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INTRODUCTION

This chapter discusses conditions with the common finding of follicular keratosis, defined as orthokeratosis of the follicular ostium and infundibulum. Keratotic plugs protrude from the orifices, producing a rough sensation on palpation of the skin. Keratosis pilaris (KP) is a common, benign form of follicular keratosis; less common variants are associated with follicular inflammation, atrophy, scarring, alopecia, and in rare cases noncutaneous abnormalities. Trichodysplasia spinulosa (TS), a recently described, virally induced follicular dysplasia with similar findings, is also reviewed.

KERATOSIS PILARIS

AT-A-GLANCE

  • Common condition of keratotic follicular plugging with variable erythema.

  • Mainly involves the cheeks, extensor arms, and thighs.

  • Usually improves gradually over years.

  • Nonspecific histology of hyperkeratosis distending the follicular orifice.

  • Variable response to emollients and keratolytics.

  • Variants:

    • Keratosis pilaris rubra: erythema extends beyond perifollicular skin.

    • Erythromelanosis follicularis faciei et colli: erythema and hyperpigmentation.

KP is a common condition characterized by keratotic follicular papules with varying degrees of surrounding erythema. It is common in children and can improve by late adolescence but is often persistent.1 Studies of healthy school-aged children suggest a prevalence of 1% to 34%.2-7 The prevalence is higher in populations with associated conditions.

CLINICAL FEATURES

The primary lesions of KP are small (typically 1-mm), keratotic, follicular papules with varying degrees of perifollicular erythema. Expression ranges from a subtle, incidental finding to conspicuous and aesthetically displeasing, often because of striking erythema. Affected areas include the lateral cheeks, extensor aspects of the upper arms (Fig. 49-1), thighs, and buttocks, and it rarely may be more extensive, extending to the distal limbs and the trunk. Whereas in younger children, the face and arms are mainly involved, the extensor arms and legs are favored in adolescents and adults.

Figure 49-1

Keratosis pilaris in a characteristic distribution on the upper outer arm in a child.

KP is likely accentuated by environmental factors such as ambient humidity. Many with KP experience improvement during the summer as opposed to the winter months or after moving from arid to more humid climates.

Keratosis pilaris rubra (KPR, also called keratosis follicularis rubra) is a variant of KP in which erythema is markedly noticeable, extending beyond the perifollicular skin.8 Findings are usually limited to the cheeks (Fig. 49-2), forehead, and neck. Erythromelanosis follicularis faciei et colli (EFFC) is a similar and likely related condition characterized by hyperpigmentation in addition to erythema and follicular papules.9 It involves the preauricular and maxillary areas, usually in a symmetric distribution, with spread in some cases to the temples and sides of the neck (the suffix “colli” refers to the neck) and trunk. EFFC is seen primarily in adolescents and young adults, most commonly in males. The hyperpigmentation noted in EFFC may be related to intrinsic ...

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