Objective:

To describe a rare pediatric presentation of monocular vision loss. 

Background:

Fibrous dysplasia is a condition characterized by the replacement of normal bone tissue with fibrous tissue. Individuals with fibrous dysplasia should be assessed for McCune-Albright syndrome (MAS), which is characterized by peripheral precocious puberty, irregular café-au-lait skin pigmentation, and fibrous dysplasia of bone. 

Design/Methods:

Not applicable.

Results:

A 10-year-old female presented with a 2-month history of painless right monocular vision loss, found to have impaired right visual acuity (20/800) associated with relative afferent pupillary defect and decreased color vision. Head imaging revealed fibrous dysplasia of the skull base with high-grade stenosis of the right optic canal resulting in nerve compression and secondary atrophy; mild to moderate stenosis of the left optic canal without associated nerve entrapment; and mild stenosis of the right paraclinoid internal carotid artery. Further history and examination revealed precocious puberty (onset at nine years of age), tall stature (> 99%), and notable Coast of Maine-shaped hypopigmentation of the left posterior leg (present at birth), all consistent with MAS. Additional laboratory and radiologic evaluations were notable for vitamin D deficiency but otherwise unremarkable, without evidence of polyostotic disease. GNAS testing on blood was within normal limits. Surgical decompression of the right optic nerve was decided against, given her extensive retinal nerve fiber layer thinning and associated poor prognostic recovery and increased risk of additional vision loss.

Conclusions:

Advanced skull base fibrous dysplasia with optic neuropathy secondary to MAS is a rare, atypical, and easily misdiagnosed presentation of monocular vision loss that may mimic more common neurologic disorders such as optic neuritis. Earlier recognition is imperative to improving outcomes, as surgical intervention may not be warranted if the diagnosis is delayed.