Atopic dermatitis (AD) is a chronic, pruritic inflammatory skin condition that typically affects the face (cheeks), neck, arms, and legs but usually spares the groin and axillary regions. AD usually starts in early infancy but also affects some adults. AD is often associated with elevated levels of immunoglobulin E (IgE). That it is the first disease to present in a series of allergic diseases – including food allergy, asthma, and allergic rhinitis, in order – and has given rise to the “atopic march” theory, which suggests that AD is part of a progression that may lead to subsequent allergic disease at other epithelial barrier surfaces.
.
1. Essential features of AD are pruritus and eczema
The diagnosis of AD is primarily observational. It is made on the basis of patient and family history, pattern of lesions, morphology, and clinical signs. No genetic features or biomarkers are specific enough to reliably aid in diagnosis or severity assessment. Many individual findings are used to diagnose AD, as summarized by the American Academy of Dermatology based on essential, important, associated, and exclusionary features:
- Essential features (must be present for diagnosis) are pruritus and eczema (acute, subacute, or chronic) with typical morphology and age-specific patterns and chronic or relapsing history.
- Important features (usually seen in AD and support the diagnosis) are early age of onset, atopy (personal/family history, IgE reactivity), and xerosis.
- Associated features (nonspecific but suggestive) are atypical vascular response (e.g., delayed blanch response); keratosis pilaris (and some others); ocular/periorbital changes; other regional findings (e.g., perioral changes); and perifollicular accentuation, lichenification, or prurigo lesions.
- Exclusionary conditions (must be excluded to make the AD diagnosis) are scabies, seborrheic dermatitis, contact dermatitis, ichthyoses, cutaneous T-cell lymphoma, psoriasis, photosensitivity dermatoses, immune deficiency diseases, and erythroderma due to other causes.
AD should be differentiated from other red, scaly skin conditions. It is often difficult to separate AD from seborrheic dermatitis in infancy, and the two conditions may overlap in this age group. Particularly if the condition is not responding to therapy, the diagnosis of AD should be re-reviewed and other disorders considered, including more serious nutritional, metabolic, and immunologic conditions in children and cutaneous T-cell lymphoma in adults. Allergic contact dermatitis may be both an alternative diagnosis to AD and an exacerbator of AD in some individuals.
2. Associated comorbidities of AD may exacerbate the condition and lead to other atopic disorders
Reported comorbidities of AD include other atopic or allergic conditions, autoimmune diseases, infections, metabolic conditions, mental health disorders, and cardiovascular disease. Certain aspects of AD, such as chronic pruritus, psychosocial distress, and inflammation, can lead to anxiety, depression, and suicidality. AD is associated with and may predispose to higher risk for other atopic disorders, including asthma, hay fever, food allergy, and eosinophilic esophagitis.
Persons with AD also appear to be at higher risk for infectious diseases. The prevalence of cutaneous and systemic infections in patients with AD is significantly higher than those without AD. Infectious complications can include skin and soft-tissue infections, bacteremia, eczema herpeticum, osteomyelitis, endocarditis, and septic arthritis.