Atopic Dermatitis Differential Diagnoses

Updated: Nov 15, 2017
  • Author: Brian S Kim, MD, MTR, FAAD; Chief Editor: William D James, MD  more...
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DDx

Diagnostic Considerations

Atopic dermatitis (AD) is indistinguishable from other causes of dermatitis. In infancy, the most common difficulty is distinguishing it from seborrheic dermatitis (SD). This entity is not seen with the same frequency as a decade ago. Both AD and SD are associated with cradle cap (a retention hyperkeratosis) found on the vertex of the scalp, which is greasy and yellow in individuals with SD and dry and crusted in individuals with AD. Other areas of involvement in SD are the intertriginous areas and diaper area; erythema and a greasy scale can be seen over the eyebrows and the sides of the nose. In AD, xerosis of the skin and pruritus occur, which are not usually features of SD. Both conditions should be distinguished from psoriasis.

Scabies manifests in infancy or childhood as a pruritic eruption. Other members of the family are usually itchy, and the primary sites of involvement are moist, warm areas. The eruption is polymorphic with a dermatitis, nodules, urticaria, and 6-10 burrows. Pustules on the hands and feet are almost diagnostic of scabies in infancy. Facial involvement is rare, and xerosis does not occur.

Allergic contact dermatitis from nickel in infants and children is sometimes difficult to distinguish from AD. A central area of dermatitis on the chest from nickel snaps in undershirts or around the umbilicus from snaps in jeans is helpful for making the diagnosis, although a dermatitic eruption may occur as an id reaction in other areas, particularly the antecubital fossae. Xerosis and facial involvement are absent. AD usually starts earlier than contact dermatitis.

Infants with a severe itch and generalized dermatitis in the setting of recurrent infections should be investigated for evidence of an immunodeficiency. Failure to thrive and repeated infections help distinguish the eruption from AD. In Wiskott-Aldrich syndrome, bleeding may be prominent with the dermatitis, because of the associated thrombocytopenia. A population-based cohort study by Schmitt J et al. suggested a possible link to the development of mental health issues in patients who experienced infant eczema and concurrent sleeping problems. [42]

In older children, mycosis fungoides (a form of T-cell lymphoma) often presents with hypopigmented patches associated with a dermatitis. This entity is being recognized with increased frequency as physicians become more aware of the disease, and it is sometimes difficult to distinguish between the 2 entities.

Tinea corporis usually manifests as a single lesion, but inappropriate treatment with steroids may cause a widespread dermatitis. Facial involvement, the presence of xerosis, the age of appearance, and an early onset (in AD) help distinguish between the two conditions.

One report describes localized varicella lesions developing in preexisting infectious or inflammatory dermatitis; no clear evidence of full-blown chickenpox was seen. The authors suggest viral testing may be needed if vesicular or ulcerative lesions develop within a preexisting dermatitis. [43]

Differential Diagnoses