alopecia

Introduction

scalp hair biology
- everyone is born with a fixed number of hair follicles on the scalp that produce hairs throughout life.
- unlike other areas of the body, hairs on the scalp to grow in tufts of 3–4
- anagen phase:
  - hair grows from the base of the follicle at 1cm/month for about 3yrs
- catagen hair:
  - once the hair stops growing it dies but remains in the follicle
- telogen phase:
  - this is a dormant phase and lasts some 3 months after which a new hair follicle starts to grow in a new anagen phase and which then pushes out the old dead hair
- see https://www.dermnetnz.org/topics/hair-loss/
some medications may cause alopecia such as:
- androgens
- chemotherapy agents
- chronic vitamin A toxicity
- Colchicine overdose
- sodium valproate (Epilim)
- clonidine (Catapres) rarely
- isotretinoin (Roaccutane) rarely
some nutritional deficiencies may cause alopecia:
- niacin / nicotinic acid / nicotinamide (vitamin B3)
- biotin (vitamin B7 / vitamin H / coenzyme R)
some toxins may cause alopecia:
- mercury poisoning

Patterns of alopecia

male pattern balding
- see androgenetic alopecia
female pattern hair loss
- a diffuse thinning of scalp hair has a polygenetic inheritance and affects 40% of women by age 50 and 55% by age 80yrs
- often no cause is found but one should consider:
  - thyroid disease
  - polycystic ovary syndrome (PCOS) / polyendocrine metabolic ovarian syndrome (PMOS) (although tends to cause general body hirsutism but may cause scalp thinning) or other androgen disorders
  - congenital adrenal hyperplasia
- DDx includes chronic telogen effluvium which has a different Mx
- see also: https://www.dermnetnz.org/topics/female-pattern-hair-loss/
cicatricial alopecia
- hair loss due to scarring of the skin - hair will not regrow once the follicle is destroyed
- tufted folliculitis
  - doll's hair-like bundling of follicular units
  - surrounding white coloration and scaling around the hair follicles form a “starburst pattern” that is indicative of the fibrosis process
  - there are visible blood vessels in between the hair follicles
  - treat underlying cause
  - may be secondary or primary neutrophilic or lymphocytic depending upon cause
  - burns
  - trauma
  - surgery
  - pemphigus
  - tinea capitis
  - chronic staphylococcal infection
  - chronic lupus erythematosus
  - lichen planopilaris
  - Graham-Little syndrome
  - folliculitis decalvans
  - acne keloidalis nuchae
  - immunobullous disorders
  - dissecting cellulitis
- secondary cicatrical alopecia
  - burns
  - trauma
  - skin infections
    - recurrent scalp folliculitis / acne necrotica
- primary cicatrical alopecias
  - keratosis follicularis spinulosa decalvans
  - perifolliculitis capitis abscendens et suffodiens
  - neutrophilic scarring alopecias
    - folliculitis decalvans
      - accounts for ~11% of scarring alopecias in the USA
      - an inflammation of the hair follicle that leads to bogginess or induration of involved parts of the scalp along with pustules, erosions, crusts, ulcers, and scale
      - begins at a central point and spreads outward, leaving scarring, sores and alopecia
      - probably due to Staph aureus as this is found in most cases
      - first described by Charles-Eugène Quinquaud in 1888
      - usually commences between the late teens and middle adult years and in the US, mainly affects male African Americans
      - no curative Rx as yet but combination therapy of Clindamycin and Rifampicin has been useful
  - lymphocytic scarring alopecias
    - low dose doxycycline 20mg bd as effective and with less side effects than 100mg bd ¹⁾
    - frontal fibrosing alopecia
      - auto-immune; uniform linear band hair loss along the front and sides of scalp hair margin;
      - skin looks pale, shiny, or mildly scarred, without visible hair follicle openings and lacking sunlight damage
      - may be preceded by eyebrow thinning (madarosis)
      - in men, there may be loss of beard and sideburns as initial sign
      - slowly progressive although is self-limiting in most cases after several years. The hair line recedes on average of 1.8-2.6 cm. ²⁾
      - 1st described in Australia in 1994
      - incidence is increasing; mainly post-menopausal caucasian women but can affect a wide range of age/sex/ethnicities
      - may be associated with: hypothyroidism, contact allergy to fragrances or sunscreen use; systemic lupus erythematosus (SLE), rheumatoid arthritis, androgenetic alopecia
    - chronic cutaneous lupus erythematosus
      - need to exclude systemic lupus erythematosus (SLE)
      - more common in white and African American women, esp. 20-40yr olds
      - solitary or multiple variable size lesions occur primarily on sun-exposed areas and on the scalp
    - lichen planopilaris
    - Graham-Little syndrome
      - lichen planus-like skin lesions (probably a variation of this condition)
      - patchy cicatricial alopecia of the scalp
      - https://en.wikipedia.org/wiki/Graham-Little_syndrome
    - central centrifugal alopecia
    - pseudopelade (Brocq)
      - a flesh- to pink-colored, irregularly shaped alopecia that may begin in a moth-eaten pattern with eventual coalescence into larger patches of alopecia
      - most typical location for the first lesion is the vertex. The eyebrows and beard may be impacted
      - https://en.wikipedia.org/wiki/Pseudopelade_of_Brocq
alopecia areata
- sudden appearance of one or more round areas of hair loss
- aka autoimmune alopecia
- affects 1-2% of people over their lifetime and starts in childhood in 50% and before the age of 40yrs in 80%
- appears to have an auto-immune causation and a genetic basis with at least 8 genes detected
- it may be precipitated by viral infection, trauma, hormonal change, or stress
- may be caused by immunodeficiencies such as common variable immunodeficiency (CVID) and coeliac disease
- see also https://www.dermnetnz.org/topics/alopecia-areata/
- DDx includes fungal infections such as tinea capitis
alopecia totalis
- as with alopecia areata but involves the whole scalp and affects 5% of patients with autoimmune alopecia
alopecia universalis
- as with alopecia areata but involves the whole body and affects 1% of patients with autoimmune alopecia
tricotillomania

¹⁾

https://www.news-medical.net/news/20250318/Lower-doses-of-antibiotic-doxycycline-offer-effective-treatment-for-alopecia.aspx

²⁾

https://dermnetnz.org/topics/frontal-fibrosing-alopecia