MuSK and GQ1b Diplopia Masquerading as Heavy Eye Syndrome

Heavy eye syndrome (HES) is an acquired esotropia disorder coincident with myopia often presenting with diplopia. MRI findings may show hypertrophic extra-ocular muscles and surgical intervention can be curative. The GQ1b autoantibody is implicated in a spectrum of ophthalmologic and systemic disorders commonly associated with Miller Fisher Syndrome, and may present with ophthalmoparesis, areflexia, gait ataxia or any combination thereof. MuSK positive Myasthenia Gravis is a rarer form of the disease and is typified by a more aggressive course with early and frequent crises. Here is presented a case of a young woman who presented with episodic horizontal diplopia initially diagnosed and treated as HES later found to be related to systemic MuSK/GQ1b antibody disease.