Serotonin Syndrome-Mimicking Manifestations in a Patient with Systemic Lupus Erythematosus

Neuropsychiatric systemic lupus erythematosus (NPSLE) is a complication of systemic lupus erythematosus with diverse clinical presentations sharing common features with variable neurologic disorders. Magnetic resonance imaging (MRI) may provide imaging evidence of structural brain abnormalities associated with symptoms of NPSLE. Serotonin syndrome is a toxidrome characterized by altered mental status, autonomic hyperactivity, and neuromuscular abnormalities. It is mostly caused by medications that increase serotonin and is rarely reported as a manifestation of neuropsychiatric lupus. We presented the case of a 24-year-old Taiwanese woman with a history of systemic lupus erythematosus diagnosed at 21 years of age. The initial clinical and laboratory presentations upon diagnosis included fever, arthritis, hypocomplementemia, positive antinuclear antibody, anti-double-stranded DNA antibody, and anti-ribosomal P antibody. Her condition once remained stable under oral glucocorticoids and immunosuppressants, but she developed sudden-onset consciousness disturbance, incoherent speech, and unsteady gait ten days before our assessment. A high fever of up to 39 °C with tremor and clonus occurred at the intensive care unit. Brain MRI revealed symmetric T2 hyperintensity without diffusion restriction over the bilateral globus pallidus. High-dose pulse glucocorticoid and rituximab were prescribed during her admission and the neuropsychiatric symptoms diminished upon treatment. No alternation in mental status or involuntary movements were noted at follow-up. Our patient was diagnosed with neuropsychiatric lupus, with clinical symptoms and image findings mimicking those of serotonin syndrome. Neuroimaging, such as MRI, detects various structural brain abnormalities and may provide pathophysiological evidence of clinical manifestations.