eMedicine Specialties > Pediatrics: General Medicine > Dermatology
Keratosis Pilaris
Updated: Oct 12, 2009
Introduction
Background
Keratosis pilaris is an extremely common and benign disorder of keratinized hair follicles.1 The disease is characterized by grouped, horny, keratotic follicular papules predominantly located on the extensor surfaces of the proximal limbs, most commonly of the posterolateral upper arms and anterior thighs. It is usually asymptomatic except for its cosmetic appearance. Treatment is marginally effective and only provides temporary relief.2
Although other sites may be involved, keratosis pilaris is most common on the lateral upper arms and upper thighs.
Upon closer examination of keratosis pilaris, the lesions are very evenly spaced. This even distribution is consistent with the follicular origin of this disorder.
Close examination of keratosis pilaris shows keratotic papules associated with hair follicles. Keratinocytes normally shed from the surrounding skin become dust on the floor. Keratinocytes at the follicular orifice are retained, producing these papules.
Bacteria associated with the follicular papules of keratosis pilaris may cause some lesions to become erythematous or pustular.
Pathophysiology
Apparently because of lack of proper desquamation of keratinocytes, the follicular orifice becomes plugged with keratin and results in a keratotic papule. A variable degree of perifollicular erythema occurs.
Frequency
United States
Significant individual variation is observed in the prominence and severity of keratosis pilaris, which affects 42% of the population. Some studies estimate that keratosis pilaris affects 50-80% of all adolescents. The disorder has a familial relationship, which is consistent with autosomal dominant transmission.
Frequency is increased, reported at 74%, in individuals with ichthyosis vulgaris. Many older reports claim an increased incidence with atopic dermatitis, but more recent studies do not demonstrate this association. Hormonal influence may occur because a high prevalence and intensity of keratosis pilaris is noted during puberty and in women with hyperandrogenism.
International
Incidence is similar to that observed in the United States.
Mortality/Morbidity
Keratosis pilaris is a benign disorder; treatment in most cases requires simple reassurance and general skin care recommendations. Many patients find lesions cosmetically unappealing and, therefore, seek treatment. Occasionally, they may become secondarily infected because of scratchy, tight-fitting clothing or abrasive self-therapy, in which case treatment of the infection is necessary. A significant inflammatory component may be present and may be relieved with topical steroid therapy. Treatment of the noninflamed horny papules can be difficult because they have proven resistant to most modes of therapy.
Race
No evidence of racial predilection is noted.
Sex
The inflammatory form of keratosis pilaris is more prevalent in females.
Age
Fifty-one percent of cases are diagnosed in people in the first decade of life, 35% in the second, 12% in the third, and 2% in the fourth.
Clinical
History
- The patient with keratosis pilaris may report groups of keratotic papules, which feel rough and prickly. The patient may describe them as persistent, rough goose bumps. They are not painful or significantly pruritic in most patients.
- About half of all affected patients notice a worsening of symptoms in the winter months.
- These lesions tend to improve after a few years.
Physical
- Keratosis pilaris alba is the more common variant and is characterized by small gray-white papules with a negligible inflammatory component.
- Keratosis pilaris rubra has a significant inflammatory component; thus, patients present with small erythematous papules. More widespread areas of skin are involved. This variation is most conspicuous during the winter months.3
- Observe for small, horny, follicular papules with (ie, rubra) or without (ie, alba) surrounding erythema.
- Most commonly, lesions occur on the posterolateral upper arms and anterior thighs. Less commonly, lesions involve the face, buttocks, and trunk.
- In involved areas, lesions are extensive, monomorphic, and very evenly spaced.
- A fine hair may pierce the papules, or hair may be found coiled up within the keratin plug.
- The keratin plug cannot be expressed with pressure.
Causes
- The etiology is unknown, although keratosis pilaris may be due to a disorder of corneocyte adhesion that prevents normal desquamation in the area around the follicle.
More on Keratosis Pilaris |
 Overview: Keratosis Pilaris |
| Differential Diagnoses & Workup: Keratosis Pilaris |
| Treatment & Medication: Keratosis Pilaris |
| Follow-up: Keratosis Pilaris |
| Multimedia: Keratosis Pilaris |
| References |
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References
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Zouboulis CC, Stratakis CA, Gollnick HP, Orfanos CE. Keratosis pilaris/ulerythema ophryogenes and 18p deletion: is it possiblethat the LAMA1 gene is involved?. J Med Genet. Feb 2001;38(2):127-8. [Medline]. [Full Text].
Further Reading
Keywords
keratosis pilaris alba, keratosis pilaris rubra, goose bumps, hair follicle, keratinized hair follicles, keratotic papule, perifollicular erythema, ichthyosis vulgaris, atopic dermatitis, hyperandrogenism, erythematous papules, corneocyte adhesion, hyperkeratosis, hypogranulosis
