins
- Genetic loci - encodes androgen receptor oestrogen receptor-beta –> aromatase which converts testosterone to oestradiol
- WNT signalling pathway
- Hormones
- androgens initiate, and inhibition of these will arrest progression and partially reverse hair miniaturization
- Males:
- testosterone converted to DHT by 5alpha-reductase (three isoenzymes of these, Type 2 predominantly in scalp and beard, as well as liver and prostate, and type 3 is epidermis and dermis)
- genetic absence of type 2 5alpha reductase prevents development of AGA
- In AGA: DHT and 5alpha-reductase are increased
- DHT responsible for miniaturised hair follicles and hair shafts
- Women:
- family history
- peri-menopausal and menopause
- Children:
- prepubertal
- strong family history
- no evidence for testosterone/precocious puberty
- Increases prostaglandin D2 synthetase as well
2
Q
Androgenetic alopecia male clinical
A
- frontoparietal and frontal recession
- assess via Hamilton or Norwood system
3
Q
Androgenetic alopecia female clinical
A
- diffuse central thinning of the crown with preservation of the frontal hairline
- ‘Christmas tree’ - frontal accenutation of the hair loss
- history of increased hair shedding may precede the clinical appearance
- Assess with Sinclair scale 1-5
- 1 is normal
- 2 - widening of central part line
- 3- widening of the part line with translucency of the hairs at its border
- 4- bald area anteirorly along the part line
- 5 - advanced hair loss
4
Q
Androgenetic alopecia histology
A
- Scalp hairs exist as follicular units composed of 3-5 shaft-producing follicles serviced by a single arrector pili muscle
- As follicles miniaturise, follicular units produce only 1-2 terminal hairs
- once all follicles miniaturise, then baldness is observed
- Normal total number of follicles
- Increased number and % of vellus hairs
- Numerous fibrous streamers
- Increased telogen count
- Uninvolved scalp appears normal
5
Q
Androgenetic alopecia treatment male
A
- Topical minoxidil
- biologic modifier
- 1 ml BD
- Adverse effects: dryness, irritation, ACD
- Initially have shedding of telogen hairs and paradoxical worsening of hairs in first 4-6 weeks
- Oral finasteride
- 1 mg daily
- Type 2 5alpha-reductase inhibitor
- halts hair loss in 90% of patients, and partial regrowth in 65%
- halting medication results in resumption of hair loss
- A/E: loss of libido, reduced ejaculate, erectile dysfunction ~2%
- Prostate cancer reduced, but high dose may increase risk ?unsure if due to extra screening or truly causes
- can affect PSA, adjust PSA by 40-50% more
- Surgical hair replacement
- Oral PGD2 receptor antagonist - setipiprant
6
Q
Androgenetic alopecia treatment female
A
- topical minoxidil
- low to moderate level of evidence
- Oral contraceptive
- Spironolactone
- if fall pregnant on this, feminization of male featus
- Finasteride
- not helpful in post menopausal women
- Dutasteride
- Type 1 and 2 5alpha-reductase inhibitor
- teratogenicity though so not ideal for childbearing women
- may be more effective than finasteride
7
Q
Androgenetic alopecia trichoscopy
A
peri-pilar brown halo, miniaturisation
8
Q
Telogen effluvium background
A
- normal scalp: ~100 000 hair follicles, 90% in anagen phase and 10% telogen
- Telogen lasts for 3 months
- Daily - 50-200 hairs undergo exogen and shed, and 500-1000 are in transitional catagen phase
- Anagen: hair will grow for a few months-years, then becomes telogen and sheds
- Telogen effluvium is when an abnormally large numbers of hairs
9
Q
Telogen effluvium pathogenesis
A
- shedding of the newborn or postpartum
- Chronic telogen effluvium –> women 30-60 years of age, dx of exclusion
- Postfebrile
- Severe infection
- Severe chronic illness
- Stress
- Postsurgical
- Hypothryoidism and other endocrinopathies
- Crash or liquid protein diets
- Drugs
- Discontinuation of OCP
- Retinoids and vitamin A excess
- Anticoagulants - heparin
- Antithyroid
- Anticonvulsants
- Interferon alpha 2b
- Heavy metals
- Beta blockers
- Hair loss begins 3 months after defining event - amount of time that it takes to progress through telogen phase and then be shed
10
Q
Telogen effluvium clinical
A
- Thinning of the hair
- Hair pull - positive for 2 or more telogen hairs
- Forcible pluck - mixture of anagen and telogen, with telogen >20%
- Diagnostic: telogen hairs >20%
- 60 second timed hair count:
- brush hair for 60 seconds over a cloth of a contrasting colour
- usually in excess of 100 hairs
- Prognosis: hair regrowth is expected
- If cause unclear - thyroid, chemistry, FBC, ferritin –> ferritin should be at least 40
- If >6 months - scalp biopsy with horizontal sectioning
- Trichoscopy: hair shafts are of equal diameter
11
Q
Alopecia areata epi
A
- 0.1-0.2%
- overall lifetime risk is 1.7%
- 1/5 report family history
12
Q
Alopecia areata pathogenesis
A
- Genetics
- regulatory T cells
- HLA alleles, IL-2, IL-21 etc
- Immune
- CD8 T cells initial intrafollicular lymphocytes to appear in alopecia areata
- Involvement of interferon gamma - downstream signaling via the JAK pathway
- Autoimmune
- autoantigen from melanocytes which are active during the anagen
- Associated conditions
- Atopy
- Autoimmune thyroid disease, vitiligo, inflammatory bowel disease
- Autoimmune polyendocrinopathy syndrome type 1
- Type 1 diabetes
13
Q
Alopecia areata clinical
A
- Round or oval patches of non-scarring hair loss
- Short exclamation point hairs - particularly at margins of areas of alopecia
- Alopecia totalis: loss of all scalp hair
- Alopecia universalis: scalp and body hair
- Ophiasis: band like pattern of hair loss along the periphery of the temporal and occipital scalp
- Beard involvement
- Reticular variant: recurrent, patchy disease in which the patient experiences hair loss in one area while regrowing in another
- Diffuse variant - widespread thinning, primarily affects the top of the head, white hairs aren’t affected so think they’re going gray. Regrowth may initially be depigmented and then pigment
- Extra-cutaneous:
- Nail pitting
- Trachyonychia
- Brittle nails
- Onycholysis
- Koilonychia
- Onychomadesis
- Dermoscopy: yellow dots in follicular ostium of empty and hair-bearing follicles, exclamation point hairs
14
Q
Alopecia areata histology
A
- Early:
- normal total number of hairs
- peribulbar mononuclear cell infiltrate, affecting terminal anagen and catagen bulbs –> ‘swarm of bees’
- some inflam exocytosis into bulbar epithelium
- increased numbers of terminal catagen and telogen hairs
- increased number of miniaturized hairs
- trichomalacia
- Chronic:
- majority of hairs in catagen or telogen phases
- numerous miniaturised arrest rapidly cycling hairs - ‘nanogen’
- mild peribulbar infiltrate
- Fibrous tracts extending along site of previous follicles in the subcutis
- Inversion anagen:telogen ratio
15
Q
Alopecia areata treatment
A
- topical: steroids, minoxidil, anthralin, azelaic acid, immunotherapy (DCP)
- Intralesional steroids - 2.5-5 mg/ml, repeat every 4-8 weeks, inject at level of mid dermis to target the diseased hair bulbs
- Systemic steroids - pulsed dosing –> 80% respond to his, however 50% relapse with dose reduction or cessation of therapy
- JAK inhibitor: tofacitinib, ruxolitinib
- PUVA
- Excimer laser
- Long term steroids
- Systemic cyclosporin
- Cosmetic
