Atopic Dermatitis: Etiology and Pathogenesis
Etiology and Pathogenesis
Few clinicians have difficulty in identifying the patient with so-called typical AD. Recognizing AD in an infant with a very itchy, usually extensive, recurrent eczematous rash, whose family has had eczema, asthma or hay fever, is easy for most clinicians. However, the combinations and permutations generated by polygenic factors, modified by the varied individual phenotypic exposures endows each patient with an individual atopic fingerprint (profile) and results in a spectrum of clinical signs and symptoms.
Despite the ease physicians have in making the diagnosis of typical cases of AD, a consensus regarding specific diagnostic criteria still evades us, in part because of semantics and in part because of specialty-oriented bias. A clinically useful set of criteria for the diagnosis of AD includes the following: (1) atopy; (2) pruritus; (3) eczema; and (4) altered vascular reactivity. Any attempts to fine-tune these diagnostic features instigates intellectual dissension.
Each criterium is presented individually as part of the clinical manifestations of AD, below. Each feature's immunologic and physiologic implications is then discussed in order to better understand its occurrence and management.