The serine proteases kallikrein-related peptidase (KLK) 5 and KLK7 cleave cell adhesion molecules in the epidermis. Aberrant epidermal serine protease activity is thought to play an important role in the pathogenesis of atopic dermatitis (AD). We collected the stratum corneum (SC) from healthy individuals (n = 46) and AD patients (n = 63) by tape stripping and then measuring the trypsin- and chymotrypsin-like serine protease activity. We also analyzed the p.D386N and p.E420K of SPINK5 variants and loss-of-function mutations of FLG in the AD patients. The serine protease activity in the SC was increased not only in AD lesions but also in non-lesions of AD patients. We found, generally, that there was a positive correlation between the serine protease activity in the SC and the total serum immunoglobulin E (IgE) levels, serum thymus and activation-regulated chemokine (TARC) levels, and peripheral blood eosinophil counts. Moreover, the p.D386N or p.E420K in SPINK5 and FLG mutations were not significantly associated with the SC’s serine protease activity. Epidermal serine protease activity was increased even in non-lesions of AD patients. Such activity was found to correlate with a number of biomarkers of AD. Further investigations of serine proteases might provide new treatments and prophylaxis for AD.

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Many sources suggest that most individuals develop eczema within the first few years of life, experience episodic symptoms throughout childhood, and improve by adolescence. However, newer population-based estimates suggest the prevalence of adult eczema may be similar to childhood disease. The objective of this study was to determine whether the prevalence of eczema declines after childhood. The protocol was registered on PROSPERO prior to the start date. PubMed and Embase were searched and screening and data extraction were performed independently and in duplicate. Population-based cohort studies following the same patients at 3 or more distinct time points with at least one assessment over the age of 12 years old were included. The search yielded 2080 records, and 7 studies with 13,515 study patients met inclusion criteria. Prevalence was measured at 3-6 separate time points in each study, ranging from age 3 months to 26 years old. The annual period prevalence varied from 6% to 34%. The primary outcome was the weighted overall risk difference, defined as the percentage decrease in prevalence after age 12. This figure was 1%, and not significantly different from zero (95% confidence interval-2% to 5%). Similar results were obtained from sensitivity analyses using various age cutoffs. Few studies included measures of disease severity on reported repeated measures of disease activity among individuals. In summary, the prevalence of eczema in longitudinal birth cohort studies is similar in childhood and early adulthood suggesting that eczema should no longer be conceptualized as primarily a childhood disease. Future research should examine predictors of persistent eczema into adulthood.

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