Myasthenic syndrome in systemic lupus erythematosus successfully treated with plasma exchange: through one of the unexplored faces of neuropsychiatric involvement.

Neuropsychiatric systemic lupus erythematosus (NPSLE) encompasses a wide range of neurological manifestations, including, though rarely, myasthenia gravis (MG). We report the case of a 47-year-old woman with long-standing systemic lupus erythematosus (SLE) who developed diplopia and fluctuating muscle weakness. Electromyography revealed a decremental response to low-frequency stimulation in the absence of MG-specific autoantibodies. These neurological features were interpreted as manifestations of NPSLE and were initially treated with azathioprine and then rituximab, the latter discontinued due to an adverse reaction. Several years later, immunosuppressive therapy with mycophenolate mofetil and voclosporin was initiated following a renal flare. Although renal remission was achieved, the patient experienced a concomitant relapse of neurological symptoms. After multidisciplinary consultation with neurologists, the patient underwent 3 monthly cycles of plasma exchange combined with corticosteroid pulses, resulting in marked clinical improvement of neurologic symptoms and sustained serological and clinical stability during the follow-up. The coexistence of SLE and MG is uncommon; distinguishing between an overlap syndrome or lupus-related myasthenic manifestations and choosing the optimal therapeutic strategy remain challenging. In this case, plasma exchange proved to be an effective rescue therapy, highlighting the importance of a multidisciplinary approach and individualized treatment strategies in managing complex NPSLE presentations.