Case Report

Initial Visit

A 33-year-old Hispanic male presented with a chief complaint of blurred vision and floaters OD for three days. Best corrected visual acuity was 20/20-1 OD and 20/20 OS. All other preliminary testing was normal. Anterior segment findings were normal and unremarkable in both eyes. Dilated fundus exam showed 1+ cell in the posterior vitreous. Inferior temporal to the optic nerve, there was an elevated chorioretinal lesion with an active-appearing foci at the inferior edge of the lesion (Figure 1). There was an overlying vitritis emanating mostly from the inferior portion of the lesion. Additionally, there were several small satellite lesions surrounding the lesion.

The most common underlying etiology for posterior uveitis is toxoplasmosis. Given the clinical findings, toxoplasmosis-associated posterior uveitis was suspected. A laboratory workup was conducted to aid in diagnosis and rule out other infectious etiologies. The Toxoplasma IgG antibody resulted in a high positive value of 210.00 IU/mL. The reference range for a “positive” result is >8.79 IU/mL. A positive Toxoplasma IgG result indicates infection with Toxoplasma gondii at some point in the past but does not differentiate between an active or past infection. All other labs ordered (Toxoplasma IgM antibody, FTA-ABS, RPR, QuantiFERON-TB Gold, CBC, CMP) were negative or within normal limits. 

The patient was diagnosed with suspected toxoplasmosis chorioretinitis OD. An anterior chamber paracentesis was deferred, given likely low yield due to the patient’s immunocompetent status and the mild level of inflammation. The patient was prescribed trimethoprim-sulfamethoxazole (TMP/SMX) 160mg/800mg twice daily by mouth and a 5-day follow-up was scheduled. Corticosteroids were deferred as adjunctive treatment at this time given the lack of anterior chamber reaction and relatively minimal posterior inflammation.

Follow-Up

The patient remained stable (Figures 2 and 3) at the first follow-up and was instructed to continue TMP/SMX and return in 3-4 weeks. At the one-month follow-up, the vitreous cell had resolved and the chorioretinal lesion and adjacent foci were distinct and inactive in appearance without overlying vitritis (Figures 4 and 5).  Given the resolution of vitritis and no evidence of other intraocular inflammation, the patient was instructed to discontinue treatment. The patient was scheduled to return in 3 months, or sooner if any recurrence of symptoms.

 

Discussion

Ocular toxoplasmosis occurs through infection of the parasite, Toxoplasma gondii, and accounts for approximately one-third of all posterior uveitis cases globally.1 Diagnosis is often clinical and can be supported by serologic testing for T. gondii–specific IgG and IgM antibodies. An AC tap to assess the aqueous humor for Toxoplasma DNA via PCR is the most definitive confirmatory method, however this is usually reserved for immunocompromised or atypical cases.2 Treatment with TMP/SMX has been shown to be as effective as pyrimethamine-sulfadiazine combinations, offering improved safety and accessibility.3 Adjunctive corticosteroids are reserved for cases with severe inflammation once other infections are excluded. Due to high recurrence rates, which can reach 79%, prophylactic TMP/SMX of one tablet every 3 days may be considered to reduce recurrence risk.4

Conclusion

In conclusion, chorioretinitis is often associated with toxoplasmosis as this is the leading cause of posterior uveitis. It is characterized by vitritis and chorioretinal lesions, which causes varying degrees of inflammation. Unfortunately, patients have high rates of recurrence, which often present as foci adjacent to old chorioretinal scars. A laboratory workup is indicated to help support clinical diagnosis and rule out other infectious etiologies which helps to guide treatment. Prompt treatment with antibiotics such as TMP/SMX is indicated when there is a high degree of clinical suspicion and subsequent corticosteroids should be considered. Treatment usually lasts for 4-6 weeks then prophylaxis may be considered in order to prevent recurrences and promote good visual outcomes in these patients.

References

  1. Karami M, Gorgani-Firouzjaee T, Rostami-Mansour S, Shirafkan H. Prevalence of Ocular Toxoplasmosis in the General Population and Uveitis Patients: A Systematic Review and Meta-Analysis. Ocul Immunol Inflamm. 2024;32(6):1003-1016. doi:10.1080/09273948.2023.2190801
  2. Garweg JG, de Groot-Mijnes JD, Montoya JG. Diagnostic Approach to Ocular Toxoplasmosis. Ocul Immunol Inflamm. 2011;19(4):255-261. doi:10.3109/09273948.2011.595872
  3. Soheilian M, Sadoughi MM, Ghajarnia M, et al. Prospective Randomized Trial of Trimethoprim/Sulfamethoxazole versus Pyrimethamine and Sulfadiazine in the Treatment of Ocular Toxoplasmosis. Ophthalmology. 2005;112(11):1876-1882. doi:10.1016/j.ophtha.2005.05.025
  4. Cifuentes-González C, Rojas-Carabali W, Pérez ÁO, et al. Risk factors for recurrences and visual impairment in patients with ocular toxoplasmosis: A systematic review and meta-analysis. PLoS One. 2023;18(4):e0283845. doi:10.1371/journal.pone.0283845