Mondo Description Any congenital fibrosis of extraocular muscles in which the cause of the disease is a mutation in the KIF21A gene.

Uniprot Description A congenital ocular motility disorder marked by restrictive ophthalmoplegia affecting extraocular muscles innervated by the oculomotor and/or trochlear nerves. It is clinically characterized by anchoring of the eyes in downward gaze, ptosis, and backward tilt of the head. Patients affected by congenital fibrosis of extraocular muscles type 1 show an absence of the superior division of the oculomotor nerve (cranial nerve III) and corresponding oculomotor subnuclei.