Alopecia areata is a chronic, inflammatory condition that affects hair follicles. It leads to hair loss with preservation of the hair follicle (non-scarring alopecia). It most commonly affects the scalp and facial hair (beard mainly but eyebrows and eyelashes may be affected too). The pattern of hair loss is usually patchy with well demarcated areas.
It is a relatively common condition, affecting 1 in 1000 people in the UK. Males are more commonly affected than females.
🏃♀️ Physiology
There are 3 phases to the normal growth cycle:
- Anagen phase - this is the phase of active growth. It can be split into the proanagen and metanagen phases. The proanagen phase sees the proliferation of the follicle progenitor cells. Once the shaft appears on the skin surface it has reached the metanagen phase. It lasts 2-6 years. At any given time, around 85% of our hair is in the anagen phase.
- Catagen phase - this is the phase of follicular regression. In this phase the hair follicle undergoes apoptosis and loses 1/6th of its diameter. It lasts around 3 weeks. At any given time, around 1-2% of our hair is in the catagen phase.
- Telogen phase - this is the resting phase. The follicle is dormant and growth does not occur. It may last for variable amounts of time depending on where in the body it occurs. At any given time, around 10-15% of our hair is in the telogen phase.
Pathophysiology
We are not too sure about the aetiology of alopecia areata. It is an autoimmune disease in which T-lymphocytes attack the hair follicles in the anagen phase of the hair follicle. The hair follicle is not destroyed but the shaft of the hair is.
As mentioned, we are unsure what causes it but there are certain factors we can link to the disease:
- Genetic factors - there is an association with alopecia areata and HLA class II alleles. Down’s syndrome is also linked to an increased risk.
- Lifestyle factors - smoking is also linked to increased risk.
- Neuogenic factors - alterations in the peripheral nervous system may change the release of neuropeptides and influence inflammatory reactions leading to the destruction of the hair shaft.
⚠️ Risk factors
- Thyroid disease
- Type 1 diabetes
- Pernicious anaemia
- Vitiligo
- Family history of alopecia areata
😷 Presentation
- Hair loss - the hair loss is abrupt (occurs within weeks). It most commonly affects the scalp or beard but any hair-bearing skin may be involved. It is patchy, producing circular or oval areas of hair loss (it may be diffuse but this is uncommmon). The alopecia is non-scarring and therefore the follicles are retained.
- Ophiasis pattern - this is when there is hair loss on the back and sides (occipital and temporal regions) but not on top.
- Sisaipho or ophiasis inversus pattern - this is the opposite of ophiasis pattern. Here there is loss at the vertex (the top of the head) but there is occipital and temporal sparing. It looks similar to androgenic alopecia.
- Exclamation mark hairs - this is when the hairs are thinner at the proximal end and blunt on the distal end.
- Overnight greying - this is when there is loss of the pigmented hairs but the white hairs are spared.
- Nail changes - such as onycholysis, beau lines, nail pitting. It is more common in those with severe disease
There may be certain patterns of hair loss seen, such as:
🔢 Classification
We can categorise alopecia areata by the extent of hair loss:
- Patchy alopecia areata
- Alopecia totalis - this is when there is total loss of hair on the scalp.
- Alopecia universalis - this is when there is hair loss over the entirety of the body.
We can also classify it by the severity of hair loss:
- Mild - patchy and <25% of the scalp.
- Moderate - patchy and 25-50% of the scalp.
- Severe - >50% of the scalp involved.
🔍 Investigations
⭐️ Alopecia areata is a clinical diagnosis based on examination.
- Pull test - this is when a small section of hair (~50 hairs) is pulled and they are tugged firmly. The test is positive if >3 hairs are pulled from the scalp.
🧰 Management
- Signs of hair regrowth - no treatment is necessary.
- No regrowth but the amount of hair affected is limited and stable and the patient is not distressed - watchful waiting.
- No regrowth but patient wishes for treatment - potent topical steroids may be trialled for 3 months:
- 🥇 Betamethasone valerate 0.1%
- 🥇 Fluocinolone acetonide 0.025%
- 🥇 Hydrocortisone butyrate 0.1%
- 🥇 Colbetasol proprionate 0.05%
💡 A referral to dermatology may be warranted and they may provide additional first-line options.
Let’s look at some of the specialist options that may be available:
- Intralesional corticsteroids
- Oral corticosterois
- Topical immunotherapy - causes a low-grade allergic contact dermatitis which causes an immune response that induces hair regrowth.
- Immunosuppressants - such as ciclosporin or methotrexate.
- Topical minoxidil
- Dithranol
- Baricitnib - an oral JAK inhibitor.
- Psoralen plus ultraviolet A (PUVA)
Patients should also be advised on cosmetic options to camouflage the hair loss (such as styling, keratin microfibres, hair extensions, tattooing, covering up etc.). Although none of these options can be financed through the NHS.
A referral to dermatology should be made in the following instances:
- Uncertain diagnosis.
- Child, pregnant woman or breastfeeding woman affected.
- Refractory to primary care options.
- Patient declines topical corticosteroids but wishes for medical treatment.
This is a type of alopecia caused by premature shedding of hair follicles that are in the resting phase (telogen phase) of hair growth. It results in diffuse, non-scarring hair loss but does not progress to complete baldness.
Pathophysiology
In telogen effluvium, the telogen phase predominates which leads to premature shedding of the resting hair follicles. The shedding is diffuse but no scarring takes place.
Causes of telogen effluvium include:
- Endocrine - hypothyroidism and hyperthyroidism.
- Drugs - retinoids, antithyroid drugs, anticonvulsants, NSAID's, antidepressants, discontinuation of oral contraceptives.
- Nutritional - zinc, iron, riboflavin, vitamin D deficiencies.
- Stress - severe febrile illness, emotional stress, haemorrhage (e.g., trauma, major surgery)
- Infectious - typhoid, malaria, HIV, tuberculosis, syphilis
- Other - telogen gravidarum (usually 3 months postpartum), autoimmune (e.g., SLE)
😷 Presentation
- Thinning of the hair - this may limited to one area or all over. The top of the scalp is most commonly affected. Density is reduced by <50% though and does not progress to complete baldness.
🔍 Investigations
- Pull test - positive.
- Trichogram - >25% of hairs in the telogen phase.
🧰 Management
- Treat underlying condition
