Atopic dermatitis

What it is

Atopic dermatitis (eczema) is a chronic, pruritic, inflammatory skin disease with a wide range of severity. It occurs in around 15-20% of children and is becoming more common.

• Onset is between 3-6 months, and it typically presents before 6 months
• 90% of children are diagnosed by age 5 years
• It clears in around 50% of children by 5 years of age and in 75% by 10 years of age
• About 30% persist into adulthood

Causes and risk

It is multifactorial:

• Genetic predisposition
• Skin barrier dysfunction
• Immune dysregulation
• Environment

It sits within atopy, so a personal and family history of asthma and allergic rhinitis is part of it. Trigger factors, irritants, scratching and hot water all worsen it, so the first treatment is to identify and avoid them. Between six months and two years of age, wheezing, eczema or atopic dermatitis and food intolerance together suggest allergy.

How it presents

Pruritus is the primary symptom: an unpleasant sensation that provokes the desire to scratch. Scratching then leads to the secondary lesions, which are scales, vesiculation, crusts, fissures and lichenification. A typical description is lichenified erythematous papules and plaques with overlying scale, fissuring and crustation. Distribution is symmetric and varies with age:

• Infants: scalp, face and extensor surfaces; the face and trunk are often affected
• Younger children: often the extensor surfaces
• Older children and adults: the flexural areas of neck, elbows, wrists, knees and ankles, and the creases of the face and neck

Eczema of the nipple is pruritic, erythematous, scaly, lichenified patches or plaques, commonly bilateral and extending beyond the areola, typically associated with other signs of atopy. Unlike Paget's disease it has no associated lump and responds to steroid cream.