Environmental and Genetic Factors Associated with Congenital Microtia: A Case-Control Study in Jiangsu, China, 2004 to 2007

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Abstract
The objectives of this study were to filter out the environmental and genetic risk factors in microtia patients and to demonstrate the relationship between environmental and inherited factors in congenital microtia. A case-control study was carried out in 121 congenital microtia patients and 152 controls. Epidemiologic data related to environmental exposure were gathered through personal interviews with the target group. Polymerase chain reaction and DNA sequence analysis were performed to analyze the Gsc gene and BMP5 gene mutation in the case and control groups. The logistic regression model was used to analyze environmental and genetic risk factors and their relationships to microtia. The main risk factors were disease during pregnancy (odds ratio, 5.890; 95 percent CI, 2.358 to 14.715), toxicity exposure during pregnancy (odds ratio, 4.764; 95 percent CI, 1.659 to 13.680), and resident area (odds ratio, 5.114; 95 percent CI, 2.086 to 12.535). The synthetic attributable risks amount to 0.7185. As to the Gsc gene, six of these patients had a same-sense mutation C-->T on 197 bp in exon 2; a missense mutation on A-->G 125 bp in exon 3 occurred in two cases; and amino acid changes from glutamic acid to glutamine. A heterozygosity on 196 TTT-->ACA resulting in missense mutation was detected in four patients, causing the amino acid to change from phenylalanine to threonine in BMP5 maternal peptide gene. However, no mutations were detected in the control subjects. The results suggested that both environmental and genetic factors contribute to congenital microtia. The Gsc gene and the BMP5 maternal peptide gene may act as the predisposing genes of microtia. Further research is needed to clarify the relationship between the risk factors and microtia.

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