I have founn a few different papers and sites that talk about approximately 30% of people with Duane syndrome having other issues..."Duane syndrome with associated congenital anomalies. Approximately 30% of individuals with Duane syndrome have other congenital anomalies, particularly of the ear, kidney, heart, upper limbs, and skeleton. These associated anomalies are typically reported in simplex cases, but also occur together with Duane syndrome as familial malformation or genetic syndromes.