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Keratosis pilaris is a very common form of dry skin characterised by hair follicles plugged by scale.
Keratosis pilaris is due to abnormal keratinisation of the lining of the upper portion of the hair follicle (the follicular infundibulum). Scale fills the follicle instead of exfoliating.
The tendency to keratosis pilaris has genetic origins, with autosomal dominant inheritance. This means that up to half of the children of an affected individual may display signs of keratosis pilaris to a variable degree.
Keratosis pilaris-like lesions can arise as a side effect of targeted cancer therapies such as vemurafenib.
Keratosis pilaris affects up to half of normal children and up to three quarters of children with ichthyosis vulgaris (a dry skin condition due to filaggrin gene mutations). It is also common in children with atopic eczema.
Although most prominent during teenage years, and least common in the elderly, it may occur in children and adults of all ages.
Keratosis pilaris most often affects the outer aspect of both upper arms. It may also occur on the thighs, buttocks and sides of the cheeks, and less often on the forearms and upper back. The distribution is symmetrical.
The scaly spots may appear skin coloured, red (keratosis pilaris rubra) or brown (hyperpigmented keratosis pilaris). They are not itchy or sore.
Keratosis pilaris tends to be more prominent at times of low humidity, such as in the winter months.
Keratosis pilaris atrophicans refers to uncommon forms of keratosis pilaris in which there are scar-like follicular depressions and loss of hair. These include:
Keratosis pilaris is a clinical diagnosis.
Biopsy reveals:
No cure is available for keratosis pilaris. The following may be useful:
Keratosis pilaris may become less obvious in time. Atrophy or scarring with hair loss is permanent.
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