Broadening NMOSD Etiology: Neurosyphilis as a Mimicry Factor

Introduction –Neuromyelitis optica spectrum disorders (NMOSD) are autoimmune conditons most commonly associated with aquaporin-4 or MOG autoimmunity.  Double seronegative NMOSD encompasses group of heterogenous diseases that may express typical manifestations of seropositive NMOSD.  Neurosyphilis can manifest with a broad range of neurological symptoms including optic neuritis and longitudinally extensive transverse myelitis. Objective – We presente a case  of a patient who developed simultaneous bilateral optic neuritis and myelitis due to neurosyphylis. Case Report - A 31-year-old man presented with subacute painful visual loss in both eyes accompanied by weakness and dysesthesia in the upper and lower limbs, and sphincter disturbances. On examination his visual acuity was (VA) of 20/80 in the right eye and 20/200 in the left eye. Fundoscopic examination was unremarkable. Neurological examination revealed quadriparesis and loss of light touch and vibration sense in the lower limbs. The EDSS was 5.0. Brain MRI showed  T2/FLAIR large lesions in both cerebral hemispheres, cerebellar peduncles, and the pons-mesencephalic junction. Spinal MRI showed a longitudinally extensive T2 lesion from the cervical-medullary junction to T2 level. The patient tested negative to AQP4-IgG, and positive for  syphilis. MOG-IgG was not tested. CSF analysis demonstrared 13 white blood cells/mm3 with 8% neutrophils; and protein content of 93 mg%, with a negative VDRL test. The patient was treated with IV cristalline penicillin but did not return for follow-up examinations. Conclusion - This case highlights the challenges in identifying the underlying cause in seronegative NMOSD. Clinicians should remain vigilant for alternative diagnoses to facilitate timely and appropriate treatment. A limitation of this report was the absence of MOG-IgG testing, despite MRI findings suggesting the possibility of MOGAD. This case could potentially represent an instance of MOGAD coexisting with neurosyphilis.