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| + | ====== Ocular Toxoplasmosis ====== | ||
| + | * Caused by Toxoplasma gondii | ||
| + | * Obligate intracellular protozoan | ||
| + | * 500 million have antibodies worldwide | ||
| + | * 50% of adult population in US have asymptomatic infection | ||
| + | * 28-55% of all cases of posterior uveitis | ||
| + | * First isolated from the brain of a " | ||
| + | * Cat family is definitive host, can infect other mammals and birds | ||
| + | * Oocysts found in intestinal tracts of cats | ||
| + | * Cysts ingested (most likely) | ||
| + | * Poor hygiene, infected pork, chicken but probably not beef | ||
| + | * Can survive outside host for up to 1 year | ||
| + | * Two forms in humans: cysts or tachyzoites. | ||
| + | * Propensity for cardiac and skeletal muscle and neural tissue (brain & eye) | ||
| + | ==== Clinical Manifestations ==== | ||
| + | === Acquired vs. Congenital === | ||
| + | * Most cases are presumed reactivation of congenital infection | ||
| + | * 2 to 6/1000 women acquire infection while pregnant, 40% risk of transmission to fetus. | ||
| + | * Of infected infants: 70% chorioretinal scars, 5% will die or severe disability, 1-2% severe visual impairment | ||
| + | * Northern Brazil has high rate of acquired disease | ||
| + | |||
| + | === Systemic === | ||
| + | * 90% lympadenopathy | ||
| + | * fever, malaise, occasional sore throat | ||
| + | * immunocompromised- fulminant CNS disease | ||
| + | |||
| + | === Ocular === | ||
| + | * Keratic Precipitates, | ||
| + | * Retinochoroiditis | ||
| + | * Vitritis- concentrated over lesion, scaffolding of vitreous strands | ||
| + | * Macular edema | ||
| + | * Retinal vasculitis | ||
| + | * VF defect in area of scar | ||
| + | * FFA of active lesion- early blockage and subsequent leakage | ||
| + | |||
| + | === Atypical Presentations === | ||
| + | * In early infection: gray-white fine punctate lesions in deep retina and RPE, progress to more classic lesions | ||
| + | * Papillitis, vitreal inflammation, | ||
| + | * Bullous like inflammatory lesions in mid-periphery | ||
| + | * Wide ring-like lesion near extreme periphery resembling pars planitis | ||
| + | * Scleritis | ||
| + | === Reasons for Vision Loss === | ||
| + | * Vitreal inflammation causing clouding | ||
| + | * Lesion in posterior pole with edema affecting fovea | ||
| + | * Lesion in fovea | ||
| + | * Subsequent CNVM | ||
| + | |||
| + | ==== Diagnosis ==== | ||
| + | * Typical lesions | ||
| + | * Toxoplasmosis titers are supportive | ||
| + | * IgM titers- can be missed | ||
| + | * IgG titers- high rate of false positives | ||
| + | * Immunoflourescence, | ||
| + | * Western blot for Toxo antigens | ||
| + | * PCR and Southern Blot for Toxo DNA | ||
| + | * Angiography: | ||
| + | |||
| + | ==== Therapy ==== | ||
| + | * Should you treat it at all? | ||
| + | * Lesion within temporal arcade | ||
| + | * Lesion next to optic nerve or large vessel | ||
| + | * Lesion has induced large degree of hemorrhage | ||
| + | * Vision drop of > two lines | ||
| + | * Multiple recurrences with vitreal contraction | ||
| + | * No truly randomized, controlled clinical trials to compare efficacy | ||
| + | * Generally 4-6 weeks, multi-drug regimens | ||
| + | |||
| + | ==== Medications ==== | ||
| + | * Sulfadiazine 1g PO QID | ||
| + | * Pyrimethamine 75-100mg load and 25-50mg PO BID (bone marrow suppression, | ||
| + | * Use concurrently: | ||
| + | * Clindamycin 150-300mg PO TID-QID (?reduces recurrence, risk of pseudomembranous colitis) | ||
| + | * Trimethoprim-sulfamethoxazole (DS) I PO BID | ||
| + | * Atovaquone (Mepron) 750mg PO BID (kills cysts in vitro) | ||
| + | * Tetracycline 2g load and 250mg PO QID (to replace clindamycin) | ||
| + | * Prednisone 20-60 mg/day not used alone | ||
| + | |||
| + | === Rothova et.al. (The Netherlands) Am J Ophth, 115: | ||
| + | == Treatment Regimen #1 == | ||
| + | * Pyrimethamine, | ||
| + | * Best at reducing size of lesions (49%), | ||
| + | * more medication side effects (26%), | ||
| + | * recurrence rate at 3 years (42%) | ||
| + | |||
| + | == Treatment Regimen #2 == | ||
| + | * Clindamycin, | ||
| + | * Reducing size of lesions >1/2 DD (28%) | ||
| + | * med side effects (17%) | ||
| + | * recurrence rate at 3 years (67%) | ||
| + | == Treatment Regimen #3 == | ||
| + | * Co-trimoxazole, | ||
| + | * Reducing size of lesions >1/2 DD (11%) | ||
| + | * med side effec!ts (4%) | ||
| + | * recurrence rate at 3 years (40%) | ||
| + | |||
| + | == Treatment Regimen #4 == | ||
| + | * No treatment (peripheral lesions) | ||
| + | * Reducing size of lesions >1/2 DD (20%) | ||
| + | * no med side effects | ||
| + | * recurrence rate at 3 years (53%) | ||
| + | |||
| + | == Comments == | ||
| + | * Recurrence rates not statistically significant | ||
| + | * Size of retinal lesion correlated with duration of inflammation | ||
| + | * All side-effects were reversible | ||
| + | * Delay in starting medication (even up to 1 week) did not alter duration of inflammation | ||
| + | * Sub-tenon' | ||
| + | * Vitrectomy- for vitreal haze reducing vision, perioperative antibiotics advocated | ||
| + | * Cryotherapy and Laser photocoagulation generally not successful | ||