Duane syndrome associated with Rubinstein-Taybi syndrome type II.

We report the case of an 8-month-old infant born at 33 weeks' gestation referred to our institution for evaluation of left eye abduction deficit and microcephaly. Ophthalmic examination revealed a left eye abduction deficit with palpebral fissure narrowing on adduction along with palpebral fissure widening on abduction, consistent with Duane syndrome. Genetic testing revealed a pathogenic EP300 mutation confirming Rubinstein-Taybi syndrome type II. The cooccurrence of Duane syndrome and Rubinstein-Taybi syndrome is rare, with only 3 cases in the literature, 2 with genetic confirmation. Potential involvement of the cranial nerves in Rubinstein-Taybi syndrome may explain its cooccurrence with Duane syndrome, which is seemingly more common in EP300-mediated disease.