Myasthenia Gravis as a Paraneoplastic Manifestation of Renal Cell Carcinoma: More Than a Coincidence?

Background: Myasthenia gravis is an autoimmune neuromuscular disease primarily caused by autoantibodies against nicotinic acetylcholine receptors (AChRs) at the neuromuscular junction. However, extrathymic malignancies need to be considered in the elderly population.

Purpose: Although thymic malignancy is the most common tumour association, several extrathymic malignancies complicated with myasthenia gravis have been reported. During the review of the literature, there are only a few reports of myasthenia occurring as a paraneoplastic manifestation of renal cell carcinoma.

Methods: We present a 64-year-old elderly gentleman with progressive weakness. The patient underwent routine blood investigations, AChR antibody testing repetitive nerve stimulation test (RNST), contrast-enhanced computed tomography of the abdomen and radical nephrectomy with histopathological analysis.

Results: The patient improved significantly with immune modulatory therapies and underwent surgical intervention. He also later started on adjuvant chemotherapy based on histopathological reports and analysis. This case highlights the need for evaluation of extrathymic malignancy in late-onset myasthenia gravis.

Conclusion: Our case highlights the need for screening for extrathymic malignancies in patients presenting with late-onset myasthenia gravis, which had good outcomes if identified early initiation of treatment.