Sequential Bilateral Optic Neuropathy Associated With IgM-Secreting B-cell Non-Hodgkin Lymphoma

Optic neuropathy associated with hematologic malignancy may present with heterogeneous clinical and radiographic findings, creating diagnostic uncertainty.We report the case of a 76-year-old man with vascular risk factors who developed new-onset, painless vision loss in the right eye accompanied by optic disc edema.Cerebral angiography identified a dural arteriovenous (AV) fistula with feeding-artery aneurysms, and subsequent evaluation demonstrated left internal carotid artery stenosis, presenting competing vascular explanations during the diagnostic evaluation.Vision did not improve following vascular intervention or high-dose corticosteroid therapy, and two orbital MRI examinations revealed no abnormalities.Approximately one year later, the patient developed new vision loss in the previously unaffected left eye, with sequential optic disc edema followed by bilateral optic atrophy and severe visual-field loss.Expanded systemic evaluation revealed an IgM monoclonal gammopathy, and bone marrow biopsy demonstrated CD5-/CD10-B-cell non-Hodgkin lymphoma involving 20-25% of marrow cellularity.Following the initiation of zanubrutinib, serum IgM levels declined; however, objective visual fields remained severely depressed despite subjective improvement in daytime vision.Although an association between the lymphoproliferative disorder and optic neuropathy is biologically plausible, the available clinical data do not establish causation or a definitive mechanism of optic nerve injury, and competing etiologies could not be completely excluded.This report highlights the importance of continued systemic evaluation when sequential optic neuropathy remains unexplained despite nondiagnostic neuroimaging.In selected patients, hematologic evaluation, including serum protein electrophoresis, may identify an underlying monoclonal gammopathy or lymphoproliferative disorder.