To the Editor: Following the letter by Kitson et al, about a patient with asymptomatic ocular syphilis,1 we describe another unusual presentation of syphilis, with perioptic neuritis that mimicked papilloedema.

A 28-year-old man presented with blurry central vision of his right eye on waking. He had had flu-like symptoms 2 days before presentation. There were no symptoms suggestive of meningitis, no raised intracranial pressure and no obvious ocular infection or inflammation. He had been diagnosed with type 2 diabetes mellitus at age 15 years, and had no known microvascular complications. His only medication was metformin.

His visual acuity was 6/12 in the right eye and 6/6 in the left. The right eye had an enlarged blind spot with a small paracentral scotoma, with a central relative scotoma to red. The visual field in the left eye was normal. There was no relative afferent pupillary defect, and the anterior chambers were normal. Fundoscopy confirmed bilateral swelling of the optic discs (Box).

Computed tomography and magnetic resonance imaging of the brain excluded space-occupying lesions and demyelination. Examination of the cerebrospinal fluid (CSF) showed: normal opening pressure; a white cell count of 66 × 109/L (reference range, 4–11 × 109/L), 100% lymphocytes; a protein concentration of 1.12 g/L (reference range, 0.15–0.45 g/L); a glucose concentration of 8.9 mmol/L (reference range, 2.7–4.4 mmol/L); and no bacterial growth. Findings of a baseline blood analysis were normal, but with an elevated glycated haemoglobin (HbA1c) level of 10.5% (reference range, < 6%), indicating poorly controlled diabetes.

We thus initially considered diabetic papillopathy and non-arteritic ischaemic optic neuropathy, but the patient subsequently (about a week later, after most other investigations gave negative results) reported having had unprotected sexual intercourse with different men about 5 months previously. He recalled having a transient palmar maculopapular rash 2 months before presentation. Neurosyphilis was then confirmed with a strongly positive result on an absorbed fluorescent treponemal antibody (FTA-ABS) test in CSF. Results of serological tests for syphilis were positive (reactive [3+] on a Treponema pallidum particle agglutination test and a markedly elevated titre on a rapid plasma reagin test [1:128]), but results of tests for HIV and hepatitis were negative. Contact tracing was initiated.

After 21 days of treatment with intravenous penicillin, the vision in his right eye was completely restored. At 9-month follow-up, the bilateral swelling in his optic discs had resolved, and there was a tenfold decline in the rapid plasma reagin test titre (1:8).

This case illustrates syphilitic perioptic neuritis with optic disc swelling that is indistinguishable from papilloedema. Perioptic neuritis describes inflammatory involvement of the optic nerve sheath without inflammation of the nerve itself. The affected eye often has normal visual acuity with no visual field defect except for an enlarged blind spot.2,3

The prevalence of infectious syphilis has been rising in recent years, especially in Victoria and New South Wales, predominantly among men who have sex with men.4,5 Endemic syphilis should also be considered in patients with HIV co-infection and Indigenous patients, particularly those in the remote communities of Western Australia. Physicians should be vigilant in looking for neurosyphilis in any sexually active individual with unexplained eye or neurological signs.

The swollen optic discs of a patient with syphilitic perioptic neuritis