Congenital fibrosis of extraocular muscles (CFEOM) is a strabismus syndrome characterized by congenital inability to move the eye muscles with or without ptosis (droopy eyelids). It is inherited in an autosomal dominant manner. The CFEOM1/KIF21A gene causes congenital fibrosis of the extraocular muscles (CFEOM). Exons 2, 8, 20, and 21 of KIF21A contain all pathogenic mutations identified to date. The clinical sensitivity of this test has not been determined, but KIF21A mutations are responsible for most familial and simplex cases of congenital fibrosis of the extraocular muscles. This laboratory performs Sanger sequencing of select exons within KIF21A.