A full laboratory work-up for the patient’s optic neuritis was also obtained, including antineutrophil cytoplasmic antibodies (ANCA), angiotensin-converting enzyme (ACE), antinuclear antibody (ANA), syphilis, human immunodeficiency virus (HIV), Lyme disease, tuberculosis, and erythrocyte sedimentation rate (ESR). The gene discussed is ACE; the disease is syphilis.