Keratosis Pilaris

Common benign disorder of follicular keratinisation in which keratin plugs block the hair follicle openings. It affects 50 to 80% of adolescents in some series and about 40% of adults, and usually improves after the age of 30.

• Inheritance is autosomal dominant with variable penetrance, and a family history is present in about 50%. Loss-of-function variants in the filaggrin gene (the same defect that underlies ichthyosis vulgaris and atopic dermatitis) are common, so it clusters with atopy and dry skin.
• Associations: atopic dermatitis, ichthyosis vulgaris, obesity, diabetes mellitus, and several genetic syndromes (Noonan, cardiofaciocutaneous, Down). Keratosis pilaris atrophicans (ulerythema ophryogenes, atrophoderma vermiculatum) is a scarring variant of the face.
• It is worse in winter and in dry climates, and improves in humid summer conditions. Pregnancy and puberty can change its course.
• There is no cure, and treatment aims to improve texture and appearance. Treatment is cosmetic and is not medically necessary.

• Multiple, small (1 to 2 mm), follicular, skin coloured to red or brown papules with a keratotic plug, giving a rough "goose flesh" or sandpaper feel. A coiled hair may be trapped in the plug.
• Typical sites: the extensor upper arms (the commonest), anterior thighs, buttocks and cheeks in children. The forearms, trunk and lower legs are less commonly involved. The palms and soles are spared.
• Erythematous variant (keratosis pilaris rubra): surrounding redness, more common on the face and upper arms.
• Variants: keratosis pilaris alba (pale), and hyperpigmented forms in darker skin.
• Itch is mild or absent. Persistent itch suggests coexisting atopic dermatitis.
• Differential diagnosis: folliculitis, acne, lichen spinulosus, phrynoderma (vitamin A and essential fatty acid deficiency), scurvy (perifollicular haemorrhage and corkscrew hairs), pityriasis rubra pilaris, lichen planopilaris, keratosis follicularis (Darier disease), eruptive vellus hair cysts, atopic dermatitis and miliaria.
• Complications: cosmetic distress, post-inflammatory hyperpigmentation from picking, and secondary folliculitis.

• Clinical, based on distribution and morphology. No investigations are required.
• Check for atopy, ichthyosis vulgaris, diabetes and obesity when relevant. Check for dietary deficiency (vitamin A, vitamin C) in malnourished patients, those with malabsorption or those with perifollicular haemorrhage.
• Biopsy is needed only for atypical or scarring forms, and shows a dilated follicle plugged by orthokeratotic keratin.

• Explain that the condition is harmless and chronic, that treatment is cosmetic and suppresses rather than cures, and that improvement takes 6 to 12 weeks of regular use.
• Skin care:
  • Gentle, soap free cleansers, with lukewarm showers of short duration.
  • Avoid scrubbing, loofahs and abrasive scrubs, which cause irritation and pigmentation.
  • Apply a rich emollient twice daily within 3 minutes of bathing, and use humidifiers in dry weather.
• Keratolytic and moisturising agents (first line), applied once or twice daily, tapered to maintenance:
  • Urea 10 to 20% cream or lotion (up to 40% for thick plaques) twice daily.
  • Lactic acid 5 to 12% lotion (ammonium lactate 12%) twice daily.
  • Salicylic acid 2 to 6% lotion or cream once or twice daily. Avoid extensive use over large areas in children, in pregnancy, and in renal impairment, because of systemic absorption (salicylism).
  • Glycolic acid 5 to 10% lotion once daily.
• Topical retinoids for persistent disease, applied at night:
  • Tretinoin 0.025 to 0.05% cream or adapalene 0.1% gel once nightly, building up from alternate nights.
  • Tazarotene 0.05 to 0.1% cream for resistant cases.
  • Expect dryness and irritation, and use sun protection. Avoid in pregnancy and lactation.
• Short course topical corticosteroid for inflamed or red lesions: hydrocortisone 1% or mometasone furoate 0.1% once daily for 1 to 2 weeks, repeated only when needed. Long term use does not improve the texture and causes atrophy.
• Procedural options for troublesome cosmetic disease (the evidence is limited):
  • Pulsed dye laser for redness.
  • Long pulsed alexandrite or diode laser hair reduction for the follicular component.
  • Microdermabrasion and superficial chemical peels (salicylic acid 20 to 30%, glycolic acid 30 to 70%) every 2 to 4 weeks, for 3 to 6 sessions.
  • Oral isotretinoin is not indicated, since the effect is poor and relapse follows stopping.
• Special groups:
  • Children: use emollients, urea 5 to 10% and lactic acid 5%, and avoid strong keratolytics and retinoids.
  • Pregnancy and lactation: use emollients, urea and lactic acid. Avoid retinoids and large area salicylic acid.
  • Darker skin: avoid irritation and aggressive peels because of post-inflammatory pigmentation.
  • Renal impairment: limit salicylic acid to small areas.
• Follow up: review at 8 to 12 weeks. Refer to dermatology for atrophic or scarring variants, features of a genetic syndrome, or failure of treatment where the patient wants procedural therapy.