Case Report: Thymoma-associated stiff person syndrome and myasthenia gravis: an index case with exploratory exome sequencing and review of reported cases

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Thymoma is frequently associated with myasthenia gravis (MG), but the coexistence of stiff person syndrome (SPS) is rare and presents diagnostic challenges.
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A 55-year-old female with thymoma-related SPS and MG showed significant symptoms, including gait instability and dysphagia, and responded well to immunotherapy and thymectomy.
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Whole-exome sequencing of the thymoma revealed a CACNA1A mutation and variants in immune-signaling genes, highlighting pathways related to calcium channels and GABAergic synapses.
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The literature review identified seven additional cases of thymoma-associated SPS and MG, typically characterized by GAD65 positivity and favorable outcomes with treatment.
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The findings support a unifying mechanism involving thymic neoplasia, impaired inhibitory neurotransmission, and autoimmunity at the neuromuscular junction.

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