What is the most common cause of posterior uveitis in the United States?

• A. Toxoplasmosis
• B. Sarcoidosis
• C. Cytomegalovirus retinitis
• D. Birdshot chorioretinopathy

Answer: (A)

In posterior uveitis, infection with Toxoplasma gondii is the most common cause in the United States. Toxoplasmosis produces focal retinochoroiditis, often presenting as a unilateral, necrotizing retinal lesion with overlying vitritis. The widespread, latent exposure to Toxoplasma makes it the leading cause of these inflammatory eye findings.

Other options reflect less common scenarios: CMV retinitis appears mainly in severely immunocompromised patients and has a characteristic necrotizing retinitis with hemorrhages; birdshot chorioretinopathy is a rare, bilateral, noninfectious uveitis with distinctive mid-peripheral cream-colored lesions; sarcoidosis can cause granulomatous posterior uveitis but is not as frequent a cause as toxoplasmosis.