Atopic dermatitis

Atopic dermatitis is the most common type of eczema, occurring in approximately 5% of the population. There was approximately 19 million diagnosed cases of moderate atopic dermatitis in 2017 in the Seven Major Markets. Disease onset is most common by five years of age, and UNION estimates that approximately 60% of patients suffering from atopic dermatitis are paediatric patients. Atopic dermatitis is the most common skin disease among children, affecting approximately 15% to 20% of children.

The presence of food sensitisation and allergy earlier in life predict a prognosis of severe atopic dermatitis. Around 50–70% of children with an early onset of atopic dermatitis are sensitised to one or more allergens. These are mainly food allergens (cow's milk, hen's egg and peanuts being the foods most frequently involved) but also house dust mite, pollen and pets. Food allergy is more common in children with atopic dermatitis with an association that ranges from 20% to 80% with most dermatologists pointing to around 30%. The relationship between food allergy and atopic dermatitis is complex and can be viewed from different perspectives. It has been proposed recently that food allergy may not have such an important impact on the initiation of atopic dermatitis. In most cases, rather than being a cause of atopic dermatitis, food allergy would be co-associated with atopic dermatitis or would be an exacerbating factor for atopic dermatitis. Food allergies have indeed clinical manifestations on the skin and in the gastrointestinal and respiratory systems. Cutaneous reactions can be diverse, but only some of them will exacerbate atopic dermatitis, and they usually manifest as a late event. Skin reactions can lead to excessive scratching and indirect exacerbation of pre-existing eczema.

 

Atopic dermatitis is characterised by a defect in the skin barrier, which allows allergens and other irritants to enter the skin, leading to an immune reaction and inflammation. This reaction produces a red, itchy rash, most frequently occurring on the face, arms and legs, and the rash can cover significant areas of the body (see figures below), in some cases half of the body or more. The rash causes significant pruritus (itching), which can lead to damage caused by scratching or rubbing and perpetuating an 'itch-scratch' cycle.

Given most of the patients are paediatric, safety and tolerability of atopic dermatitis treatments is paramount and explains the predominance of topical treatments. Atopic dermatitis imposes a substantial burden on both the patient and, particularly in the case of paediatric patients, the parents and family. Paediatric patients with atopic dermatitis can suffer from sleep disturbances, behavioural problems, irritability, crying, interference with normal childhood activities, and social functioning. Parents and families of paediatric patients with atopic dermatitis can also be impacted by a lack of sleep, emotional distress due to their child's suffering, and added workload caring for the atopic dermatitis patient. Adults with atopic dermatitis also frequently suffer from sleep disturbances, emotional impacts, and impaired social functioning. Adults with atopic dermatitis also appear to be at a significantly increased risk of anxiety, depression, and suicidal ideation compared to the general population.

Biologics and oral treatments are primarily (and almost exclusively) prescribed by dermatologists with little global variation and topical treatments are primarily prescribed by primary care physicians. However, for newly launched topicals such as Eucrisa®, the early adaptors and primary prescribers for the first one to three years after launch will be dermatologists.

 


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