Case Presentation: A 42 year-old woman with no significant past medical history presented with a one-week history of sudden bilateral vision loss. Two weeks prior, she reported new bifrontal, pounding headaches with subsequent blurring of vision in her right eye. After two weeks, her headaches suddenly disappeared with sudden bilateral, painless blindness. Evaluation by a local optometrist revealed bilateral papilledema and she was admitted for further workup. Physical exam revealed 20/200 vision in her right eye and complete blindness in her left eye with bilateral pupillary dilation, afferent pupillary defects, and no color discernment in the right eye. Lumbar puncture showed normal opening pressures, protein, and 0 inflammatory cells. Laboratory workup revealed negative cerebrospinal fluid (CSF) and serum VDRL, rapid plasma reagin, syphilis IgG, herpes simplex virus/Epstein-Barr virus, cryptococcal antigen, oligoclonal bands, serum protein electrophoresis, anti-nuclear antigen, hepatitis serologies, Quantiferon Gold, Bartonella IgG, and malignant cells. Magnetic resonance imaging revealed edematous T2 hyperintense bilateral optic nerve enhancement suggestive of optic neuritis (ON). Further workup demonstrated negative neuromyelitis optica/aquaporin 4-IgG and positive myelin oligodendrocyte glycoprotein (MOG)-IgG with >1:100 titer. Treatment for her bilateral MOG-IgG optic neuritis was initiated with pulse-dose methylprednisolone 1000 milligrams (mg) daily for three days followed by plasma exchange for five total sessions. She was discharged on a steroid taper with close follow-up with Neuro-ophthalmology and Neurology. Her visual acuity improved to 20/40 (right) and 20/50 (left) with persistent optic disc pallor, and she was prescribed mycophenolate mofetil 2000 mg daily for maintenance immunosuppression.
Discussion: Vision loss is a common presenting symptom for general internists; however, sudden bilateral vision loss significantly narrows the differential to autoimmune, neurologic, infectious, endocrine, and iatrogenic etiologies. MOG-IgG associated disease (MOGAD) is a spectrum disorder characterized by destruction of mature oligodendrocytes, commonly the myelin sheath surrounding the optic nerve, by MOG-specific CD4+ T cells and antibodies1. MOGAD can present with a range of relapsing syndromes including acute disseminated encephalomyelitis (fever, headache, nausea, altered mental status), isolated ON, transverse myelitis, or brainstem/cortical inflammation. Diagnosis of MOGAD requires three necessary components: a clinical picture consistent with MOGAD, neuroimaging or neurophysiology exam indicating demyelinating central nervous system injury, and biochemical testing with positive anti-MOG IgG4. Early treatment includes high-dose methylprednisolone or intravenous immunoglobulin followed by maintenance immunomodulatory therapy2. Early initiation of maintenance immunosuppressive therapies has shown a 49% reduction in MOG-IgG ON flares; thus, timely follow-up with Neurology and Ophthalmology is paramount to mitigate future relapse3.
Conclusions: Sudden bilateral blindness should raise suspicion for MOG-IgG optic neuritis for the general internist. Early MRI imaging, serum/CSF immunologic testing, intensive medical therapy with corticosteroids/PLEX, and initiation of maintenance immunomodulatory therapy is essential to diagnose and treat acute ON and prevent future flares.