ASTHMA PREVALENCE AND RISK FACTORS Morphological and Molecular Characteristics of "Difficult" Asthma

Background. There are several clinical variants of severe difficult-to-treat asthma: asthma with persistent airflow limitation, brittle asthma, and fatal asthma; but the differences between the pathogenetic mechanisms underlying the disease heterogeneity are unknown. Objectives. The aim was to evaluate the morphological and molecular characteristics of brittle asthma type I and asthma with persistent airflow limitation compared to mild-to-moderate asthma, by the analysis of the cellular structure and gene expression in the bronchial mucosa. Methods. Bronchoscopic evaluation was performed in 42 asthmatic patients: 10 with brittle asthma, 10 with severe asthma with persistent airflow limitation, and 22 with mild-to-moderate asthma. Morphometric and cytological analyses of the bronchial mucosa were performed. The mRNA levels for the ADRB2, HRH1, and CHRM3 genes in the bronchial mucosa were measured by quantitative real-time polymerase chain reaction (PC