Dr. Rashmi Sarkar, MD, FAMS, Director Professor Department of Dermatology, Lady Hardinge Medical College and Associated Hospitals, New Delhi, India
Introduction
Atopic Dermatitis (AD) is the most common chronic inflammatory skin disease. The U.S. prevalence of AD was reported to be 11.3–12.7% and 6.9 –7.6% in children and in adults, respectively. The epidermis plays an important role as physical and functional barrier, and skin barrier defects are the most significant pathologic findings in AD skin. Filaggrin (FLG), transglutaminases, keratins, and intercellular proteins are key proteins responsible for epidermal function. Defects in these proteins facilitate allergen and microbial penetration into the skin. Skin barrier dysfunction has been considered to be the first step in the development of atopic march as well as AD. However, it is also now evident that immune dysregulation, including the activation of type 2 immune responses, results in impairment of the epidermal barrier. Recently, new insights into the pathophysiology of the development of AD focused on an important role of abnormalities in epidermal lipid layer as well as neuroimmune interactions and microbial dysbiosis. These factors have been used to develop novel therapeutic and preventative strategies of AD.
Prevalence in Children
Although AD can appear at any time during an individual's life, about 60% of cases are thought to present during the first year, and 60%-74% of cases in children resolve before the age of 16, with the rest persisting into adulthood. However, this supposed rate of clearance is probably around 53% owing to relapses over the course of adolescence and early adulthood. It is worth noting that that a fair percentage of people with childhood. AD experience recurrence when they enter the workforce. Most cases take the form of hand eczema, but some are more extensive.
AD in adults: The course of AD can be continuous for many years but can also show a relapsing-remitting pattern. Early studies had suggested that the disease clears in > 50% of affected children, with just the more severe cases persisting into adulthood. But more recent cross-sectional studies showed that the proportion of patients with persistent or adult-onset disease or with relapses after long asymptomatic intervals is much higher than previously thought. One in four adults with AD report adult-onset disease, which appears to be associated with a different disease phenotype compared with childhood-onset AD and recovery, the microbiota composition reverts to the pre-flare composition.