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The diagnosis of pediatric and adult atopic dermatitis is based on clinical presentation and history, but with no reliable biomarker to distinguish it from other erythematous and eczematous conditions, such as seborrheic dermatitis, scabies, contact dermatitis, and psoriasis.

Atopic dermatitis, which is synonymous with atopic eczema or eczema, is characterized by pruritus, erythema, edema, xerosis, erosions, excoriations, oozing, crusting plaques, and lichenification. These clinical findings differ, depending on the patient's age and the chronicity of lesions.

Highly Variable Course

The course of atopic dermatitis is highly variable. In some patients, it waxes and wanes in a relapsing, remitting pattern punctuated by disease flares. At other times, the course is chronic and persistent. In about 80% of patients, the disease is associated with elevated serum immunoglobulin (Ig)E serum levels, and frequently, a personal or family history of allergic rhinitis, asthma, or food allergies.

The American Academy of Dermatology (AAD) estimates that about 60% of atopic dermatitis cases develop in infancy, between the ages of 3 and 6 months, with 90% of cases diagnosed by 5 years. Although pediatric atopic dermatitis usually resolves by adulthood, 10-30% of cases do not, and an increasing number of adults are being diagnosed with persistent and new-onset disease.

Clinical Diversity

The clinical diversity of atopic dermatitis is vast, said Raj Chovatiya, MD, PhD, director of the Center for Eczema and Itch of Northwestern University Feinberg School of Medicine in Chicago. "Essentially, atopic dermatitis is far more heterogeneous than historically believed. It can present with a variety of morphologic and topographic patterns, at varying degrees of severity, and accompanied by different comorbidities and impacts on quality of life."

It is becoming increasingly clear that adult atopic dermatitis is probably more common than previously thought, Chovatiya told MedPage Today. "To further complicate matters, the clinical presentation of disease may not always fit the 'classic' criteria."

"Atopic dermatitis is primarily considered a disease of childhood, so in adults, I do not consider it eczema until proven otherwise," said Cameron Rokhsar, MD, of Mount Sinai Hospital in New York City, in an interview.

Impact on Quality of Life

In active atopic dermatitis, the intense pruritus and rash can be debilitating, and the impact on quality of life profound, even in "mild" disease (mild in the sense of limited extent of affected skin). Comorbid depression, anxiety, and sleep disturbance frequently occur in patients with moderate to severe disease, along with other comorbidities, including possible cardiovascular and skeletal effects.

"Pruritus is a hallmark of the condition that is responsible for much of the disease burden borne by patients and their families," the AAD states in its for the diagnosis and assessment of atopic dermatitis. These guidelines, which were issued in 2013, still stand, said Lawrence Eichenfield, MD, professor of dermatology and pediatrics, and vice-chair of the Department of Dermatology at UC San Diego School of Medicine, who led the expert working group that produced the document. Updated AAD guidelines on topical and systemic therapy and pediatric atopic dermatitis are expected later this year, he told MedPage Today.

Essential Diagnostic Features

To establish a diagnosis of atopic dermatitis in infants, children, and adults, several essential features must be present. These include pruritus and acute, subacute, or chronic eczema with a chronic or relapsing history, as well as typical morphology and age-specific patterns. The latter refer to facial, neck, and extensor involvement in infants and children, and current or previous flexural lesions in patients of any age with sparing of the groin and axillary regions. Other features supportive of a diagnosis of atopic dermatitis include early age of onset; atopic, personal, and/or family history; IgE reactivity; and xerosis.

Conditions that mimic atopic dermatitis must be excluded. "In very early life, a variety of immunologic disorders or genetic diseases may need to be considered," said Eichenfield, who is also chief of Pediatric and Adolescent Dermatology at Rady Children's Hospital-San Diego. "In adults with new-onset atopic dermatitis, cutaneous lymphoma should be considered in the differential diagnosis," he said.

Scabies, seborrheic dermatitis, irritant or allergic contact dermatitis, ichthyosis, psoriasis, photosensitivity dermatoses, immune deficiency diseases, and erythroderma of other causes also must be excluded prior to a diagnosis of atopic dermatitis.

"On occasion, skin biopsy specimens or other tests (such as serum immunoglobulin E, potassium hydroxide preparation, patch testing, and/or genetic testing) may be helpful to rule out other or associated skin conditions," the guidelines note. Sometimes, another skin condition, such as allergic contact dermatitis, can be both an alternative diagnosis and/or an exacerbator of atopic dermatitis.

The physical appearance of atopic dermatitis also varies based on skin pigmentation. In patients with light skin pigmentation, for example, erythema may appear more red, while in those with darker pigmentation, it may appear more violaceous. The skin lesions characteristic of atopic dermatitis also differ between patients from different racial groups globally, sometimes with adverse consequences.

Disparities

"Recent studies support disparities in atopic dermatitis diagnosis, healthcare utilization, treatment, and overall patient burden, particularly in non-white racial groups," said Chovatiya.

In the U.S., "there is unequal care delivery in certain populations, including Black patients, who may present later and with more severe disease," added Eichenfield. "We are working harder to -- and need to -- get affected patients and families to access specialty care more easily and regularly, and to educate our communities on the incredible changes in the care of atopic dermatitis."

Atopic dermatitis prevalence is higher in Black Americans compared with white Americans (19.3% vs 16.1%, respectively). In patients with brown, dark brown, or black skin, erythema associated with atopic dermatitis may be difficult to see, noted Bridget Kaufman and Andrew Alexis in a on the National Eczema Association website. Other features such as edema, dryness/scaling, or pruritus and oozing may help confirm the diagnosis, they said.

Black Americans with atopic dermatitis are more likely to develop papular eczema on the torso, arms, and legs, with follicular accentuation resembling goosebumps. Blacks are also at greater risk of prurigo nodules resulting from extensive scratching, and experience a higher rate of lichenification and pigmentary changes following resolution of eczema compared with their white counterparts, Kaufman and Alexis said.

"Future studies should aim to develop personalized medicine approaches for atopic dermatitis patients across different races and in different parts of the world," suggested authors of a review in .

Although contributory food allergies are seen in about 35% of children with moderate-to-severe atopic dermatitis, the clinical significance of specific IgE antibodies and serum-specific IgE levels is still unclear, noted Sandeep Kapur and colleagues in . "In general, the younger the patient and the more severe the atopic dermatitis, the more likely it is that specific food allergens may exacerbate the disease," they wrote.

A positive skin prick test or serum-specific IgE test to a particular allergen does not prove clinical hypersensitivity or causation, those authors emphasized. What's more, random testing or screening for food allergens is not recommended as it can lead to inappropriate dietary restrictions. "The positive predictive value of screening panels of food allergens in such cases is as low as 2%," Kapur and co-authors wrote, adding that food allergies appear to play "little, if any role" in adult atopic dermatitis.

On the other hand, the team said, the use of skin prick tests to establish sensitization to aeroallergens such as house dust mites, animal dander, pollen, and molds may be useful, particularly if the history suggests a causative role in worsening atopic dermatitis.

Read Part 1 of this series: Atopic Dermatitis: Reasons for Optimism