Toxoplasmosis – September 2019

History

A 50-year-old man presented urgently with blurred central vision in his right eye.  It had started 5 days prior and progressively worsened to the point that he felt he could barely see anything in front of his face.  The patient denied pain, redness, irritation, flashes or floaters and had no recent illness, no headaches, no difficulty breathing, and no stomach issues. He had no significant medical history, no ocular history, and was on no medications.

Exam

Vision was CF (count fingers) in his right eye and 20/25 in his left eye.  IOP was 48 and 16 in the right and left eyes, respectively.  Confrontation visual fields showed a central area of field loss OD, but periphery was intact otherwise.  Anterior segment exam was significant for trace cell OD.

Evaluation of his posterior segment demonstrated rare vitreous cell OD.  Below are his fundus photos:

Right eye demonstrated a macular, deep retinal white lesion with multiple punctate surrounding lesions; inferiority there was also an area of RPE scarring.

Left fundus was unremarkable

 

Fluorescein Angiogram of the right eye (below) demonstrated leakage of the central macular lesion and staining of the inferior, peripheral lesion.

 

 

OCT: Left eye (top image) demonstrated normal foveal contour and no abnormality of the retinal layers or RPE; Right eye (bottom image) showed intraretinal distortion with loss of foveal contour and hyper reflective material in the outer layers.

Differential Diagnosis:

  • Toxoplasmosis
  • Syphilis
  • Tuberculosis
  • Sarcoidosis
  • Viral Retinitis (CMV, HSV, VZV)
  • Bartonella

Discussion:

Outer Retinal Toxoplasmosis Chorioretinitis 

Toxoplasmosis is the most common infectious chorioretinitis in humans.  The organism, Toxoplasma gondii, is found in a wide range of animals but the definitive hosts are cats.  Rates of human infection are highest in tropical areas with most cases found in patients from locations such as Brazil and Africa.

Patients typically complain of floaters and blurred vision. The classic finding is described as a “headlight in the fog” demonstrating a white, focal retinitis with overlying vitreous inflammation. Often, there is a nearby pigmented retinochoroidal scar.  Other common findings include keratic precipitates, inflammatory ocular hypertension, and retinal vasculitis.  Diagnosis is mainly clinical, but the use of IgG titers is reassuring and can help rule-out disease.  PCR of aqueous humor or vitreous fluid can be helpful in atypical cases.

Not all lesions require treatment, but in our patient, it was both macular threatening and he had significant visual impairment.  Other indications include optic nerve lesions, large lesions, immunocompromised patients, or pregnant patients.  Treatment involves “triple therapy” with a combination of systemic pyrimethamine, sulfadiazine, and corticosteroids.  The addition of Bactrim, clindamycin, or azithromycin is also used in high risk lesions or atypical cases.  The patient was started on triple therapy plus Bactrim as well as timolol for the elevated IOP and is scheduled for close follow-up.

References:

  1. Kim SJ, Scott IU, Brown GC, Brown MM, Ho AC, Ip MS, Recchia FM. Interventions for toxoplasma retinochoroiditis: a report by the American Academy of Ophthalmology. Ophthalmology. 2013 Feb;120(2):371-8. doi: 10.1016/j.ophtha.2012.07.061. Epub 2012 Oct 11. Review. PubMed PMID: 23062648
  2. Schachat et al; Ocular Toxoplasmosis, Chapter 88; Ryan’s Retina, 6th Ed.

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