Keratosis Pilaris and its Subtypes

Associations, New Molecular and Pharmacologic Etiologies, and Therapeutic Options

Jason F. Wang; Seth J. Orlow

Disclosures

Am J Clin Dermatol. 2018;19(5):733-757. 

In This Article

Conclusion

KP is a very common skin condition in children and adults. It is often dismissed as a cosmetic issue, but this can lead to missed diagnoses of a variety of associated diseases, hereditary syndromes, and adverse events from medications as well as inadequate treatment. Further characterization of these associations will shed much needed light on the pathophysiology of KP and its subtypes, which can lead to a better understanding of how to develop effective therapies. More data on the effectiveness of old and new therapies are necessary to update treatment guidelines. Based on our comprehensive review of the literature, we present the following conclusions:

  • KP is common, but prevalence appears to vary with ethnicity. Genetics appear to play a major role in KP and its subtypes.

  • KP typically presents during childhood; spontaneous improvement during adolescence is common.

  • Diagnosis of KP is usually made clinically, but dermos-copy and biopsy can aid with diagnosis.

  • KPA is a rare, scarring, atrophic subtype of KP potentially due to a mutation in LRP1; KPA comprises a spectrum of clinical entities with variable overlap and pediatric onset that tend to improve during adolescence, including KPAF, AV, KFSD, and—potentially—FSD.

  • EFFC is a rare, pigmented subtype of KP without scarring or atrophy but with pediatric onset and clinical overlap with KPR.

  • KPR and PPPKP are common but underreported variants of KP, while unilateral presentations of KP and its subtypes are rare.

  • Although the pathogenesis of KP has not yet been fully elucidated, many factors, including histopathologic findings, the tendency of KP to improve during adolescence, the association of KP with filaggrin mutations and 18p monosomy, the effects of androgen and insulin dysregulation, and reduced prevalence of KP in patients with acne vulgaris, support KP as a disorder of the sebaceous gland, which in turn disrupts the permeability barrier of the SC and causes aberrant keratinization and hair abnormalities.

  • The association of KP with atopy and IV may stem from a defect in the permeability barrier partially caused by filaggrin mutations. However, given the etiological heterogeneity and high prevalence of both disorders, the presence of KP should not be considered a diagnostic criterion for AD.

  • Changes in androgen and insulin levels that manifest in obesity, diabetes, and pregnancy can directly affect sebocytes and contribute to the pathogenesis of KP.

  • KP is associated with several PCAs, including GLPLS, acne keloidalis, and FFA.

  • Of the syndromes with ID as a cardinal feature, the association of KP and DS is the most evidence-based.

  • Of the RASopathies, KP and KPAF are more common in cardio-facial-cutaneous syndrome than in CS or NS. Because KP is also caused by B-Raf inhibitors, aberrant signaling in the Ras pathway may be crucial to the pathogenesis of KP.

  • KP is associated with several EDs, including PKCAS, HMD, PC, and monilethrix, and hereditary skin appendage disorders, including WH, hypotrichosis, HK, and LT.

  • Medications known to cause KP-like eruptions include cyclosporine, the B-Raf inhibitors dabrafenib and vemurafenib, and the TKIs nilotinib, dasatinib, ponatinib, erlotinib, and sorafenib.

  • Sudden KP-like eruptions warrant a thorough medical evaluation, with special attention to medications.

  • LA, SA, urea, topical retinoids, tacrolimus, Aquaphor, fractional prickle coral calcium, spray-on Nitrosomonas eutropa mist, and chorine dioxide complex cleanser have been shown to be at least partially effective in treating KP.

  • The data on systemic drugs for the treatment of KP and its subtypes are sparse and conflicting.

  • Preliminary data suggest that photopneumatic therapy is effective in treating KP and intense pulsed light is effective in treating KPA.

  • Lasers that are effective in treating KP or its subtypes include PDL, KTPL, alexandrite laser, long-pulsed diode laser, Q-switched Nd:YAG laser, and fractional carbon dioxide laser.

Since KP is so common, it is difficult to distinguish true associations from those that occur by chance, especially with environmental exposures and rare diseases. More studies are necessary to cement disease associations, gain further insight into the pathophysiology of KP, and establish effective treatment guidelines.

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