Bilateral Synergistic Convergence Associated with Homozygous ROB03 Mutation (p.Pro771Leu)

Objective: To document the phenotype and determine the genotype of a child with synergistic convergence. Design: Interventional case report. Participants: Patient and nuclear family (7 members total). Methods: Ophthalmologic, neurologic, and radiologic examination of the proband; venous blood sampling for candidate gene testing of the proband; venous blood sampling for confirmatory testing in other family members. Main Outcome Measures: Clinical and radiologic observations in proband and candidate gene results. Results: The proband, a 9-year-old girl, substituted convergence for horizontal gaze (synergistic convergence) since birth. She also had conjugate pendular nystagmus, asynchronous blinking, and high myopia. No family member had ophthalmologic or medical symptoms. Neuroradiologic imaging revealed hindbrain dysplasia and modest scoliosis. Sequencing of ROB03, the gene associated with horizontal gaze palsy and progressive scoliosis, revealed a novel missense mutation (p.Pro771Leu) that altered an evolutionarily conserved amino acid. Screening the family for this mutation confirmed that both parents were carriers and identified 2 sisters as carriers and 2 brothers as noncarriers. Conclusions: This is the second reported patient with synergistic convergence and the first associated with a documented pathologic genotype. Unlike the previously reported case (which occurred in the setting of the cranial dysinnervation disorder congenital fibrosis of the extraocular muscles), our patient presumably has a supranuclear cause. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.