To assess the possible correlations between the reported candidate genes (VEGFR3, FOXC2, ITGA9 and ITGB1) and the clinical response in fetuses with severe congenital chylothorax (CC) treated by prenatal OK‐432 pleurodesis.

We studied 12 unrelated fetuses with severe CC, receiving fetal therapy by OK‐432 pleurodesis. Genotyping of the candidate genes and the clinical parameters of these 12 fetuses were investigated. Additional 96 control individuals were enrolled to evaluate the possible polymorphisms at these candidate genes in population.

A recurrent heterozygous missense mutation (c.1210G > A, p.G404S) was identified in the beta‐propeller domain of integrin α₉ (ITGA9), a cell adhesion receptor, in four of the five fetuses who failed to respond to the OK‐432 treatment. Computer modeling of the p.G404S substitution supported the deleterious nature of this mutation. Family analyses in three affected fetuses demonstrated that the heterozygous mutant allele is of parental origin, suggesting an autosomal recessive inheritance of this genetic defect.

To the best of our knowledge, this is the first insight into the possible link between ITGA9 and CC in human fetuses. The identification of pathogenetic mutations and their possible link to the clinical responses of particular treatments may contribute to better pregnancy counseling and management. Copyright © 2008 John Wiley & Sons, Ltd.