Case Report: A rare motor storm in lupus: opsoclonus-myoclonus-ataxia syndrome as an atypical presentation of severe systemic lupus erythematosus.

Background: Opsoclonus-myoclonus-ataxia syndrome (OMAS) is a rare hyperkinetic movement disorder characterized by opsoclonus, generalized myoclonus, and cerebellar ataxia. In adults, OMAS is most often reported in paraneoplastic or postinfectious settings, whereas autoimmune etiologies are less common. Case presentation: A 21-year-old woman with a 7-month history of SLE developed a 3-week subacute OMAS phenotype with opsoclonus, generalized myoclonus, and gait/limb ataxia, leading to loss of independent ambulation. CSF, microbiological testing, and brain MRI were unremarkable, and initial malignancy screening was negative. Severe lupus activity was documented (SLEDAI-2 K 27). She received methylprednisolone pulses, plasmapheresis, and rituximab, with progressive neurological recovery and a decrease in lupus activity to SLEDAI-2 K 4. At discharge, she ambulated independently with mild residual gait ataxia. Conclusion: This case expands the spectrum of neuropsychiatric SLE by illustrating OMAS as a predominantly motor phenotype. A structured evaluation to exclude structural, infectious, and malignant etiologies is essential, and early escalation of immunotherapy may be associated with substantial neurological recovery when OMAS occurs in the context of severe lupus activity.