logo Disorders of Keratinisation

Scaly skin diseases

Disorders of keratinisation

Objectives

  • Describe features of lichen planus, lichen sclerosus, ichthyosis and keratosis pilaris.

Key points

  • Lichenoid histology refers to liquefaction degeneration of basal layer, dermal infiltration of inflammatory cells hugging the basal layer, colloid bodies and dermal melanin.
  • Idiopathic lichen planus is associated with liver diseases.
  • Signs of lichen planus are polygonal papules and plaques on ventral wrists, forearms and legs.
  • Mucosal lichen planus may result in white lacy marks or painful erosions.
  • Causes of lichenoid drug eruption include thiazides, anti-malarials, gold and ACE inhibitors.
  • Lichen sclerosus is a common cause of vulval itching and soreness in postmenopausal women.
  • Signs of lichen sclerosus are white plaques, haemorrhage and ulceration.
  • Ichthyosis is characterised by excessively dry and scaly skin.
  • Autosomal dominant ichthyosis vulgaris causes generalised dryness most prominent on upper arms.
  • Autosomal recessive lamellar ichthyosis may result in collodion baby and extensive plate-like scales.
  • X-linked recessive ichthyosis is associated with deficiency of steroid sulfatase.
  • Bullous ichthyosiform erythroderma cause blistering and scaling erythematous skin.
  • Bullous ichthyosiform erythroderma is due to autosomal dominant mutation in keratin 1 and 10.
  • Acquired ichthyosis is associated with cachexia and kava consumption.
  • The main treatment for ichthyosis is emollients containing urea and/or lactic acid.
  • Keratosis pilaris is common on the outer aspect of upper arms and anterior thighs.
  • Follicular plugs of keratin may be accompanied by erythema especially on arms and face.
  • Pityriasis rubra pilaris is a group of rare skin disorders resulting in erythematous scaly plaques with follicular prominence.
  • Darier’s disease is an uncommon inherited disorder presenting as scaly papules.

Lichenoid diseases

Many skin diseases include the term “lichen”, which is thought to originate from a resemblance to the lichen that is found on trees.

Lichen simplex is a type of eczema and was discussed earlier. There are several other uncommon “lichen” conditions that will not be considered in this course.

Lichenoid histology refers to liquefaction degeneration of basal layer, dermal infiltration of inflammatory cells hugging the basal layer, colloid bodies (degenerating keratinocytes) and dermal melanin.

Low power view of lichenoid histology

Close-up showing liquefaction degeneration


Idiopathic lichen planus has the following features:

The ventral wrist is a typical site for lichen planus

The shins is a common site for lichen planus

Hypertrophic lichen planus

Lacy-pattern lichen planus in buccal mucosa

Nail dystrophy due to lichen planus

Close-up of polygonal papules and plaques. Note white streaks (Wickham’s striae)


Treatment of lichen planus may include:

Erosive lichen planus affects the oral and/or genital mucosa. It may result in very painful ulceration and scarring.

Erosive lichen planus of buccal mucosa

Erosive lichen planus of tongue

Erosive lichen planus of vulva and vagina


Lichenoid drug eruption has similar histology, and sometimes clinical appearance. More often there is a diffuse eruption of mildly irritable flat dry patches on trunk and limbs. Common causes include thiazides, anti-malarials, gold and ACE inhibitors.

Lichen sclerosus is a common cause of vulval itching and soreness in menopausal women. It less commonly affects women and children of all ages, and may present as asymptomatic white plaques on other sites. It is thought to have an autoimmune origin. On the vulva, perineum and perianal mucosa, it causes white plaques, atrophy, sclerosis (scarring), haemorrhage, blistering and ulceration. It predisposes to squamous cell carcinoma.

Axillary lichen sclerosus

Penile lichen sclerosus (previously called balanitis xerotica obliterans)

Vulval lichen sclerosus in pre-pubertal child

Extensive vulval, perineal and perianal lichen sclerosus

Hypertrophic lichen sclerosis

Perianal squamous cell carcinoma arising in lichen sclerosus


Patients with lichen sclerosus should be under the care of a dermatologist. Ultrapotent topical steroids are generally successful but should be used with caution because of potential adverse effects. Topical calcineurin inhibitors offer a promising alternative.

Ichthyosis

Ichthyosis refers to a group of disorders of keratinisation characterised by excessively dry and scaly skin. Genetic analysis is identifying the protein abnormality responsible in specific subtypes. The most common are:

Autosomal dominant ichthyosis vulgaris
The most common type (1:250)
Histology: absent granular layer
Most severe in childhood but may persist in adult life
Predisposes to atopic dermatitis
Generalised dryness most prominent on upper arms
May have hyperlinear palms
Autosomal recessive lamellar ichthyosis
Collodion baby (neonate encased in a membrane)
Extensive scaling on erythematous base
Mutation in gene coding for glutaminase (and other mutations)
X-linked recessive ichthyosis
Deficiency of steroid sulphatase in affected child and carrier mother
Large scales on trunk and limbs
Flexures may be spared
Bullous ichthyosiform erythroderma
Blistering and erythematous skin in infants
Prominent scaling on erythematous base in adults
Autosomal dominant mutation in keratin 1 and 10

Acquired ichthyosis is the dry skin associated with cachexia and certain forms of cancer and lymphoma. It is also characteristic in heavy consumers of kava.

Ichthyosis vulgaris

X-linked ichthyosis

Hyperlinear palms in ichthyosis vulgaris

Bullous ichthyosiform erythroderma in infant

Bullous ichthyosiform erythroderma in older child

Acquired ichthyosis in kava drinker


Treatment of ichthyosis requires regular application of emollients containing urea and/or lactic acid and the use of soap substitutes when bathing. Oral retinoids may be prescribed for severe cases.

Keratosis pilaris

Keratosis pilaris affects up to 50% of adolescents and may present from neonate to middle-age.

Erythema of upper arm due to prominent keratosis pilaris

Keratosis pilaris faciei

Close up of follicular plugging


Keratosis pilaris rarely clears with treatment. Try urea-containing emollients to soften the affected areas and topical retinoids to encourage normal follicular keratinisation.

Pityriasis rubra pilaris

A group of rare skin disorders resulting in localised erythematous scaly plaques rather like psoriasis. However there is less scaling and prominent follicular involvement. Keratoderma of palms and soles is usual. Some types result in erythroderma.

Juvenile pityriasis rubra pilaris

Palmar keratoderma

Follicular papules


Darier’s disease

An uncommon inherited disorder with disordered keratinisation, resulting in characteristic greasy reddish papules in scalp and trunk, palmar pitting and nail changes.

Darier’s disease mid-back

Submammary Darier’s disease