Adult-onset Atopic Dermatitis in a Patch Test Population

Background: Epidemiological studies about atopic dermatitis (AD) almost exclusively relate to childhood disease with little mention of adult-onset disease. In clinical practice, however, patients who have AD and in whom the onset of disease occurs in adult life are sometimes seen.

Objective: Because the subjects with a chronic and recalcitrant eczema are frequently patch tested, the aim of this study was to evaluate the prevalence of adult-onset AD in a patch test population and the differences existing between the early- and adult-onset subsets.

Methods: This retrospective analysis was performed on 502 adults (458 males, 44 females) affected by eczematous dermatitis, consecutively examined in the Department of Dermatology of the Italian Navy Hospital in Taranto. In this department, all the eczematous subjects are routinely submitted to the following tests: standard series (GIRDCA or SIDAPA with integrative haptens), prick test with environmental aeroallergens and common food allergens and dosage of total serum IgE. If it is required, additional series of patch tests are also applied. Many patients are also submitted to the atopy patch test (APT) with whole bodies of house dust mites at a concentration of 20%. In the AD patients, diagnosed according to the criteria of Hanifin and Rajka, the ages of onset were subdivided into the following categories: infancy (0-3 years); childhood (4-11 years); adolescence (> or =12 years). We arbitrarily also used the age of 18 years as the cut-off mark to allocate the patients to the adult-onset group (AOG) and defined as early-onset group (EOG) the cases encompassed in the aforesaid categories (i.e. onset < or =17 years).

Results: 8.8% of all eczemas were adult-onset ADs. 28 (5.6% of all eczemas) adult-onset ADs were 'sole' ADs, while 22 cases (3.2% of all eczemas) were adult-onset ADs in which a contact sensitization was detected. The mean SCORAD indexes, according to the age-of-onset groups, decreased when the age of onset increased. No statistical difference was detected between the EOG and AOG with regard to true contact sensitization, clinically relevant or non-relevant contact sensitization, prevalence of 'pure' AD and 'mixed' AD, and outcome of the APT. The hands were the most frequently affected site in the AOG.

Conclusion: A small but significant number of patch-test-negative eczematous cases could be adult-onset ADs and, in this instance, the other two allergological tests (i.e. prick tests and dosage of total serum IgE) and an accurate evaluation according to stated clinical criteria should be performed. However, other studies on large series of patients are required to confirm our observation.