Thymomatous Myasthenia Gravis Pre- and Post- Thymectomy


Clinical Management

Poster Number: Virtual


Shawn Allen, MD, Cedars-Sinai Medical Center, Nasheed I. Jamal, MD, Department of Neurology, David Geffen School of Medicine at UCLA


Myasthenia Gravis (MG) is an autoimmune disorder of the neuromuscular junction leading to fatigable and fluctuating weakness most commonly affecting the extraocular, bulbar, and limb muscles. A thymoma is found in approximately 15% of patients with MG.

OBJECTIVE: To describe the course of myasthenia gravis before and after thymectomy in a patient found to have an incidental thymoma on chest XR


A 68-year-old man, with no significant history, presented for evaluation after a chest XR completed in as part of a new employee medical evaluation found an incidental 4.5-cm anterior mediastinal mass, later
confirmed on chest CT. Upon referral to thoracic surgery, further evaluation revealed positive acetylcholine receptor binding, blocking, and modulating antibodies, but the patient remained asymptomatic. Three months after the chest XR, the patient developed symptoms of diplopia, ptosis, and occasional globus upon swallowing. Initial, remote neurological exam was normal. Repetitive nerve stimulation revealed electrodiagnostic evidence of a post-synaptic neuromuscular junction disorder. Repeat in-person neurological exam was notable for limited bilateral upgaze, bilateral horizontal diplopia, bilateral orbicularis oculi and buccinator weakness, moderate guttural and lingual dysarthria,
and bilateral mild deltoid fatigability. The patient refused medical treatment but later underwent robotic thymectomy. Nearly six weeks after thymectomy, the patient presented to the ER with 1-2 week
history of dysarthia, dysphagia, and dyspnea, symptoms that began after receiving his second COVID vaccine shot. Inpatient neurological exam revealed mild right ptosis and left facial droop; NIFs were normal. The patient started pyridostigmine but refused disease-modifying treatment.


This case illustrates the potential for developing myasthenia gravis symptoms both pre- and post thymectomy in patients found to have incidental thymomas.