Anthony Tran, OMS IV and Anastasia Alpizar, OMS IV
William Carey University College of Osteopathic Medicine


Toxoplasma gondii is a parasite with the potential to infect humans, especially those who ‎are immunocompromised. If the parasite reaches the retina of the eye, it can cause ‎ocular toxoplasmosis, a potentially blinding infection of the eye. It is rare for an ‎immunocompetent individual to present with ocular toxoplasmosis; in this population, ‎toxoplasmosis typically presents as a mononucleosis-like illness and is self-limited. ‎However, in this case, a 51-year-old, immunocompetent patient presented strictly with ‎visual complaints and denied any systemic symptoms such as fever, chills, or fatigue. ‎This patient presented with blurred vision, photophobia, and visual impairment, ‎specifically reporting decreased vision in his right periphery. The patient’s dilated ‎fundoscopic exam demonstrated a fluffy white retinal lesion, a classic finding of toxoplasmic retinochoroiditis. ‎

Diagnosis can also involve serology such as testing for the presence of IgM and IgG ‎antibodies. Treatment is important because severe complications, including retinal ‎detachment and permanent vision loss, can occur. While the treatment prevents ‎progression, it is not curative. Recurrence of ocular toxoplasmosis is common as the ‎parasite can reactivate. In reactivation, the cysts rupture at the site of the scar’s border ‎and release parasites. Pyrimethamine-sulfadiazine and Trimethoprim-sulfamethoxazole ‎has been shown to reduce reactivation rates. However, patients should remain vigilant of ‎ophthalmic symptoms and should be followed closely. The risk of human toxoplasmosis ‎can be reduced by taking precautions such as cooking meats to adequate temperatures, ‎washing cutting boards, and wearing gloves where there is contact with soil or sand that ‎can be contaminated with cat feces.


Toxoplasma gondii is a parasite with the potential to infect humans. It is typically ‎acquired via ingestion of undercooked meat or consumption of cat feces, but may also ‎be congenital via transplacental transmission. Typically, the course is self-limited; ‎however the parasite does have the potential to cause more severe infections. ‎Immunocompromised individuals such as those with HIV, autoimmune disorders, and ‎chronic immunosuppression therapy are at the highest risk. One mechanism by which ‎this organism can cause harm is by proliferating in the retina and choroid, causing ocular ‎toxoplasmosis. Patients can present with symptoms including blurred vision, ‎photophobia, and visual impairment. Diagnosis can be made via dilated fundoscopic ‎exam, classically demonstrating a fluffy white retinal lesion [1]. The presence of a scar ‎indicates that healing has occurred, or it is inactive. Diagnosis can also involve serology ‎such as testing for the presence of IgM and IgG antibodies. Treatment is important ‎because severe complications, including retinal detachment and blindness, can occur [3]. ‎While the treatment prevents progression, it is not curative. Recurrence of ocular ‎toxoplasmosis is common as the parasite can reactivate. In reactivation, the cysts ‎rupture at the site of the scar’s border and release parasites [3]. Pyrimethamine-‎sulfadiazine, the standard therapy for toxoplasma infections, and trimethoprim-‎sulfamethoxazole (TMP-SMX), an alternative with comparable efficacy and safety, have ‎been shown to reduce recurrence rates [4]. However, patients should remain vigilant of ‎ophthalmic symptoms and should be followed closely. Patients who do not seek ‎treatment for ocular toxoplasmosis may experience permanent vision loss. ‎


A 51-year-old Caucasian male residing in Louisiana with no past medical history ‎presented to the outpatient ophthalmologist. The patient reported one week of vision ‎changes in the right eye including blurred vision and decreased visual acuity in a ‎temporal distribution. The patient denied any prior episodes of vision loss or ophthalmic ‎problems, recent travel, or ingestion of undercooked meat. The patient also denied any ‎recent organ transplant surgery. The patient recalled no exposure to cats or cat feces to ‎his knowledge. ‎

Dilated fundoscopic examination and imaging using laser scanning of the retina ‎demonstrated a localized white lesion in the periphery of the right retina with minimal ‎surrounding scarring. The fundus appeared hazy with inflammation. These findings were ‎compatible with an active posterior uveitis, with evidence that the immune response had ‎begun to wall off the lesion, resulting in early scar formation [1]. The macula was not ‎involved. These fundoscopic exam findings in the right eye were highly suspicious for ‎ocular toxoplasmosis, however it was also imperative that other pathogens were ruled ‎out. It is important to note that the left eye was examined and no significant physical ‎findings were noted. The patient was sent to the outpatient lab to obtain toxoplasmosis ‎antibodies, histoplasmosis antigen, rapid plasma regain (RPR), c-reactive protein (CRP), ‎erythrocyte sedimentation rate (ESR), Quantiferon-TB, HIV, cytomegalovirus (CMV), ‎and CBC with differential. Serology resulted with the presence of toxoplasmosis IgM ‎antibodies, which confirmed an acute ocular toxoplasmosis. The patient also received a ‎CT scan of the brain to rule out CNS involvement which would appear as ring-enhancing ‎lesions. The CT scan of the brain was negative for any abnormalities.‎

Patient’s symptoms began 7 days prior to appointment with the ophthalmologist, with ‎progressively worsening of his right temporal vision. The vision loss was described as ‎blurred, and he reported that this was worse with bright lights. The patient was seen by ‎the outpatient ophthalmologist and was started on TMP-SMX the same day for ‎presumptive treatment for a suspected case of toxoplasmosis. The patient was ‎prescribed 160 mg TMP/800 mg SMX, twice daily, for a total of six weeks. Treatment ‎with Pyrimethamine-Sulfadiazine was not financially possible for the patient. Patient was ‎referred to a retinal specialist for follow up, labs, and imaging two days after his initial ‎appointment. When the lab results confirmed the presence of Toxoplasma gondii, the ‎patient was instructed to continue TMP-SMX and complete the treatment.‎


In summary, this case is unique because it highlights a case of ocular toxoplasmosis in ‎an immunocompetent individual residing in the United States, which only occurs in 2% of ‎individuals infected with T. gondii in the United States [2]. Initial treatment of choice for ‎this patient was pyrimethamine plus sulfadiazine; however, given financial challenges ‎and evolving expert consensus, TMP-SMX is being identified as a regimen with ‎comparable efficacy and potentially fewer side effects [4,5]. As was seen in this case, ‎pyrimethamine can be expensive and in some countries difficult to obtain. Therefore, a ‎significant lesson taken from this case is the practicality of using TMP-SMX in place of ‎the pyrimethamine-sulfadiazine combination, which was historically utilized as the first-‎line treatment. ‎

Modes of transmission of Toxoplasma gondii commonly include ingestion of infectious ‎oocysts from the environment, undercooked meats, handling of cat feces, vertical ‎transmission, and through organ transplantation [3]. However, this patient denied ‎ingesting any questionable meats or any interactions with cats. Therefore, this case ‎demonstrates that the mode of transmission is not always easily proven or solved by the ‎patient’s history. Physicians and health care providers should suspect toxoplasmosis ‎even when the patient’s environmental exposures do not appear to be high risk for ‎Toxoplasma exposure. ‎


‎“Toxoplasma gondii”‎
“Ocular Toxoplasmosis”‎
‎“Blurred vision”‎
‎“White retinal lesion”‎


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