Diagnostic outcomes of exome gene panel sequencing in patients with unusual syndromic cleft lip/palate phenotypes

Abstract

Orofacial clefting (OFC) is a common craniofacial birth defect that has a prevalence of 1.2 in 1,000 live births. Syndromic OFC in which patients present with additional developmental deficits are identified to have a strong genetic component. We applied exome gene panel sequencing in a cohort of 14 Colombian patients identified at Operation Smile in Bogota, Colombia, with syndromic orofacial clefting phenotypes and additional features initially suggesting Aarskog-Scott syndrome (AAS). Gene panel sequencing failed to identify any causal variants in the FGD1 gene which underlies this condition, but variants in a number of genes suggest alternative clinical diagnoses across five patients (~ 36%). The novel variants identified here maps to developmentally important genes including SRCAP, OFD1, NIPBL, GRIN2A and KMT2D6. Our result demonstrates the extensive heterogeneity underlying OFC and emphasises the need for systematic phenotyping of patients with rare conditions. Gene panel sequencing has the potential to cost-effectively resolve ambiguous clinical diagnoses, but rigorous attention should be paid to gene coverage as our results suggest highly variable read depths across individual gene exons and this may reduce the quality of variant calls at specific locations.