Among infectious posterior uveitis, which is more likely to cause vitritis?

• A. Histoplasmosis
• B. Toxoplasmosis
• C. CMV retinitis
• D. Endophthalmitis

Answer: (B)

Vitritis, or inflammatory cells in the vitreous, is most strongly associated with toxoplasmosis in infectious posterior uveitis. Toxoplasma retinochoroiditis typically involves a focal retinal lesion with a vigorous inflammatory response that spills into the surrounding vitreous, creating dense vitreous haze and the classic “headlight in a fog” appearance. This pronounced vitreous reaction reflects the close inflammatory connection between the retina and vitreous in toxoplasmosis.

Histoplasmosis usually presents with chorioretinal granulomas and scars with less prominent vitreous inflammation. CMV retinitis, especially in immunocompromised patients, tends to show necrotizing retinal lesions with relatively limited early vitreous reaction, rather than dense vitritis. Endophthalmitis involves infection of multiple ocular tissues and generally presents with widespread inflammation beyond the posterior segment, so it isn’t the posteriority pattern described.

So the organism best known for producing dense vitritis in infectious posterior uveitis is toxoplasmosis.