Keratosis Pilaris

Keratosis pilaris (KP), also known as follicular keratosis or lichen pilaris, is a common autosomal-dominant genetic skin condition characterised by the presence of small, gooseflesh-like bumps, often with varying degrees of reddening or inflammation. These bumps are caused by the overproduction of keratin, a skin protein, which forms plugs within hair follicles. This condition is colloquially referred to as "chicken skin."

Signs and Symptoms

KP results in small, rough bumps on the skin's surface, often the size of a grain of sand. These bumps are typically skin-coloured but may be surrounded by slight pinkness in light-skinned individuals or dark spots in dark-skinned individuals. Although many people with KP do not experience symptoms, the bumps can sometimes be itchy. Scratching may lead to inflammation and redness. KP is a year-round condition but tends to worsen during the colder months when humidity levels drop. The condition might also exacerbate during pregnancy or post-childbirth. Increased sun exposure may mitigate the symptoms, although this is anecdotal.

Pathophysiology

KP occurs due to the body's overproduction of keratin, which surrounds and traps hair follicles in the pores, leading to the formation of hard plugs (hyperkeratinisation). Often, these bumps contain ingrown hairs that have coiled underneath the skin. KP is more common in individuals with atopic diseases such as allergic rhinitis and atopic dermatitis. Some KP subtypes are part of genetically inherited syndromes associated with intellectual disability, neuro-cardio-facial-cutaneous syndromes, RASopathies, ectodermal dysplasias, and certain myopathies.

Diagnosis

Typically, physicians diagnose KP through the visual examination of the skin, without the need for specialised tests. However, dermoscopy can be useful in confirming the diagnosis and assessing treatment response. Family history and the presence of symptoms are also considered. Patients are encouraged to seek medical advice if the condition becomes bothersome and does not improve with over-the-counter treatments.

Differential Diagnosis

Certain medications, such as cyclosporine, BRAF inhibitors, and tyrosine kinase inhibitors, can cause skin eruptions similar to KP.

Classification

KP can be classified into several types, including KP rubra (red, inflamed bumps), KP alba (rough skin with no irritation), KP rubra faceii (reddish rash on the cheeks), KP atrophicans, keratosis follicularis spinulosa decalvans, atrophoderma vermiculatum, KP atrophicans faciei, erythromelanosis follicularis faciei et colli, and papular profuse precocious KP. KP is often seen in conjunction with other dry-skin conditions, such as ichthyosis vulgaris, dry skin, and atopic dermatitis.

Treatment

While KP is medically harmless, individuals often seek treatment due to cosmetic concerns. Topical creams and lotions are the most common treatments. These include moisturisers and keratolytic agents such as urea, lactic acid, glycolic acid, salicylic acid, vitamin D, fish oil, and topical retinoids like tretinoin. Improvement typically takes months, and the condition often recurs. Gentle exfoliation and limiting shower time can also help manage KP. Laser therapies, including fractional carbon dioxide lasers and Nd:YAG laser treatments, have shown effectiveness in some cases, requiring multiple sessions over several months.

Epidemiology

KP affects an estimated 30 to 50% of the adult population and 50 to 80% of adolescents worldwide. It is more common in women and can affect people of all ethnicities. Although it can occur at any age, KP usually appears within the first decade of life and tends to improve before the age of 30, although it can persist longer.

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Self-assessment MCQs (single best answer)

What is another name for Keratosis Pilaris?

What causes the small bumps in Keratosis Pilaris?

Which of the following is NOT a symptom of Keratosis Pilaris?

Which of the following can exacerbate Keratosis Pilaris?

Which diagnostic tool can confirm the diagnosis of Keratosis Pilaris and assess treatment response?

Which subtype of Keratosis Pilaris is characterised by red, inflamed bumps?

Which of the following is a common topical treatment for Keratosis Pilaris?

What percentage of the adult population is affected by Keratosis Pilaris?

At what age does Keratosis Pilaris usually appear?

Which laser therapy has shown effectiveness in treating Keratosis Pilaris?