Introduction
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.
Clinical
History
Keratosis pilaris (KP) patients often report a rough texture (gooseflesh appearance) and overall poor cosmetic appearance of their skin. Eruptions are usually asymptomatic, except for occasional pruritus. Many people with KP are unaware the skin condition has a designated medical term or that it is treatable. In general, KP is often cosmetically displeasing but, medically, is completely harmless. Keratosis pilaris is frequently noted in otherwise healthy, asymptomatic patients visiting dermatologists and other physicians for unrelated skin conditions.
Physical
Physical findings of keratosis pilaris (KP) are limited to the skin. Upon gross examination, the skin of the outer-upper arms and thighs is frequently affected. The skin is described as chicken skin or goose bumps. Often, 10-100 very small, slightly rough bumps are scattered in an area. Palpation may reveal a fine, sandpaperlike texture to the area. Some of the bumps may be slightly red or have an accompanying light-red halo, indicating inflammation. In some instances, scratching away the surface of some bumps may reveal a small, coiled hair.
Small (up to 1-2 mm) folliculocentric keratotic papules are noted (see Media File 1). These are small bumps centered on small hair follicles. Some associated inflammation (erythema) may be present, and lesions may be the color of the skin. Often, a small, coiled hair can be seen beneath the papule. In other instances, a keratin plug or pimplelike material may be expressed from each bump. Pustules and cysts are fairly rare.
Commonly involved areas include posterolateral upper arms (see Media File 2), anterior thighs, buttocks, and facial cheeks. The single most characteristic area in KP is the upper-outer arms.
Causes
The etiology of keratosis pilaris (KP) is not fully known. The definite association of hyperkeratinization has been established. Of persons affected, 50-70% have a genetic predisposition. Dry skin conditions seem to exacerbate the disease. Symptoms generally tend to worsen in winter and improve in summer. Common associations include a family history of KP, ichthyosis, or atopic dermatitis.4 KP is more common in siblings and in twins.
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| Multimedia: Keratosis Pilaris |
| References |
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References
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Augustine M, Jayaseelan E. Erythromelanosis follicularis faciei et colli: relationship with keratosis pilaris. Indian J Dermatol Venereol Leprol. Jan-Feb 2008;74(1):47-9. [Medline].
Poskitt L, Wilkinson JD. Natural history of keratosis pilaris. Br J Dermatol. Jun 1994;130(6):711-3. [Medline].
Mevorah B, Marazzi A, Frenk E. The prevalence of accentuated palmoplantar markings and keratosis pilaris in atopic dermatitis, autosomal dominant ichthyosis and control dermatological patients. Br J Dermatol. Jun 1985;112(6):679-85. [Medline].
Jackson JB, Touma SC, Norton AB. Keratosis pilaris in pregnancy: an unrecognized dematosis of pregnancy?. W V Med J. Jan-Feb 2004;100(1):26-8. [Medline].
Kragballe K, Steijlen PM, Ibsen HH, van de Kerkhof PC, Esmann J, Sorensen LH, et al. Efficacy, tolerability, and safety of calcipotriol ointment in disorders of keratinization. Results of a randomized, double-blind, vehicle-controlled, right/left comparative study. Arch Dermatol. May 1995;131(5):556-60. [Medline].
Novick NL. Practical management of widespread, atypical keratosis pilaris. J Am Acad Dermatol. Aug 1984;11(2 Pt 1):305-6. [Medline].
Bielan B. What's your assessment? Keratosis pilaris. Dermatol Nurs. Aug 2004;16(4):357-8. [Medline].
Lateef A, Schwartz RA. Keratosis pilaris. Cutis. Apr 1999;63(4):205-7. [Medline].
Further Reading
Keywords
keratosis pilaris, keratosis pilaris treatment, KP, hyperkeratosis, folliculocentric keratotic papules, follicular keratotic papules, atopic dermatitis, ichthyosis vulgaris, excessive accumulation of keratin, benign skin lesion, gooseflesh appearance, erythema, chickenskin bumps, chicken skin, and goosebumps.
