8q12 microduplication including CHD7: clinical report on a new patient with Duane retraction syndrome type 3

A novel multiple congenital anomalies syndrome has been recently identified in four patients carrying a 8q12 microduplication sharing the smallest region of overlap (SRO, size 1.6 Mb) including five genes CA8, ASPH, RAB2B, CLVS1 and CDH7. The phenotype is mainly characterized by neurodevelopmental delay, heart defects, facial features and Type 1 Duane anomaly. Increasing dosage of CDH7 was proposed to be responsible for the recurrent pattern of MCA.

High resolution array-CGH analysis identified a 4.2 Mb de novo interstitial duplication of the 8q12.1-q12.3 chromosome region in a boy with developmental delay, dysmorphic features, type 3 Duane anomaly. This duplication includes several genes and spans the SRO.

The present case represents a further patient with an interstitial duplication of chromosome 8q12 and several shared clinical features. Although more cases are needed to delineate the full-blown phenotype of 8q12 duplication syndrome, published data and present observations suggest that it results in a clinically recognizable phenotype. The presence of Duane anomaly in four out of five described patients with a 8q12 duplication definitely rules against the possibility of its being a chance finding unrelated to the imbalance and points toward a pathogenic role. Gene content analysis of the duplicated region and review of the literature suggest that gain-of-dosage of the CHD7 gene may be a good candidate for the main clinical features of the syndrome.