ABSTRACT
OBJECTIVE: To quantify the relative contribution of factors other than cystic fibrosis transmembrane conductance regulator genotype and environment on the acquisition of Pseudomonas aeruginosa (Pa) by patients with cystic fibrosis. STUDY DESIGN: Lung infection with Pa and mucoid Pa was assessed using a co-twin study design of 44 monozygous (MZ) and 17 dizygous (DZ) twin pairs. Two definitions were used to establish infection: first positive culture and persistent positive culture. Genetic contribution to infection (ie, heritability) was estimated based on concordance analysis, logistic regression, and age at onset of infection through comparison of intraclass correlation coefficients. RESULTS: Concordance for persistent Pa infection was higher in MZ (0.83; 25 of 30 pairs) than DZ twins (0.45; 5 of 11 pairs), generating a heritability of 0.76. Logistic regression adjusted for age corroborated genetic control of persistent Pa infection. The correlation for age at persistent Pa infection was higher in MZ twins (0.589; 95% CI, 0.222-0.704) than in DZ twins (0.162; 95% CI, -0.352 to 0.607), generating a heritability of 0.85. CONCLUSION: Genetic modifiers play a significant role in the establishment and timing of persistent Pa infection in individuals with cystic fibrosis.
Subject(s)
Cystic Fibrosis/genetics , Diseases in Twins/genetics , Genes, Modifier/genetics , Pseudomonas Infections/genetics , Pseudomonas aeruginosa , Respiratory Tract Infections/genetics , Adolescent , Child , Child, Preschool , Cystic Fibrosis/microbiology , Cystic Fibrosis Transmembrane Conductance Regulator/genetics , Epistasis, Genetic , Female , Humans , Male , Pseudomonas Infections/complications , Respiratory Tract Infections/complications , Twins, Dizygotic , Twins, MonozygoticABSTRACT
OBJECTIVE: To assess the relative contributions of environmental and genetic factors to variation in cystic fibrosis (CF) lung disease. STUDY DESIGN: Genetic and environmental contributions were quantified by use of intrapair correlations and differences in CF-specific forced expiratory volume in 1 second measures from 134 monozygous twins and 272 dizygous twins and siblings while in different living environments (ie, living with parents vs living alone), as well as by use of intraindividual differences in pulmonary function from a separate group of 80 siblings. RESULTS: Pulmonary function among monozygous twins was more similar than among dizygous twin and sibling pairs, regardless of living environment, affirming the role of genetic modifiers in CF pulmonary function. Regression modeling revealed that genetic factors account for 50% of pulmonary function variation, unique environmental or stochastic factors (36%), and shared environmental factors (14%; P < .0001). The intraindividual analysis produced similar estimates for the contributions of the unique and shared environment. The shared environment effects appeared primarily because of living with a sibling with CF (P = .003), rather than factors within the parental household (P = .310). CONCLUSIONS: Genetic and environmental factors contribute equally to pulmonary function variation in CF. Environmental effects are dominated by unique and stochastic effects rather than common exposures.
Subject(s)
Cystic Fibrosis/etiology , Cystic Fibrosis/physiopathology , Lung/physiopathology , Adolescent , Adult , Child , Cystic Fibrosis/genetics , Environment , Female , Genetic Predisposition to Disease , Humans , Male , Young AdultABSTRACT
Serum interleukin (IL)-8 levels were measured in 50 patients with ataxia telangiectasia (A-T) and 22 without A-T. In a cross-sectional study, the geometric mean of IL-8 level was significantly higher in the patients with A-T (P <.0001). Elevated serum IL-8 levels in patients with A-T suggest that systemic inflammation may contribute to the disease phenotype.