Further refinement of the differentially methylated distant lung-specific FOXF1 enhancer in a neonate with alveolar capillary dysplasia.

Heterozygous SNVs or CNV deletions involving the FOXF1 gene, or its distant enhancer, are causative for 80-90% of cases of alveolar capillary dysplasia with misalignment of pulmonary veins. Recently, we proposed bimodal structure and parental functional dimorphism of the lung-specific FOXF1 enhancer, with Unit 1 having higher activity on the paternal chr16 and Unit 2 on the maternal chr16. Here, we describe a novel unusually sized pathogenic de novo copy-number variant deletion involving a portion of the FOXF1 enhancer on maternal chr16 that implies narrowing Unit 2 to an essential ~ 9-kb segment.