Clinical Sciences/Health Conditions
Alexander Cristian, MD, MD
Resident Physician
University of Miami
Miami, Florida, United States
Nicole L. Pontee, MD
Assistant Professor of Clinical Physical Medicine & Rehabilitation (PM&R)
University of Miami
Miami, Florida, United States
Seronegative myasthenia gravis (SNMG) misdiagnosed as functional neurologic disorder (FND)
Case Description:
A 36-year-old woman with sickle cell trait presented with six months of fluctuating generalized weakness, ptosis, dyspnea, headaches, and intermittent numbness. Prior hospitalizations emphasized psychosocial stressors—including miscarriage, divorce, and job loss—to support a diagnosis of functional neurologic disorder, despite earlier evidence of positive modulating antibodies and mild improvement on pyridostigmine and prednisone. These medications were discontinued before transfer to inpatient rehabilitation. On admission, she demonstrated restricted horizontal gaze, fatigable proximal weakness, and diminished reflexes. Over several days she developed worsening dysphagia requiring NG-tube placement, followed by rapid respiratory decline, ICU transfer, intubation, and pneumonia. ICU electrodiagnostics with repetitive nerve stimulation revealed a decremental response, and a pyridostigmine trial produced rapid clinical improvement, confirming seronegative myasthenia gravis.
Discussions: This case illustrates the diagnostic challenge of SNMG, particularly when early antibody testing and neurophysiology are inconclusive. Psychosocial stressors contributed to premature attribution of her fluctuating weakness, diplopia, ptosis, and dysphagia to FND, resulting in discontinuation of medications that had previously improved symptoms. In the rehabilitation setting, continuous functional assessment revealed progressive fatigability, nocturnal worsening, and declining bulbar function inconsistent with FND. This prompted repeat electrodiagnostic testing, ultimately confirming neuromuscular junction dysfunction. The case highlights how physiatrists’ longitudinal observations and attention to functional patterns can uncover evolving organic pathology overlooked in acute care.
Conclusions:
Rehabilitation physicians play a critical role in identifying when presumed functional symptoms deviate from expected trajectories. Serial assessments, collaborative evaluation with neurology, and timely repeat testing are essential in avoiding delays in diagnosing SNMG. Early recognition and reinstatement of targeted therapy can prevent respiratory failure, reduce complications, and improve functional recovery, underscoring the diagnostic value of the rehabilitation environment.
