Serum AQP4-IgG and MOG-IgG double positivity presenting as cerebral salt-wasting syndrome superimposed on area postrema syndrome: a case report

Background Neuromyelitis optica spectrum disorders (NMOSD) and myelin oligodendrocyte glycoprotein antibody-associated disorders (MOGAD) are autoimmune diseases of the central nervous system associated with AQP4-IgG and MOG-IgG, respectively. The coexistence of serum AQP4-IgG and MOG-IgG is relatively uncommon, and its clinical significance remains to be eluciated. In previously reported cases, patients with dual seropositivity have typically presented with opic neuritis or myelitis. Case presentation: A 55-year-old Chinese female presented with intractable hiccups, nausea, vomiting, and dizziness. Imaging revealed involvement of the brainstem and adjacent structures, accompanied by refractory hyponatremia. Further investigation demonstrated markedly elevated 24-hour urinary sodium excretion and dual positivity for AQP4-IgG and MOG-IgG. She was ultimately diagnosed with AQP4-IgG and MOG-IgG double positivity manifesting primarily as cerebral salt-wasting syndrome superimposed on posterior fossa syndrome. The patient’s symptoms improved rapidly following acute-phase glucocorticoid therapy Subsequent maintenance immunosuppressive with azathioprine was initiated, and serum sodium levels normalized. No recurrence was observed during follow-up. Conclusion: This case highlights that in patients with unexplained hyponatremia accompanied by intractable vomiting and hiccups, NMOSD or MOGAD spectrum disorders should be considered in the differential diagnosis. Early optimization of relevant antibody testing and neuroimaging is essential, and individualized immunotherapy targeting the underlying etiology should be implemented to improve outcomes and reduce the risk of recurrence.