Heterogeneity of atopic dermatitis defined by the immune response to inhalant and food allergens.

Although atopic dermatitis (AD) is a common disease, its etiopathogenesis is not well known. The diagnosis of AD is based solely on the clinical criteria proposed by Hanifin and Rajka. In order to understand the immunological mechanisms involved in the pathogenesis of AD, we have classified the patients affected by this disease in four groups according to the results of skin prick-tests, specific IgE and patch-tests. This classification is intended to separate and compare the patients affected by AD according to the involvement of immunological type I and/or type IV mechanisms. Our results show that, although all the patients studied are clinically affected by AD, there are four different groups of patients who present an apparently diverse immunopathological mechanism. There is a group that seems to have an IgE mediated mechanism, another group that suggests a cell mediated mechanism, another group which seems to involve both mechanisms, and yet another group that apparently does not show any of the above mentioned mechanisms. In the present article we hypothesize and argue that the imbalance of the immune system is a consequence of the still unknown etiopathogenetic mechanism of AD, but perhaps not the cause of AD.

Searching for psoriasis susceptibility genes in Italy: genome scan and evidence for a new locus on chromosome 1.

Psoriasis is a chronic inflammatory dermatitis, affecting approximately 2% of the population. Major clinical features include red, scaly patches on scalp, elbows, and knees, with or without severe arthritis. Several putative susceptibility loci have been mapped by parametric and non-parametric linkage analysis to chromosome regions 2p, 4q, 6p, 8q, 16q, 17q, and 20p; however, the most significant results and confirmation of linkage are only available for the 17q and 6p chromosome regions at present. In this study, 22 multiplex Italian families were investigated for linkage to 6p and 17q susceptibility regions, using a set of four microsatellites. These analyses failed to detect significant linkage with any of the examined markers. A genome-wide scan was then performed on one of the largest pedigrees, searching for an additional susceptibility locus. This study disclosed a putative linkage to chromosome 1cen-q21 markers. When these microsatellites were analyzed in the remaining families of the sample, a significant linkage was observed using both parametric and non-parametric methods. The highest two-point lod score value was obtained with D1S305 marker (3.75 at 0 = 0.05). Non-parametric analysis at this locus also demonstrated a significant excess of allele sharing (p = 0.0001).

The relationship between allergy, clinical symptoms and bronchial responsiveness in atopic dermatitis.

Atopic Dermatitis (AD) and asthma are closely associated with respect to epidemiology, hereditary factors and occurrence in the same individuals. Bronchial Hyperresponsiveness (BH), the hallmark of asthma, can also be a physiopathological feature of AD, even in the absence of clinical asthma. We studied 78 subjects with AD. A follow-up study was performed in 27 of these. Data on respiratory and dermatologic symptoms were collected by means of a standardized questionnaire. Skin reactivity was evaluated by prick testing, and in 57 subjects BH was assessed with a methacholine test (Mch). Twenty-one subjects had asthma and 36 showed a positive skin reaction. A PC20 FEV1 was measurable in 38 subjects. Males were found more likely to be Mch responders than females (p < 0.05). Mch responders also showed an earlier age at onset of AD than nonresponders (2.1 yrs vs. 6.2, p = 0.03). Determinants of the degree of BH were evaluated by a stepwise multiple regression analysis, taking the log of the slope of the concentration response curve as dependent variable. In the final model we found that the degree of BH was directly related to wheezing (p = 0.0017) and coughing (p = 0.04) and inversely related to lung function (p = 0.0082) and age (p = 0.0008). Neither skin reactivity nor grading of AD were statistically significant. The longitudinal study demonstrated that the courses of AD and BH seem to run parallel only in skin-negative subjects, whereas an increase in BH was observed in skin-positive subjects.