###Rationale: Ans. b. Ocular toxoplasmosis (Ref: Parson's 21/e p242-43; Kanski 7/e p429-30, 457-63; Yanoff Ducker 3/e p828-30, 785; Harrison 19/e 40e-6f 1400, 1402, 1404, 18/e p229, 1724, 1726)A 32-year-old male presents with unilateral diminished vision in the right eye. On examination, there is mild iritis, vitretis and a focal necrotic lesion is seen at the macula. The most likely diagnosis is ocular toxoplasmosis."Ocular toxoplasmosis presents with localized necrotizing chorioretinitis involving macula, satellite lesions, spill over granular anterior uveitis, vitritis (leading to head light in fog appearance) with floaters (due to vitritis), diminished vision, pain, redness and photophobia in young adults/infants."Ocular ToxoplasmosisToxoplasmosis is one of the most frequently identifiable causes of uveitis worldwide.MC cause of infectious posterior uveitis in non-immunocompromised individualsQ2nd MC cause of infectious posterior uveitis in patients with HIV/AIDS (MC cause: CMV retinitis)QIt usually presents in infants or adults of 10-35 yearsQ.Clinical Features:Depends on patient age, location, size and severity of retinochoroiditis.Ocular manifestations include floaters and blurred vision.Decreased visual acuity may occur as a result of macular involvement or severe vitreous inflammation.Ocular toxoplasmosis presents withNecrotizing chorioretinitis (destroying choroid and retina producing punched out heavily pigmented macular scar)QSatellite lesion (solitary inflammatory focus near old pigmented scar)Spill over anterior uveitis (may be granular resembling Fuchs syndrome)Severe vitritis (so dense as to prohibit an adequate view of posterior segment i.e. head light in fog appearance)Q.Bilateral macular involvement is common (in immunocompromised).Triad of congenital toxoplasmosis: Convulsion + Chorioretinitis + Intraeranial calcificationQDiagnosis:Diagnosis of ocular toxoplasmosis is often made by clinical features.Diagnostic tests include demonstration of parasite. Sabin-Feldman dye test (serological test require live T. gondii organism with a titer >1:16), complement fixation test, indirect hemagglutination test and ELISA for IgG and IgM.Treatment:MC treatment for ocular toxoplasmosis (''classic therapy"): Pyrimethamine and sulfadiazine plus corticosteroidsQ.Alternative treatment: Quadruple drug therapy (classic regimen plus clindamycin), as well as single or combined use of clindamycin, trimethoprim/sulfamethoxazole, spiramycin, minocycline, azithromycin, atovaquone and clarithromycin.

###Answer: OPTION B IS CORRECT.
###Question: A 32-year old male presents with unilateral diminished vision in the right eye. On examination, there is mild iritis, vitretis and a focal necrotic lesion is seen at the macula. The most likely diagnosis is:
###Options:
A. Multiple Evanescent White Dot syndrome
B. Ocular toxoplasmosis
C. Multifocal chorioditis
D. Ocular sarcoidosis
