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 . 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 . 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, 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 . 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 . 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 . 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 . 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.
“White retinal lesion”
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