Syphilis is known as a great masquerader because of its wide range of presentations.[[1]] It is a vision-threatening sexually transmittable infection (STI), and its presentation with posterior uveitis is more likely with human immunodeficiency virus (HIV) co-infection. Rates of syphilis in New Zealand are on the rise.

Case report

A 39-year-old, otherwise-healthy Māori male presented to a regional centre with decreasing vision in the left eye for four weeks. His best corrected visual acuities (BCVA) were 6/4 in the right eye and hand movements in the left eye. Intraocular pressures were normal. His history revealed multiple unprotected sexual intercourses with male and female partners. His left eye had panuveitis with the following exam findings: conjunctival ciliary injection, non-granulomatous keratic precipitates, anterior chamber 2 plus cells and flare (Figure 1), posterior synechiae, vitritis with snowballs and chorioretinitis with periphlebitis and arteritis (Figure 2). The right eye was normal on exam.

Extensive investigations were requested, including polymerase chain reaction from an aqueous sample. Treatment for toxoplasma (co-trimoxazole 960mg orally twice a day) and acute retinal necrosis (valaciclovir 2g orally three times a day) was commenced while we awaited the results of his investigations. He was also placed on topical Pred Forte hourly and cyclopentolate 1% three times a day for the anterior chamber inflammation.

His investigations were positive for syphilis and HIV. An urgent referral to infectious diseases was made and he was commenced on intravenous penicillin 2.4 grams every four hours for syphilis and high active antiretroviral therapy (dolutegravir, tenofovir disoproxil and emtricitabine) for HIV. Oral valaciclovir and co-trimoxazole were stopped when aqueous sampling was negative for toxoplasma, herpes simplex, varicella zoster and cytomegalovirus.

Seven days after diagnosis he developed cystoid macular oedema (CMO) and required peribulbar triamcinolone (Figure 3). His BCVA on 5 May 2021 with resolving CMO was 6/18. Room for visual improvement was expected.

Figure 1: Anterior chamber photograph two days after presentation and commencing of treatment.

Figure 2: Colour fundus (right) and fundus fluorescein angiogram (left) photograph of the left eye with effected structures labelled.

Figure 3: OCT images show cross-sections of the macula before and after treatment with anti-VEGF intravitreal injection.

Discussion

The prevalence of syphilis in New Zealand is increasing at an alarming rate among men who have sex with men (70% of cases) and heterosexuals.[[2,3]] There was a six-fold increase in cases between 2013 (n=82) and 2018 (n=543) when population growth was only 11%.[[3]] Māori men and men placed on pre-exposure prophylaxis for HIV are disproportionately afflicted.[[4,5]]

Treatment for ocular syphilis is the same as for neurosyphilis;[[3]] hence our rationale for commencing intravenous penicillin in our patient.[[5]] Posterior segment involvement is more prevalent with HIV co-infection[[3]] and is indicated by floaters in the history. Syphilis chancre increases the risk of HIV transmission[[6]] with up to 40% co-infection reported in the literature.[[7]] Our patient was not immunocompromised, but the management of his ocular syphilis would have been no different if he was. He was observed closely during the first 24 hours of treatment for Jarisch-Herxheimer reaction, an immune response towards syphilitic-endotoxin-like products that creates further ocular inflammation and irreversible vision loss if not treated promptly with systemic steroids.[[8]] Our patient was fortunate enough to not experience this.

Vision loss with ciliary injection, photophobia and floaters indicates uveitis with posterior segment involvement and requires prompt referral to ophthalmology for further investigations, including the consideration of STIs. It is important for healthcare professionals to be cognisant of the increasing incidence of syphilis in New Zealand and its association with HIV.