Keratosis pilaris

 

Salient features

·        Common condition of keratotic follicular plugging with variable perifollicular erythema.

·        Mainly involves the cheeks, extensor arms, and thighs.

·        Usually improves gradually over years.

·        Nonspecific histology of hyperkeratosis distending the follicular orifice.

·        Variable response to emollients and keratolytics.

·        Variants:

o   Keratosis pilaris rubra: erythema extends beyond perifollicular skin.

o   Erythromelanosis follicularis faciei et colli: erythema and hyper pigmentation.

 

 

 

Introduction

 

Keratosis pilaris (KP) is a genetic disorder of keratinization affecting the hair folliclular orifice with varying degree of keratotic follicular plugging, perifollicular erythema and follicular atrophy. It is an extremely common benign condition that manifests as small, rough folliculocentric keratotic papules with variable perifollicular erythema, often described as chicken bumps, chicken skin, or goose-bumps, in characteristic areas of the body, particularly the outer-upper arms and thighs.

 

Because up to half of the population present with the condition to some degree, it can be considered a variant of normal rather than a disease. Overall, keratosis pilaris is self-limited and, again, tends to improve with age in many patients. Some patients have lifelong keratosis pilaris with periods of remissions and exacerbations.

 

 

Epidemiology

 

Incidence and prevalence

 

KP is a very common condition affecting 50-80% of adolescents and approximately 40% of adults worldwide.

 

Age

 

KP often presents in the first decade of life and may worsen around puberty and the problem tends to improve thereafter (especially facial involvement). Adolescents and adults are disturbed by the appearance.

 

Sex

 

Females appear to be more frequently affected than males.

 

 

Pathophysiology

 

Keratosis pilaris (KP) is a disorder of hyperkeratinization of the skin. An excess formation and/or buildup of keratin are thought to cause the abrasive goose-bump texture of the skin.  The individual papules in keratosis pilaris are thought to arise from excessive accumulation of keratin at the follicular orifice and this impedes the hair from emerging that is unable to reach the surface and becomes trapped beneath the keratin debris. The hair can become ingrown and result in an inflammatory response.

 

 

An excess of keratin in the hair follicles forms a hard plug that feels like a bump.

 

 

Pathology

 

Histopathology of keratosis pilaris (KP) lesions shows the triad of epidermal hyperkeratosis, hypergranulosis, and plugging of individual hair follicles.

 

An orthokeratotic keratin plug blocks and dilates the orifice and upper portion of the follicular infundibulum. Horny plugs protrude from the orifices, producing a rough sensation on palpation of the skin. A twisted hair shaft may be trapped within this keratin material, and a mild perivascular lymphocytic infiltrate in the adjacent upper dermis.

 

Genetics

 

KP is inherited as an autosomal dominant trait with variable penetrance. Approximately 30-50% of patients have a positive family history. Keratosis pilaris is more common in siblings and in twins.

 

Environmental factors

 

KP may show seasonal variation. Dry skin conditions seem to exacerbate the disease. Symptoms generally tend to worsen in winter and improve in summer. 

 

Associated diseases

 

KP may affects over 40 % of patients with atopic dermatitis and over 75 % with ichthyosis vulgaris.

 

 

Clinical features

 

KP generally starts in children, most commonly on the extensor surfaces of the upper arms, and can worsen around puberty.

There are very small (1 to 2 mm), skin colored folliculocentric keratotic papules, often with a rim of erythema or (especially on the cheeks) a background of patchy erythema are most commonly distributed on the posterolateral aspect of the upper arms, and anterior and lateral thighs, as well as cheeks but rarely may be more extensive, extending to extensor aspects of the distal limbs and the trunk. The buttocks and the lumbar areas are also frequently affected. These areas acquire a ‘goose‐bump’ appearance and rough texture. Lesions can become pustular with superficial pustules developing in affected follicles, precipitated by rubbing on clothing. Palpation may reveal a fine, sandpaper like texture to the area. In some instances, scratching away the surface of some papules may reveal a small, coiled hair.

Two main patterns exist. In early childhood onset, cheeks and extensor arms are mainly affected and gradual improvement is seen in most cases by adolescence (especially facial involvement). In adolescence onset, extensor arms and thigh are predominantly involved. It usually improves by the mid-20s. However, in both patterns, the condition may be persistent into later adult life.

The keratosis pilaris rubra (KPR) variant features numerous tiny, “grain-like” follicular papules superimposed on intense confluent erythema; often widespread (face & ears > trunk & proximal extremities) and tends to persist after puberty.

 

Treatment

 

KP is principally a cosmetic problem and many people do not know they have it. If it does not bother the patient, treatment is unnecessary. Benefit from topical therapy is often limited and many patients will not persist with it. Occasionally, physicians may prescribe a 7- to 10-day course of a group V, emollient-based topical steroid cream (eg, Locoid Lipocream, Cloderm) to be applied once or twice a day for inflamed, red areas. Once the inflammation has remitted, the residual dry rough papules may be treated with twice-daily application of a keratolytic preparation. Application of 12% ammonium lactate lotion (Lac-Hydrin, AmLactin), urea cream (10% to 40%), or salicylic acid lotion 6% reduces the roughness of the skin. Treatment may need to be continued for many years. Abrasive washing techniques cause further drying.