Clinical features of the extrinsic and intrinsic types of adult-onset atopic dermatitis

BACKGROUND Most study concerning the prevalence and dermatological manifestations of the extrinsic and the intrinsic form of atopic dermatitis (AD) were performed in children and adult AD related to the early-onset AD extending to adult life. Adult-onset AD is a subgroup of AD. Apart from the typical eczematous flexural distribution pattern of AD, this group may also have nontypical morphology and localization. OBJECTIVE The purpose of this study was to compare the clinical and diagnostic features of Thai patients with extrinsic and intrinsic type of adult-onset AD. METHODS We retrospectively studied case records of patients diagnosed as adult-onset AD at the skin allergy clinic, Department of Dermatology, Siriraj Hospital, Mahidol University, Bangkok, Thailand from June, 2006 to May, 2008. The diagnosis of AD was made according to the criteria of Hanifin and Rajka and the severity of AD in each patient were assessed using the eczema area and severity index and the Rajka and Langeland score. RESULTS Fifty six patients were enrolled. Eighty-seven percent of patients were extrinsic AD (eAD). Females predominated in both groups. Patients with eAD more commonly had typical lichenified/exudative eczematous lesions, especially on the antecubital and popliteal areas, when compared with patients with intrinsic AD (iAD). Nummular and follicular lesions were more commonly seen in iAD group than the eAD group. The most common area of involvement in the iAD was non-flexural area, followed by flexural area and extensor area. The severity of both iAD and eAD did not show a significant difference. CONCLUSION The eAD type of adult-onset AD was more common than the iAD type. Patients with eAD frequently had flexural lichenification whereas the iAD group tended to have nonflexural area involvement. The severity of both iAD and eAD did not show a significant difference.