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

Abstract and Introduction

Abstract

Keratosis pilaris is a common skin disorder comprising less common variants and rare subtypes, including keratosis pilaris rubra, erythromelanosis follicularis faciei et colli, and the spectrum of keratosis pilaris atrophicans. Data, and critical analysis of existing data, are lacking, so the etiologies, pathogeneses, disease associations, and treatments of these clinical entities are poorly understood. The present article aims to fill this knowledge gap by reviewing literature in the PubMed, EMBASE, and CINAHL databases and providing a comprehensive, analytical summary of the clinical characteristics and pathophysiology of keratosis pilaris and its subtypes through the lens of disease associations, genetics, and pharmacologic etiologies. Histopathologic, genomic, and epidemiologic evidence points to keratosis pilaris as a primary disorder of the pilosebaceous unit as a result of inherited mutations or acquired disruptions in various biomolecular pathways. Recent data highlight aberrant Ras signaling as an important contributor to the pathophysiology of keratosis pilaris and its subtypes. We also evaluate data on treatments for keratosis pilaris and its subtypes, including topical, systemic, and energy-based therapies. The effectiveness of various types of lasers in treating keratosis pilaris and its subtypes deserves wider recognition.

Introduction

Keratosis pilaris (KP), colloquially known as "chicken skin," is a common skin disorder characterized by keratotic papules in a folliculocentric distribution. Management of KP is often sub-optimal, partly because of the fragmented nature of the medical literature relating to the condition; the last review article on the subject was published 10 years ago.[1] The high prevalence of KP contrasts with the relative lack of attention paid to it; KP is often dismissed as a cosmetic issue. Despite the lack of attention, new data on the condition, its syndromic associations, medications that can cause or exacerbate the condition, and therapeutic options are available. Our intent is to critically review this literature and provide a comprehensive update. We also hope to direct further attention to KP from those who develop therapeutic agents and devices. To accomplish this, we performed a literature review of KP using the PubMed, EMBASE, and CINAHL medical databases using the search term keratosis pilaris. Only peer-reviewed articles available in English were included.

Epidemiology

KP is the most common follicular disorder in children.[2,3] The pediatric epidemiology of KP has been explored by several groups (Table 1), but there appear to be large fluctuations in the reported prevalence rates among and even within countries or ethnicities, ranging from 0.75 to 34.4%.[4–15] In addition, a cross-sectional study of 12,657 Korean male military conscripts aged 19 years reported higher rates of KP in the subjects than did results from hospital-based studies.[16] The prevalence of KP was 11.9% (178/1502) in a cross-sectional study of 1502 German adults.[17] In a prospective study of 1107 Spanish and 1267 immigrant patients aged < 60 years, KP was more prevalent in the immigrant population (p = 0.04).[18] KP also occurs more frequently in individuals with skin scaling and dryness,[7,19] regardless of whether they have a diagnosis of ichthyosis vulgaris (IV) or atopic dermatitis (AD).[20]

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