KIF21A and congenital fibrosis of the extraocular muscles: Congenital fibrosis of the extraocular muscles (CFEOM) affects cranial nerves 3 and 4 and is caused by autosomal dominant missense variants in KIF21A, TUBB3, TUBB2B or TUBA1A or autosomal recessive variants in PHOX2A (9, 10, 12, 86, 87).