Excerpt from Keratosis Pilaris

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Background

Keratosis pilaris (KP) is a genetic disorder of keratinization of hair follicles of the skin. It is an extremely common benign condition that manifests as small, rough folliculocentric keratotic papules, often described as chicken bumps, chicken skin, or goose bumps, in characteristic areas of the body, particularly the outer-upper arms and thighs. Although no clear etiology has been defined, KP is often described in association with other dry skin conditions such as ichthyosis vulgaris, xerosis, and, less commonly, with atopic dermatitis, including conditions of asthma and allergies. See Ichthyosis Vulgaris, Hereditary and Acquired and Atopic Dermatitis for more information.

KP affects nearly 50-80% of all adolescents and approximately 40% of adults. It is frequently noted in otherwise asymptomatic patients visiting dermatologists for other conditions. Most people with KP are unaware the condition has a designated medical term or that it is treatable. In general, KP is frequently cosmetically displeasing but medically harmless.

Overall, KP is described as a condition of childhood and adolescence. Although it often becomes more exaggerated at puberty, it frequently improves with age. However, many adults have KP late into senescence. Approximately 30-50% of patients have a positive family history. Autosomal dominant inheritance with variable penetrance has been described.

Seasonal variation is sometimes described, with improvement of symptoms in summer months. Dry skin in winter tends to worsen symptoms for some groups of patients. Overall, KP is self-limited and, again, tends to improve with age in many patients. Some patients have lifelong KP with periods of remissions and exacerbations. More widespread atypical cases may be cosmetically disfiguring and psychologically distressing.

Pathophysiology

Keratosis pilaris (KP) is a genetically based disorder of hyperkeratinization of the skin. An excess formation and/or buildup of keratin is thought to cause the abrasive goose-bump texture of the skin. In these patients, the process of keratinization (the formation of epidermal skin) is faulty. One theory is that surplus skin cells build up around individual hair follicles. The individual follicular bumps are often caused by a hair that is unable to reach the surface and becomes trapped beneath the keratin debris. Often, patients develop mild erythema around the hair follicles, which is indicative of the inflammatory condition. Often, a small, coiled hair can be seen beneath the papule. Not all the bumps have associated hairs underneath. Papules are thought to arise from excessive accumulation of keratin at the follicular orifice.

Frequency

International

Keratosis pilaris (KP) is overall a very common condition and is present worldwide. KP affects 50-80% of adolescents and approximately 40% of adults worldwide.

In India and other countries, a specific condition called erythromelanosis follicularis faciei et colli is described. This is an unusual condition with a possible genetic or other relationship to KP. Erythromelanosis follicularis faciei et colli is characterized by the triad of hyperpigmentation, follicular plugging, and erythema of the face and neck.^{1, 2}

Mortality/Morbidity

Keratosis pilaris (KP) is not associated with increased mortality or morbidity. Often, patients are bothered by the cosmetic appearance of their skin and its rough, gooseflesh texture. KP is present in otherwise healthy individuals and does not have any long-term health implications.

Race

Keratosis pilaris (KP) has no widely described racial predilection or predominance. It is commonly noted worldwide in persons of all races.

Sex

Both sexes are affected by keratosis pilaris (KP), but females may be affected more frequently than males.³

Age

Age of onset of keratosis pilaris (KP) is often within the first decade of life; symptoms particularly intensify during puberty. However, KP may manifest in persons of any age and is common in young children. Some authorities believe individuals can outgrow the disorder by early adulthood, but often this is not the case.

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