the hair cycle:

Telogen is the resting phase which lasts approximately 100 days The hair cycle growth phase begins with anagen. For scalp follicles, this phase can last two to five years, with the length of the hair proportional to the duration of anagen. There is then a brief transition phase, catagen, which lasts only 10 days. The resting phase, telogen, lasts around three months, after which the hair is shed (exogen).

  • Follicular openings are normally present in non-scarring hair loss and absent in scarring hair loss

Alopecia Areata

  • localised

  • polygenic autoimmune: associated with atopy/autoimmune disease

  • no apparent inflammation of skin

  • most common cause of patchy hair loss

  • mucosal involvement not feature of alopecia areata

  • can affect any hair: eyelashes, eyebrows, body, nasal

  • weeks to months

  • stable

    • regrowth 6-12/12

Exclamation mark hairs - broken off stubby ends

associated with pitting of nail plate

  • if after puberty >80% regrow hairs

  • recurrence common

  • no specific treatment

    • can try topical dithranol - not first line

    • Diphencyprone; potent contact sensitiser: may be useful in extensive disease

  • not scaly

Pattern hair loss

  • most common

  • combined:

    • genetics

    • action of androgen on hair follicles

Men:

  • bitemporal recession

  • frontal +/- vertex

  • loss of all hair

    • except occipital/temporal margin -> “Hippocratic wreath”

  • Testosterone -> DHEAS

Women:

  • parietal and temporal recession

    • not usually major feature

  • starts from vertex

  • minor hit thinning most common

  • check: acne, hirsuitism, irregular menses

    • androgen excess

  • Hair loss on the occipital scalp is never a feature of female pattern hairless

Skin = noraml

Hair: finer (shorter + red. diameter)

in time becomes vellus and eventually atrophies completely

Management:

  • oral finasteride

    • 1mg po od = propecia (NS)

    • slows hair loss 3/12

    • no action on other androgen targets

    • issues:

      • 2% dec. libido and erectile dysfunction: reversible

    • no evidence for use in female pattern hair loss

  • Topical minoxidil 5% = Regaine/Rogaine (NS)

  • Antiandrogen

    • cypertone

    • fluta

    • cimitadine

  • Wig

  • Surgical

Telogen effluvium

  • transient inc. shedding of normal club hairs from resting scalp follicle

  • normally 40-80 hairs are shed from scalp/day

  • in TE : 100-200 hairs/day

  • inc. patchy hair loss and if severe diffuse thinning

  • reaction pattern to variety of stressors:

    • endocrine (hypothyroid)

    • Nutrition

    • physical

    • psych

    • Tallium/mercury/arsenic

    • drugs

  • second most common cause

  • 6-12 /12 to return to baseline

  • rarely >90%

  • noraml scalp

  • inc. hairs on hair pull

  • Beaus’s lines

  • no infection

  • DDx

    • anaemia

    • thyroid dysfunction

    • drugs

      • FBC, Haematinics, TFTs

Trichotillomania

  • habit and impulse disorder

  • hair loss never complete

  • short, broken hairs are not easily extracted

  • may eat hair -> trichobezoar/hair ball in stomach

  • in children : prognosis = good

  • often in tonsure pattern

  • when children present: exclude fungal infection and allopeica

the hair cycle:

Telogen is the resting phase which lasts approximately 100 days The hair cycle growth phase begins with anagen. For scalp follicles, this phase can last two to five years, with the length of the hair proportional to the duration of anagen. There is then a brief transition phase, catagen, which lasts only 10 days. The resting phase, telogen, lasts around three months, after which the hair is shed (exogen).