Exotropic Duane syndrome with synergistic divergence and no mutations in COL25A1

Typical Duane retraction syndrome, a common form of congenital cranial dysinnervation disorder (CCDD), is rarely due to a monogenic mutation. However, the unusual form of exotropic Duane syndrome with synergistic divergence was recently associated with bi-allelic mutations in the gene COL25A1, raising the possibility that this particular Duane syndrome phenotype could be a monogenic recessive CCDD. To explore this possibility, we tested 4 consecutive unrelated subjects with the diagnosis for COL25A1 mutations. None harbored pathogenic variants, evidence that exotropic Duane syndrome with synergistic divergence is notspecifically caused by mutations in the gene.