Infantile esotropia with cross-fixation, inability to abduct, and underlying horizontal gaze palsy with progressive scoliosis

Children affected by infantile esotropia can cross-fixate to see object to the contralateral side with the adducted eye; when doing so they need not abduct the eye ipsilateral to the object and thus can appear to have abduction defects. Less commonly, an esotropic child is truly unable to abduct and cross-fixates to allow side gaze. We report the case of a 10-month-old girl with cross-fixation and inability to abduct who was genetically proven to have horizontal gaze palsy with progressive scoliosis (recessive ROBO3 mutations). Clinical assessment of her elder brother, previously diagnosed with bilateral type 3 Duane retraction syndrome, revealed that he was actually affected by the same disease. We highlight this rare ocular motility disorder as part of the differential diagnosis of early childhood esotropia with cross-fixation and inability to abduct and how examination of an affected sibling can facilitate proper diagnosis of genetic eye disease.