Isolated presumed optic nerve gumma, a rare presentation of neurosyphilis

Purpose The incidence of syphilitic infections continues to rise and represents a major public health concern, particularly in patients co-infected with human immunodeficiency virus (HIV). The infection has a multitude of clinical presentations and is often referred to as the 'great imitator.' We present a rare case of an isolated presumed syphilitic optic nerve gumma and characterize it using newer imaging modalities. Observations A 36-year-old HIV-positive man, compliant with treatment, presented with a five day history of decreased vision in the left eye. On examination his visual acuity was 20/30 with mild dyschromatopsia and an inferior altitudinal field defect in the left eye. Funduscopy demonstrated small cup to disc ratios bilaterally and a swollen and hyperemic left optic disc. Following five months of stable vision, the patient's vision in the left eye declined to 20/60, associated with diffuse visual field loss and continued swelling of the left optic disc. Subsequent magnetic resonance imaging with contrast demonstrated enhancement of the left optic nerve, and his serologies were positive for syphilis. Fluorescein angiography and optical coherence tomography were used to better characterize the lesion being most consistent with a syphilitic optic nerve gumma. Conclusions and importance Gummas of the central nervous system are a rare presentation of neurosyphilis and the last reported gumma of the optic nerve was in 1990. Such lesions have not been characterized using newer imaging modalities including optical coherence tomography and fluorescein angiography, both of which may assist in the diagnosis of this rare entity. With the increased prevalence of syphilis and remarkable response to therapy, syphilitic gummas should be considered in at-risk patients presenting with an optic neuropathy.