Scaly skin diseases
Disorders of keratinisation
- Describe features of lichen planus, lichen sclerosus, ichthyosis and keratosis pilaris.
- 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.
Many skin diseases include the term “lichen”, which is thought to originate from a resemblance to the lichen that is found on trees.
- Idiopathic lichen planus
- Erosive lichen planus
- Lichenoid drug eruption
- Lichen sclerosus
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:
- An association with primary biliary cirrhosis, hepatitis-C and perhaps other liver diseases
- Polygonal papules and plaques on ventral wrists, forearms and legs
- Lacy pattern of white marks on buccal mucosa &/or genitals
- Perifollicular erythema and scaling in the scalp resulting in scarring alopecia (lichen planopilaris)
- Variable itching
- Koebnerisation (lichen planus arising in areas of minor skin trauma such as excoriation)
- Nail dystrophy
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:
- Potent topical steroids
- Systemic steroids
- Sometimes, immune suppressive agents or retinoids.
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 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.
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 affects up to 50% of adolescents and may present from neonate to middle-age.
- Common sites are outer aspect of upper arms and anterior thighs
- The rough skin is due to follicular plugs of keratin
- May result in non-pruritic erythema
- Rarely causes loss of the lateral eyebrows (ulerythema oophyrogenes)
- May cause red dry cheeks (keratosis pilaris faciei)
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
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