Introduction

Keratosis pilaris (KP) is a common, harmless skin condition that affects 50-80% of all adolescents and 40% of adults worldwide.¹ It is an over-accumulation of keratin in the hair follicles, that causes small, red papules (bumps), known as perifollicular erythema to appear. This gives the skin a “goosebump or “strawberry-like” appearance. These papules are most prevalent on the upper arms, followed by the thighs, then the buttocks.²

There is a strong genetic component to KP, frequently seen in members of the same family. It typically has an autosomal dominant pattern of inheritance, which means that a person has a 50% chance of inheriting the condition if one parent has KP; however, this can vary. KP also varies in its presentation and can be classified into 4 types: Classic KP, KP Rubra, KP Alba and KP Atrophicans.³ Distinguishing between these four types and their features, such as scarring and non-scarring, is crucial to guide management for patients.

Classic Keratosis Pilaris.

The most common form of KP is Classic keratosis pilaris. Classic KP presents symmetrically across the body, with follicular papules that are small, sandpaper-like, and flesh-coloured. These papules are usually asymptomatic but sometimes present with mild dryness or itchiness. They can contain finely coiled, brittle hair, with a slight redness surrounding the hair follicle resulting in a speckled strawberry-like appearance of the skin. Often, these papules appear during childhood or adolescence and fade with age. They are either scattered or grouped around the upper arms, thighs and buttocks.. For approximately 50% of Classic KP patients, papules become more noticeable during the winter. Cold temperatures cause ‘xerosis’ of the skin, where it becomes dry, tight, and flaky due to a lack of moisture and friction from clothing. Classic KP may cause appearance-related distress, especially in children and adolescents.² 

Keratosis Pilaris Rubra

Keratosis pilaris rubra presents with a brighter redness of the papules and a wider distribution over the skin. The most common locations of papules include the upper arms, neck, cheeks, and close to the forehead in some cases. KP rubra typically starts during childhood, and is most prevalent in adults between the ages of 20 and 40. Due to the presentation of KP rubra on the cheeks, it can cause greater concern about appearance, possibly leading to emotional distress or lower self-esteem.³ 

Keratosis Pilaris Alba

In Latin, “Alba” is directly taken from the word “Albus”, meaning “white”. Keratosis pilaris alba is when the papules present as white or skin-coloured without any erythema. This variant tends to occur commonly in children less than one year old. The frequency of keratosis alba declines with increasing age, affecting both males and females equally. In most cases, these are not inflammatory papules and are often seen on the upper arms, thighs, buttocks and sometimes on the face. The key difference is that it will be less red compared to keratosis pilaris rubra.⁴ 

Keratosis Pilaris Atrophicans

Keratosis pilaris atrophicans is a rare and more severe type of keratosis pilaris, which presents as patches of scarred, thinned skin, also known as skin atrophy. In classic KP, abnormal keratinisation of the hair follicle leads to rough follicular papules, whereas in KP atrophicans, the plugging causes inflammation and damage to the skin. There are several subtypes of KP atrophicans: Keratosis pilaris atrophicans falciei (KPAF), Atrophoderma Vermiculatum, and Keratosis follicularis spinulosa decalvans (KFSD).⁵ 

The KPAF subtype affects the outer third of the eyebrows, causing scarring, atrophy, and alopecia. It typically arises during infancy and progresses slowly into childhood, but stabilises after puberty. KPAF can be associated with a variety of genetic diseases, including Noonan Syndrome, Cornelia-de-Lange Syndrome, and other congenital abnormalities.⁶

Atrophoderma Vermiculatum is another subtype of KP alba that mainly affects children. It has a distinct ‘honeycomb’ pattern of scarring and atrophy, focused on the cheeks but may extend towards the ears and forehead. It may also cause facial redness.⁷

KFSD is rare and typically passed on through X-linked inheritance, meaning that the condition is more prevalent in men. KFSD arises in early childhood, affecting the face and scalp. It is a rare type of progressive scarring alopecia of the scalp, and sometimes eyelashes and eyebrows, that initially appears as classic KP. The alopecia may present as patchy and limited, or widespread. Puberty can cause the condition to worsen with stronger crusting, extensive scaling, or eruptions of pustules on the scalp.⁸

Clinical Importance

Keratosis pilaris is a broad umbrella term covering common variants and those that are more rare, including those that can lead to scarring, atrophy and in some cases alopecia. The presentations of most of these variants are typically on the face or scalp, which can cause self-esteem issues.. Differentiating between the types is important in diagnosis and management of the disease. Treatments include emollients, keratolytics, laser treatment, and retinoids, depending on the type. Support for emotional wellbeing, including counselling or talking therapies, may also be necessary.

FAQs

What are the risk factors for keratosis pilaris?

• Family history of keratosis pilaris 
• Dry skin
• Eczema (Atopic dermatitis)
• Ichthyosis vulgaris 

How is keratosis pilaris diagnosed? 

There is no formal test for KP; usually, a healthcare professional can make a diagnosis based on the typical appearances. 

Is there a cure for keratosis pilaris?

There is no cure for keratosis pilaris; however, it may naturally clear with age.

What are keratolytics?

These are creams that help shed and soften the skin by breaking down keratin, the protein that makes up the tough outer layer. These creams are usually applied directly to the affected areas. Common examples of keratolytics agents include: 

• Salicylic acid
• Urea 
• Lactic acid 

What can I do? (Self-care)

Reducing skin dryness may help manage the symptoms of keratosis pilaris. These include general measures and lifestyle advice including:

• Avoiding long hot baths and showers 
• Avoiding over-exfoliation, gentle use of exfoliators only 
• Avoiding fragranced products, which can irritate the skin
• Use of mild soaps or soap substitutes 
• Applying emollients regularly 

Does diet or lifestyle affect keratosis pilaris? 

There is no strong evidence linking diet to KP; however, hydration and a healthy, balanced diet may have some general benefits for the skin. 

Is Keratosis Pilaris contagious?

Keratosis pilaris is not contagious, so you cannot spread it or catch it from an affected patient.

Summary

KP is a harmless and common skin condition that typically affects children and adolescents. KP encompasses several subtypes, some of which result in scarring, atrophy, or alopecia. The four primary subtypes include Classic KP, KP Rubra, KP Alba, and KP atrophicans. These variants can present on the face and scalp, often causing distress related to appearance and self-esteem. Accurately distinguishing between the types is essential for effective diagnosis and management.