One of the most common dermatologic conditions encountered in medical practice, keratosis pilaris (KP) affects 30% to 50% of the population. KP is an autosomal dominant disorder; the lesions are caused by an inherited overabundance of keratin around follicular orifices, which often precludes the ability of the hair to exit the follicle. The hairs keep growing, but curl up inside the keratotic papule. Fortunately, aside from mild irritation, KP is essentially asymptomatic.
It has a broad range of presentations, from mild to severe. Some children present with a few barely palpable keratotic papules limited to the bilateral triceps, while others have thousands of papules and large patches of prominent follicles that also involve extensor surfaces of hair-bearing skin. Another version of KP, rubra faceii, is distinguished by very red cheeks with keratotic follicular papules; the unwary provider may suspect acne, but that condition presents with comedones and/or a combination of papules, pustules, or cysts confined to sebaceous (oily) areas. The differential also includes Darier disease (keratosis follicularis), but this has a completely different distribution.
KP is often seen in conjunction with atopic stigmata such as eczema, seasonal allergies, xerosis, asthma, and urticaria. It is believed by some to be a marker for atopy.
Treatment is unsatisfactory in terms of a cure, though most patients see their disease lessen over time. Emollients (heavy moisturizers) containing salicylic acid, glycolic acid, ammonium lactate, or retinoic acid can minimize the height of the papules and smooth the skin, but they do not provide a long-term solution.
TAKE-HOME LEARNING POINTS
- Keratosis pilaris (KP) is an extremely common autosomal dominant condition that affects 30% to 50% of children.
- It manifests very early in life with tiny, hyperkeratotic, follicular papules in a characteristic distribution.
- The bilateral posterior triceps, deltoids, anterior thighs, buttocks, and face are typically affected, while glabrous skin is spared.
- Treatment is difficult; KP responds to emollients and keratolytics containing salicylic acid, glycolic acid, ammonium lactate, and retinoic acid—but any relief will be temporary.