Dry and scaly skin

Dry skin (xerosis) is reduced water content and impaired lipid barrier of the stratum corneum, producing roughness, scale and itch.

Mechanisms. Reduced stratum corneum hydration (normally 10 to 20% water), loss of ceramides, cholesterol and free fatty acids, reduced natural moisturising factor from filaggrin breakdown, and impaired desquamation (steroid sulphatase deficiency in X linked ichthyosis).

Classification by cause

• Environmental and constitutional xerosis: low humidity, heating, frequent washing, hot water, soaps, ageing.
• Inflammatory: atopic dermatitis, asteatotic eczema, contact dermatitis, psoriasis, seborrhoeic dermatitis, pityriasis rubra pilaris.
• Inherited ichthyosis: ichthyosis vulgaris (filaggrin mutation, common), X linked recessive ichthyosis, lamellar and congenital ichthyosiform erythroderma, epidermolytic ichthyosis, Netherton syndrome.
• Acquired ichthyosis: lymphoma (especially Hodgkin), solid cancers, sarcoidosis, HIV infection, hypothyroidism, chronic kidney disease, leprosy, malabsorption, drugs.
• Nutritional: zinc deficiency, essential fatty acid deficiency, vitamin A deficiency (phrynoderma), niacin deficiency (pellagra), protein energy malnutrition.
• Infective: tinea, scabies, crusted scabies.
• Drug induced: retinoids, diuretics, statins, lithium, hydroxycarbamide, EGFR and BRAF inhibitors, antiandrogens, and cimetidine.

Distribution clues. Shins, extensor limbs and flanks are favoured in older adults. Flexural sparing with scaling over extensor surfaces and fine white scale suggests ichthyosis vulgaris. Dark polygonal scale over the neck and trunk suggests X linked ichthyosis. Perioral and acral dermatitis with diarrhoea suggests zinc deficiency.

Temporal pattern. Winter predominance suggests simple xerosis. Onset in infancy or childhood suggests ichthyosis or atopy. New generalised scale in an adult needs a systemic search.

History

• Age at onset, family history (ichthyosis, atopy), seasonal pattern, itch, fissuring, bleeding and sleep disturbance.
• Bathing habits (frequency, water temperature, soap, bubble bath, antiseptic washes), emollient use, central heating, occupational wet work and chemical exposure.
• Drugs started in the previous 2 to 12 weeks.
• Weight loss, diet, malabsorption, alcohol use, diarrhoea, bariatric surgery, parenteral nutrition.
• Systemic symptoms: fatigue, cold intolerance (hypothyroidism), night sweats, fever, lymph node swelling (lymphoma), cough (sarcoidosis), polyuria (diabetes), renal and liver disease, HIV risk.
• Atopic history: asthma, hay fever and eczema.
• At birth: collodion membrane, harlequin appearance, prolonged scaling.

Examination

• Distribution, scale colour and size (fine, white, polygonal, plate like or dark), skin texture, fissures, excoriation, erythema, lichenification and crusting.
• Palm and sole thickening, keratosis pilaris, hair and nails, eyelid ectropion.
• Signs of infection: weeping, yellow crusts, painful fissures, vesicles with punched out erosions.
• Nutritional signs: glossitis, angular cheilitis, periorificial dermatitis, hair thinning.
• Signs of systemic disease: goitre, bradycardia, delayed reflex relaxation, lymphadenopathy, hepatosplenomegaly, pallor, jaundice, oedema.
• Burrows and scale in the web spaces.

Red flags

• Generalised scale with erythema over most of the body surface (erythroderma).
• Neonate with a tight shiny membrane, ectropion, eclabium, feeding difficulty or respiratory difficulty (collodion baby, risk of dehydration, hypothermia and sepsis).
• New acquired ichthyosis with lymphadenopathy, weight loss, night sweats or itch.
• Infection of fissured skin with fever, spreading erythema or eczema herpeticum.
• Perioral and acral dermatitis with diarrhoea and hair loss (zinc deficiency, including acrodermatitis enteropathica).
• Scale with failure to thrive, recurrent infection or a hair shaft defect (Netherton syndrome).
• Scale with focal palmoplantar keratoderma and positive family history of oesophageal cancer.

Special groups

• Infants and children: ichthyosis vulgaris appears after 3 months of age and worsens in early childhood. X linked recessive ichthyosis affects boys and may be associated with cryptorchidism and corneal opacities in adult life.
• Pregnancy: use emollients and mild topical corticosteroids. Avoid oral retinoids (teratogenic) and large area salicylic acid.
• Older adults: xerosis is near universal, asteatotic eczema is common, and sedating antihistamines increase falls.
• Kidney impairment: xerosis and itch are frequent in advanced disease and on dialysis.
• Region specific: kwashiorkor and marasmus, zinc and vitamin A deficiency, HIV associated dry skin, and tinea imbricata.

Simple and environmental

• Constitutional xerosis.
• Winter xerosis.
• Xerosis from overwashing and irritant exposure.
• Senile xerosis.

Inflammatory dermatoses

• Atopic dermatitis.
• Asteatotic eczema (eczema craquelé).
• Allergic and irritant contact dermatitis.
• Nummular eczema.
• Psoriasis.
• Seborrhoeic dermatitis.
• Pityriasis rubra pilaris.
• Lichen planus.
• Pityriasis rosea.

Inherited

• Ichthyosis vulgaris.
• X linked recessive ichthyosis.
• Lamellar ichthyosis and congenital ichthyosiform erythroderma.
• Epidermolytic ichthyosis.
• Netherton syndrome.
• Keratosis pilaris.
• Palmoplantar keratoderma.

Acquired ichthyosis and systemic

• Hodgkin lymphoma and non Hodgkin lymphoma.
• Other malignancy (breast, lung, ovarian, multiple myeloma).
• Sarcoidosis.
• HIV infection.
• Hypothyroidism.
• Chronic kidney disease.
• Diabetes mellitus.
• Malabsorption and coeliac disease.
• Chronic liver disease.
• Dermatomyositis.
• Leprosy.

Nutritional and drug induced

• Zinc deficiency and acrodermatitis enteropathica.
• Essential fatty acid deficiency.
• Vitamin A deficiency.
• Pellagra.
• Kwashiorkor and marasmus.
• Drug induced xerosis and ichthyosis (retinoids, diuretics, statins, EGFR inhibitors, lithium, hydroxycarbamide).

Infective and infestation

• Tinea corporis and tinea pedis (moccasin type).
• Scabies and crusted scabies.
• Pityriasis versicolor.
• Tinea imbricata.

Step 1. Decide whether this is simple xerosis. Mild, seasonal, symmetrical xerosis in an older adult with no rash or systemic features needs no tests.

Step 2. Scrapings. Potassium hydroxide microscopy and fungal culture of scale if there is a scaly plaque with an active edge, unilateral hand or foot scaling, or no response to emollients. Skin scraping for mites when itch is nocturnal or there are burrows.

Step 3. First line tests when scale is generalised, acquired as an adult or persistent

• Full blood count with differential, ESR or CRP, urea, creatinine, eGFR, electrolytes, liver tests, albumin, glucose or HbA1c.
• TSH.
• Ferritin and vitamin B12.
• Plasma zinc, taken fasting in the morning because albumin and acute illness lower it; under 10 micromol/L suggests deficiency.
• HIV test.
• LDH when lymphoma is suspected.
• Chest radiograph for hilar adenopathy or mass.

Step 4. Targeted tests

• Serum vitamin A (retinol under 0.7 micromol/L indicates deficiency) and niacin status when diet suggests deficiency.
• Tissue transglutaminase IgA with total IgA.
• CT of chest, abdomen and pelvis and lymph node biopsy for acquired ichthyosis with constitutional symptoms or lymphadenopathy.
• Serum angiotensin converting enzyme and chest imaging for sarcoidosis, with biopsy.
• Skin biopsy (4 mm punch) when the diagnosis is uncertain: ichthyosis vulgaris shows a reduced or absent granular layer, epidermolytic ichthyosis shows hyperkeratosis with vacuolisation.
• Genetic testing (FLG, STS, TGM1 and others) and steroid sulphatase activity or cytogenetics for deletion of the STS gene in suspected X linked ichthyosis; SPINK5 gene analysis in Netherton syndrome.
• Hair shaft microscopy in suspected Netherton syndrome (bamboo hair).
• Patch testing in suspected contact dermatitis.

Limits. Plasma zinc is a poor marker of tissue zinc, and a response to supplementation supports the diagnosis when the level is borderline. Skin biopsy of asteatotic eczema is nonspecific. Acquired ichthyosis may precede the diagnosis of lymphoma by months to years, so repeat evaluation when symptoms evolve.

Immediate. Collodion baby, erythroderma, infected fissured skin with fever and eczema herpeticum need urgent admission and specialist care. Eczema herpeticum needs aciclovir 5 to 10 mg/kg intravenously every 8 hours (adjust for creatinine clearance; maintain hydration).

Emollients and bathing

• Wash with a soap substitute, in lukewarm water, for a maximum of 5 to 10 minutes once daily. Avoid bubble baths, antiseptic washes, abrasive cloths and perfumed products.
• Apply a thick emollient (ointment base for severe dryness, cream for mild) within 3 minutes of bathing and at least twice daily. Use 250 to 500 g weekly for generalised dry skin in an adult. Apply in the direction of hair growth to reduce folliculitis.
• Warn that emollient soaked clothing and bedding is a fire hazard, especially for paraffin based products near naked flames and with smoking.
• Humidify rooms when heating is on; cotton clothing; avoid wool next to the skin.

Topical agents

• Urea 5 to 10% cream twice daily for xerosis and ichthyosis. Urea 20 to 40% for thick palmoplantar scale. Avoid in infants under 1 year and in broken, inflamed skin.
• Lactic acid 5% twice daily, or salicylic acid 2 to 5% in a emollient base on limited areas (not under occlusion, avoid in children under 12 years, pregnancy, extensive areas and kidney impairment because of salicylate absorption).
• Propylene glycol 40 to 60% in water under occlusion overnight for thick scale in ichthyosis (irritation is common).
• Asteatotic eczema or inflammatory dermatitis: mometasone furoate 0.1% ointment once daily for 1 to 2 weeks, then twice weekly as maintenance. Hydrocortisone 1% on the face and flexures. Maximum 50 g weekly of clobetasol propionate 0.05%.

Cause directed

• Tinea: terbinafine 1% cream once or twice daily for 1 to 2 weeks, or clotrimazole 1% cream 2 to 3 times daily for 2 to 4 weeks, continued for 1 to 2 weeks after clearing. Oral terbinafine 250 mg daily for 2 weeks if extensive (125 mg daily if creatinine clearance is under 50 mL/min; not in pregnancy or active liver disease).
• Scabies: permethrin 5% cream to the whole body from the neck down, left on for 8 to 12 hours and repeated after 7 days, with simultaneous treatment of contacts. Ivermectin 200 micrograms/kg orally with food, repeated after 7 days (not for children under 15 kg or pregnancy).
• Secondary bacterial infection: flucloxacillin 500 mg orally 4 times daily for 5 to 7 days (clarithromycin 250 to 500 mg twice daily if penicillin allergic).
• Hypothyroidism: levothyroxine 1.6 micrograms/kg orally once daily on an empty stomach (25 to 50 micrograms daily in older adults and in cardiac disease), titrated every 6 to 8 weeks to a normal TSH.
• Zinc deficiency: elemental zinc 25 to 50 mg orally once daily with food for up to 3 months, with plasma zinc and copper checked at 3 months, since prolonged high dose zinc causes copper deficiency. In acrodermatitis enteropathica use 1 to 3 mg/kg elemental zinc daily, lifelong, under paediatric specialist direction.
• Vitamin A deficiency with eye signs: vitamin A 200,000 IU orally on day 1, day 2 and day 14 for age 12 months or over (100,000 IU at 6 to 11 months; 50,000 IU under 6 months). In women of reproductive age, daily doses over 10,000 IU are avoided because of teratogenicity unless the risk of blindness outweighs it.
• Pellagra: nicotinamide 300 mg orally daily in divided doses for 3 to 4 weeks, with a balanced diet.
• Iron deficiency: ferrous sulphate 200 mg (65 mg elemental iron) orally once daily or on alternate days, continued for 3 months after haemoglobin normalises, with investigation of the cause.
• Chronic kidney disease: emollients, optimisation of dialysis, and itch directed therapy where needed.
• Drug induced: reduce, change or stop the drug when possible. Emollients are the mainstay with retinoids.
• Severe inherited ichthyosis: acitretin 0.5 mg/kg orally daily, usually 10 to 25 mg daily (maximum 50 mg daily), specialist only. Teratogenic: women of reproductive age need reliable contraception during treatment and for 3 years after. Monitor liver tests and lipids every 3 months.
• Acquired ichthyosis: treat the underlying disease.

Monitoring. Review at 2 to 4 weeks for response. Reassess if there is no response to a regular emollient programme within 4 weeks. Check cholesterol, triglycerides and liver tests with retinoids.

Referral and escalation. Dermatology for suspected ichthyosis, erythroderma, refractory eczema and failure of emollient therapy. Neonatology for collodion baby (same day; humidified incubator, emollients, fluid and temperature management). Haematology and oncology for suspected lymphoma. Genetics for inherited ichthyosis, with counselling. Nutrition services for deficiency states.

Admission criteria. Erythroderma, neonates with collodion membrane, infected skin with systemic features, eczema herpeticum, and severe malnutrition.

Disposition. Most patients are managed in primary care. Safety net advice: return for fever, spreading redness, painful blisters, yellow crusting, new lumps in the neck or armpit, weight loss or night sweats.