Scarring or non-scarring (follicular openings present)
patchy or diffuse
if inflammed may lead to permanent loss
beware associated psych morbidity

look for scaling, hair loss, inflammation
don't do hair pull test if hair washed in last 24 hours
think systemic - eg thyroid
consider hair thinning and xs shedding

scaly or not - send scrapings if it is for mycology
remember systemic disease
most common cause - M or FPB - ? see as normal physiology of ageing

If permanent - pschy problems may develop 
Mx - cosmetic aids, psychological assess, support groups

Signs
Minuterised scalp hairs (thin and fine) - male and female patturn baldness 
Exclamation mark hairs - AA
Perifollicular erythema (think lichen planopilaris) 
Dense scarring (think folliculitis decalvans) 
Scaly - fungal, psoriasis, seborrhoeic dermatitis 

''DD - scalp scarring'' - to distinguish from non scarring - no follicular openings, frank scars, fibrosis on histology
Lichen planus (planopilaris - irreversible, patchy, rare, perifollicular erythema)
Folliculitis decalvans (irreversible, inflammation, dense scarring, idiopathic)
Dissecting cellulitis (from acne) - inflammatory nodules, scarring, permanent hair loss, Rx - isotretinoin
Idiopathic

''DD - diffuse non scarring''
hypothyroid or hyper
hypervit A - diet, supplements, retinoids 
Iron-deficiency anaemia (FBC ferritin) (but replacement may not solve)
Warfarin
check free and total testosterone and DHEA - androgen tumour / PCOS

''Trichotillomania''
habit and impulse disorder - feel tense, pull hair, feel gratified ...
may eat hair - trichobezoar
hairs pulled out - short broken hairs present but not easily extracted -
may be from anywhere on body, odd shaped patches, never complete, if extensive may be tonsure shaped
onset in childhood - good prognosis. in adolescence (esp girls) less good may have psych component
check for fungus, DD AA
Rx - hard, refer dermatology, consider psych - CBT/ anti-depressants

Female patturn baldness

Alopecia areata

''Fungal infection (tinea capitis)''
scaly, pustular, inflamed - send to mycology, more in kids
broken hairs
in UK 90% is T tonsurans
may become boggy - kerion - scarring and permanent loss with cervical LN - may need steroids
Mx - oral griseofulvin - >8/52 SE - abdo disturb, headache, nausea, leucopenia, hepatotoxic - check FBC and LFT first (or 4/52 terbinafine - not licensed in UK), but needs mycology result first
topical shampoo etc - may decrease infectivity but doesn't penetrate hair shaft

''Traction alopecia'' - tight braids - may be irreversible

''Chronic zinc deficiency ''- can cause hair loss but rare in UK, usually related to malabsorption

''2ndary syphilis'' - rare cause, patchy

''Telogen effluvium''
xs hair loss (normal 40-80, TE 100-200) - may not be apparent to observer except at frontal hairline, positive hair pull test (take bunch (60 hairs) and gently pull - about 6 should come out (10%) if more test is positive)
think - anaemia, thryoid, drugs
acute - follows sig event eg childbirth or surgery - major episode induces more hairs to go from anagen to telogen
Hair growth - Anagen - growth (2-5yrs), catagen (brief transition 10 days), telogen
(resting lasts 100 days then shed - 10% hairs in telogen), exogen (gone)
up to 50% loss, 
loss for up to 6/12, recovers by 12/12
Mx - reassure ?? Minoxidil if chronic (>6/12 loss)
2nd most common cause of diffuse loss