Unique association of anti-GABA A receptor encephalitis and myasthenia gravis in a patient with type A thymoma.

Association between anti-GABA _A R encephalitis and myasthenia gravis is extremely rare with few reported cases. Herein, we report a case of a female patient diagnosed with anti-GABA _A R encephalitis and thymoma at the first admission. She was administered glucocorticoids for long-term immunotherapy, and thymectomy with biopsy demonstrated a type A thymoma. After 4 months, the symptoms of encephalitis were relieved, but she then developed post-thymectomy myasthenia gravis with anti-AChR and anti-titin dual positivity. Antibodies to connective tissue (anti-ANA, anti-PCNA) and those characteristics of paraneoplastic syndrome (anti-Ma2/Ta) were also positive. She received oral glucocorticoids and tacrolimus as immunosuppressive therapy, and myasthenic symptoms were stable during a 2-year follow-up. Our case revealed that anti-GABA _A R encephalitis and myasthenia gravis can appear in patient with type A thymoma at different periods, which alerts physicians to take long-term follow-up for anti-GABA _A R encephalitis with thymoma, even after thymectomy. Concurrent positivity for more than one antibody after thymectomy is rarely observed, and their contribution to the clinical course and treatment decision remains to be further investigated.
(© 2023. Fondazione Società Italiana di Neurologia.)