FOXC1 and Hearing impairment: FOXC1 was the only shared relevant HI-gene in the individuals with hearing impairment in our cohorts (32/44), and the only participant without a FOXC1 deletion did not exhibit hearing impairment (Additional file 2: Figure S2), supporting the hypothesis that haploinsufficiency of FOXC1 is related to the development of hearing impairment in 6p25 deletions.