A 25-year-old patient presents with unilateral vitritis. What is your top differential?

• A. ARMD
• B. Scleromalacia perforans
• C. Toxoplasmosis
• D. Histoplasmosis

Answer: (C)

Unilateral vitritis in a young adult points most strongly to ocular toxoplasmosis. Toxoplasma gondii causes focal retinochoroiditis with overlying vitreous inflammation, often in the posterior pole or mid-periphery. The patient’s age and the unilateral presentation fit this scenario, and the classic look is a white/gray focus with vitreous haze giving a “headlight in the fog” impression. The other options don’t fit as well: age-related macular degeneration is a disease of older patients with macular changes rather than active intraocular inflammation; scleromalacia perforans is a necrotizing scleral condition presenting with scleral thinning and scleral changes rather than a primary intraocular vitritis; histoplasmosis can cause posterior uveitis with chorioretinal scars, but it’s less typical in a 25-year-old and usually has different systemic or geographic context. So the presentation most consistent with the diagnosis is ocular toxoplasmosis.