Complex strabismus in a patient with KBG syndrome with 16q24.3 microdeletion

KBG syndrome is characterized by intellectual disability, and craniofacial and skeletal abnormalities. We report the case of a 5-year-old boy with KBG syndrome with 16q24.3 microdeletion who showed complex strabismus. Left esotropia and ptosis was first noticed by parents at 18 months of age. He also showed submucosal cleft palate, velopharyngeal insufficiency, prominent eyebrows, short fifth fingers, and fetal finger pad. Marginal reflex distances were +4 mm in the right eye and +1.5 mm in the left eye. He had 18^Δ of left esotropia, and 12^Δ of left hypotropia, which increased with head tilt to the right. Ductions and versions showed bilateral upgaze limitation, more on the right eye, and mild limitation of downgaze on adduction in both eyes. Anti-acetylcholine receptor antibody test, ice test, thyroid function test and the repetitive nerve stimulation test were all negative. Magnetic resonance imaging revealed normal orbital structures, including the bony orbit, oculomotor, trochlear, and abducens nerves, and extraocular muscles in both eyes.