Broadening NMOSD etiology: neurosyphilis as a mimicry factor

Address for correspondence: Marco A. Lana Peixoto (email: [e-mail]).

Abstract

Neuromyelitis optica spectrum disorders (NMOSD) are autoimmune conditions most commonly associated with aquaporin-4 or MOG autoimmunity. Double-seronegative NMOSD encompasses a 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. We herein present a case of a patient who developed simultaneous bilateral optic neuritis and myelitis due to neurosyphilis. 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, as well as sphincter disturbances. Upon examination, his visual acuity (VA) was of 20/80 in the right eye and of 20/200 in the left eye. The fundoscopic examination was unremarkable. The neurological examination revealed quadriparesis and loss of light touch and vibration sense in the lower limbs. The EDSS score was of 5.0. A Brain MRI scan showed T2/FLAIR large lesions in both cerebral hemispheres, cerebellar peduncles, and the pontomesencephalic junction. A spinal MRI scan showed a longitudinally-extensive T2 lesion from the cervicomedullary junction to the level of T2. The patient tested negative for AQP4-IgG and positive for syphilis; MOG-IgG was not tested. The CSF analysis demonstrated 13 white blood cells/mm³ with 8% of neutrophils, and protein content of 93 mg%, with a negative VDRL test. The patient was treated with IV crystalline penicillin but did not return for follow-up examinations. 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 to this report was the absence of MOG-IgG testing, despite MRI findings suggesting the possibility of MOGAD. This case could represent an instance of MOGAD coexisting with neurosyphilis.