Objective:

Not applicable 

Background:

Extraocular movements are typically preserved in motor neuron disease, at least in the early course and can be a helpful differentiator from myasthenia gravis. Exceedingly rare cases of concomitant myasthenia gravis with motor neuron disease were described.

Design/Methods:

Not applicable

Results:

A 54-year-old man presented with progressive shortness of breath over 9-months and bilateral hand weakness over 2-months and was treated with a single round of intra-venous immunoglobulin (IVIG) elsewhere prior to his transfer to our facility. Initial neurological examination revealed respiratory muscle usage, fasciculations, and bilateral intrinsic muscle weakness without hyperreflexia. Of importance, no extraocular movement impairment was noted at the time. A provisional diagnosis of progressive muscular atrophy was made based on the electrodiagnostic testing pending neuroimaging. But a positive acetylcholine receptor binding antibody (AchRB-ab) was noted. Two weeks later at his re-admission, he complained of double vision and noted to have asymmetric ocular abduction paresis, along with worsening respiratory failure necessitating intubation. Repeat electromyography confirmed previous findings, while paraneoplastic/autoimmune-antibodies, spinal fluid analysis, MRI brain and pan-spine were unremarkable. Ocular abduction paresis improved post plasma-exchange but continued needing long-term ventilatory support at three-week follow-up. It should be noted that his acetylcholine receptor antibodies were negative prior to his IVIG and importantly on repeat testing (sent to two independent commercial labs) prior to initiated plasma-exchange.

Conclusions:

Initially, we entertained the idea of a false-positive AchRB-ab result due to the inability to replicate it. However, the presence of ocular symptoms, coupled with extra-ocular movement impairment that responded to plasma-exchange, led us to suspect symptomatic myasthenia gravis caused by passive antibody transfer from IVIG. While passive antibody transfer post-IVIG has been reported for other antibodies, it has not been described for AchRB-ab.