Localised alopecia

Alopecia areata is a common form of hair loss. It is seen in 2% of patients attending the average dermatology clinic in the United Kingdom. There may be small patches of hair loss or the whole scalp may be affected. Resolution occurs in a few months or the condition may persist for years. There may be slight inflammation of the skin in the affected areas—in keeping with the possibility of an underlying immune reaction against the hair follicles. There is also an association with autoimmue disease and atopy.

In the affected areas the follicles are visible and empty. The hairs about to be lost have an "exclamation mark" appearance and in some areas that are resolving, fine vellus hairs are seen. Patches commonly occur on the scalp, face, or eyebrows. In alopecia totalis, the whole head is involved, and in alopecia universalis hair is lost from the whole of the body.

In many patients, particularly if it is a first episode, regrowth occurs within a few months with fine pale hairs appearing first, being replaced by normal adult hair. In older patients, non-pigmented hair may persist in previous patches of alopecia. Factors associated with a poor prognosis are:

(1) Repeated episodes of alopecia

(2) Very extensive or complete hair loss (alopecia totalis)

(3) Early onset before puberty

(4) In association with atopy

Differential diagnosis includes trauma from the habit of plucking hair (trichotillomania) in mentally disturbed patients and traction alopecia from tight hair rollers or hair styles that involve tension on the hair. In fungal infections (tinea capitis) there is scaling and broken hairs. Fungal spores or hyphae are visible in hair specimens on microscopy.

Inflammation is present with loss of hair follicles in lupus erythematosus and lichen planus.

Treatment

An initial limited area of alopecia areata in adult life can be expected to regrow and treatment is generally not needed. Treatments that are carried out include:

(1) Injection of triamcinolone diluted with local anaesthetic which usually stimulates localised regrowth of hair. Unfortunately it often falls out again and there is a risk of causing atrophy. Topical steroid lotion can be used but results are variable.

Causes of diffuse non-scarring alopecia

Androgenetic alopecia

• Female pattern

Endocrine-thyroid disease (hypothyroidism and hyperthyroidism)

• Hypopituitarism

Diabetes mellitus

Stress

• Postoperative

• Postfebrile

telogen effluvium

Drugs

• Anticoagulants

• Antithyroid agents

• Ciclosporin j

anagen effluvium

Erythrodermic skin disease

Psoriasis

Eczema

• Inflammatory

• Protein malnutrition

• Iron deficiency

Alopecia areata

Alopecia areata, showing exclamation mark hairs

Alopecia areata

Alopecia areata, showing exclamation mark hairs

Alopecia totalis

Trichotillomania

Traction alopecia

Trichotillomania

Traction alopecia

(2) Ultraviolet light or psoralen with ultraviolet A can give good, if transient, results in a few patients but it has little effect in the majority. It may act by suppressing an immune reaction around the hair root.

(3) Induced contact dermatitis and irritants are occasionally effective. Cantharadin and dithranol have been used for many years as irritants. Primula leaves or chemicals

(for example, diphencyprone) can be applied to produce an acute contact dermatitis. The mechanism by which acute inflammation stimulates hair growth is not understood.

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