Which etiology of posterior uveitis is LEAST likely to cause vitritis?

• A. Toxoplasmosis
• B. Sarcoidosis
• C. Histoplasmosis
• D. Syphilis

Answer: (C)

The amount of vitreous inflammation helps differentiate posterior uveitis etiologies. Some conditions characteristically produce a lot of inflammatory cells in the vitreous, while others spare it.

Toxoplasmosis classically causes dense vitreous haze with a focal retinochoroiditis, giving a prominent vitritis. Sarcoidosis often presents as a granulomatous uveitis with vitreous cells and sometimes “snowball” inflammatory aggregates. Syphilis can also present with posterior uveitis that includes notable vitreous inflammation.

Histoplasmosis, in its ocular histoplasmosis syndrome form, typically shows chorioretinal atrophy and punched-out lesions with relatively little vitreous inflammation. The vitreous is often quiet unless there is active retinitis. Because of this pattern, histoplasmosis is least likely among the options to cause significant vitritis.