A diagnostic challenge: syphilitic optic neuropathy

Syphilitic optic neuropathy is an uncommon but treatable cause of visual loss and may occur as an isolated manifestation of neurosyphilis. We report a 72-year-old man who presented with progressive painless unilateral visual loss. He was initially diagnosed as non-arteritic anterior ischemic optic neuropathy but later developed progressive worsening, optic nerve MRI abnormalities and delayed visual evoked potentials. Other causes of optic neuropathies, such as demyelination were considered. Despite immunotherapy, vision continued to deteriorate. Subsequent investigations demonstrated positive serum VDRL and TPPA. With the exclusion of other causes of chronic optic neuropathy, syphilitic optic neuropathy was diagnosed. Treatment with intravenous benzylpenicillin stabilized vision, although established optic atrophy prevented visual recovery. This case highlights the diagnostic challenges and emphasizes the importance of routine syphilis serology in atypical, progressive, or treatment-refractory optic neuropathies.