What You Should Know About Atopic Dermatitis
- Volume 18 - Issue 9 - September 2005
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Atopic dermatitis (AD) has a multiplicity of clinical presentations and many authorities consider it to be a syndrome. It is a chronic inflammatory pruritic skin disease that is often associated with elevated serum IgE levels and a personal or family history of type 1 allergies, allergic rhinitis and asthma. This condition is made up of a group of specific signs and symptoms that characterize the dermatological expression of the atopic diathesis.
Atopic dermatitis predominantly affects infants, children and young adults. Approximately 60 percent of the cases are diagnosed within the first year of life and 90 percent of all cases are diagnosed by the age of 5. Only 10 percent of AD cases are diagnosed over the age of 5 and it is rare for the condition not to be identified before a patient reaches his or her teens. The condition follows a relapsing course and most adults who suffer from AD have had it nearly all of their lives. However, a very small percentage of adults may first develop AD after the age of 18.
Even though there are a few limitations in the clinical diagnosis of AD, the world literature continues to note AD as a common condition that is becoming more widespread. Some believe this increase of atopic disease in developed countries can be attributed to reduced microbial exposure in early life. Antiseptic soaps, skin cleansers, antibacterial household sprays, mouthwashes, floor cleaners and a large list of other “hygiene” products may have been the basis for this increasing occurrence of AD.
In spite of the high prevalence of AD, there is still a lack of generalized consensus regarding the diagnosis, treatment and follow up of this condition. Unfortunately, since this problem is called, among other things, pediatric eczema, atopic eczema and atopic dermatitis, the diagnostic criteria and true prevalence of AD will continue to remain inaccurate. The incidence of AD is further complicated by the common pattern of frequent remissions and changeable clinical courses, especially with the milder forms of AD.
A Few Thoughts On The Etiology And Pathophysiology Of AD
There is no strong consensus on the etiology of AD but the greatest risk factor is a parental history of atopy or isolated eczema. The term atopy is generally and probably simplistically used to describe the clinical presentation of type I hypersensitivity, which one may see among patients with asthma, hay fever, eczema, urticaria and assorted allergies to food and/or wool products.
Maternal atopy conveys a greater risk for offspring having atopic disorders than paternal atopy. Additionally, AD is inversely related to the number of siblings. In other words, the larger the family size, the less likely a child will have AD. As noted earlier, AD and atopy seem to be conditions of the advantaged classes in developed countries with a definite trend toward an increase of AD cases in these industrialized nations over the past few decades.
Other than the genetic etiology, some still consider food and environmental antigens to be factors in the pathogenesis of AD. Atopic dermatitis is usually worse in extremes of climate. Generally, the condition poorly tolerates heat and extreme cold. A dry atmosphere in winter increases dry skin and exacerbates AD. On the other hand, sun exposure improves the eczema but sweating increases the pruritus.
Studies suggest there is an aberration of T helper 2 cells that results in an augmented production of interleukin-4 and increased IgE levels. This excess of interleukin-4 causes decreased interferon gamma levels. Tissue cells react with environmental antigens to produce increased levels of IgE. There are associated increases of serum and cellular histamine release and some believe these increases may be due to mast cell release from antigen-antibody reactions.