Proptosis secondary to bilateral extraocular muscle enlargement in Noonan syndrome with hypertrophic cardiomyopathy: A case report

Purpose To report and investigate proptosis in a young girl with Noonan syndrome. Methods Observational case report. Results A 16-year-old girl affected by Noonan syndrome underwent a complete ophthalmological examination showing bilateral proptosis with hypofunction of lateral rectus and superior oblique muscles. Visual acuity, color discrimination and fundus examination were unremarkable. The orbital MRI showed bilateral proptosis and symmetrical enlargement of extraocular muscles, with bellies thickening and tendon sparing. The young patient also complained restrictive hypertrophic cardiomyopathy. Conclusions Proptosis is an uncommon ocular manifestation of Noonan syndrome and its pathophysiology has never been clarified. The MRI evidence of extraocular muscles enlargement associated with hypertrophic cardiomyopathy, led us to hypothesize a common altered pathway beneath these features, more specifically the MAP kinase pathway, since extraocular and cardiac muscles share a mesenchymal embryological origin.