Keratosis Pilaris at a Glance
- Common condition of keratotic follicular plugging with variable erythema.
- Mainly involves cheeks and extensor arms and thighs.
- Two main patterns—(1) early childhood onset and (2) adolescent onset.
- Usually improves gradually over years.
- Nonspecific histology of follicular orifice distended by keratin plug.
- Variable response to keratolytics.
- Erythromelanosis follicularis faciei et colli (EFFC): marked erythema and hyperpigmentation.
- Keratosis rubra pilaris (KRP): erythema not limited to perifollicular area, may be same as EFFC.
Follicular keratosis refers to orthokeratosis involving the follicular ostium and infundibulum. Horny plugs protrude from the orifices, producing a rough sensation on palpation of the skin. It may be isolated [keratosis pilaris (KP)] or associated with other pathologic processes, including follicular inflammation, atrophy, scarring, and alopecia [keratosis pilaris atrophicans (KPA)]. These are reaction patterns that occur alone or as part of a wide variety of syndromes.
Typical KP is a common condition of keratotic follicular plugging with varying degrees of surrounding erythema. Sometimes, the erythema is so striking that it is the main complaint. The clinical expression of KP varies from subtle to conspicuous, which, along with possible racial differences, may explain the great range of reported prevalences, from 1% to 42%.1–4 It involves most commonly the extensor aspects of the upper arms (Fig. 87-1) and thighs as well as the face but may rarely be more extensive, extending to the distal limbs and the trunk. There seem to be two patterns. In early childhood, the face and arms are mainly affected and gradual improvement is seen in most cases by later childhood or adolescence. In the other pattern, the onset is in teenage years, and the extensor arms and legs are predominantly involved. It usually improves by the mid-20s. However, in both patterns, the condition may be persistent into later adult life.5 The histopathologic pattern in skin biopsy specimens is nonspecific, simply showing the follicular orifice distended by a keratin plug.
Keratosis pilaris in a characteristic distribution on upper outer arm in a patient with ichthyosis vulgaris.
Treatment is usually with various keratolytics, from simple urea, lactic acid, or salicylic acid preparations to topical retinoids and tazarotene.6,7 These preparations may aggravate associated erythema, limiting their value.
Associations of Keratosis Pilaris
Clinical ichthyosis vulgaris (see Chapter 49) is associated with KP8; in one series KP was found in 74.3% of patients (Fig. 87-1).2 Other conditions in which KP is more prevalent or more prominent are atopic disorders, hypothyroidism, Cushing syndrome, insulin dependent diabetes, obesity or high body mass index, and Down syndrome.9 Follicular keratosis, which may simulate KP, can occur in several nutritional deficiencies, although vitamin A deficiency is most commonly cited (see Chapter 130).10