Which of the following is NOT true when comparing Toxoplasmosis to Histoplasmosis?

• A. Toxoplasmosis is more likely to have vitritis
• B. Toxoplasmosis will more likely have a unifocal lesion
• C. Toxoplasmosis will more likely develop into a CNVM
• D. Histoplasmosis is caused by a fungus while Toxoplasmosis is caused by a parasite

Answer: (C)

The key idea is how these infections typically present and what complications they tend to cause in the back of the eye. Toxoplasmosis usually shows a focal retinochoroiditis with prominent inflammatory cells in the vitreous—vitritis—often with a single, unilateral lesion and overlying vitreous inflammation. It’s not a disease classically linked to choroidal neovascular membranes.

Histoplasmosis, on the other hand, often presents as ocular histoplasmosis syndrome with peripheral chorioretinal scars and characteristic punched-out spots, little to no vitritis, and, importantly, a high risk of developing choroidal neovascular membranes that can threaten vision.

So saying that toxoplasmosis will more likely develop into a CNVM is not accurate; CNV is much more associated with histoplasmosis. Also remember the etiologies: toxoplasmosis is caused by Toxoplasma gondii (a parasite), while histoplasmosis is due to Histoplasma capsulatum (a fungus).