A 68-year-old man presents with progressive bilateral floaters and blurred vision over six months. Examination shows dense vitritis with clumps of cells described as balls of snow, multifocal cream-colored sub-retinal pigment epithelial infiltrates, and little anterior chamber reaction. He had transient improvement then worsening on oral corticosteroids. Contrast MRI brain shows periventricular white matter lesions. The most useful next investigation is:

• A Diagnostic vitrectomy with cytology and interleukin-10 to interleukin-6 ratio ✓
• B Serum angiotensin converting enzyme level
• C Treponemal serology
• D Quantiferon-TB gold assay

Explanation

Primary intraocular lymphoma, usually a diffuse large A-cell lymphoma of the central nervous system, is the great steroid-resistant masquerade of older adults with vitritis, sub-RPE cream-colored infiltrates, and brain lesions on MRI. Diagnosis rests on diagnostic vitrectomy showing malignant lymphoid cells, with a vitreal IL-10 to IL-6 ratio above 1 supporting lymphoma over inflammation. Serologies and Quantiferon evaluate infectious uveitides, which would not produce sub-RPE lymphomatous infiltrates or steroid-refractory behavior in this pattern.

Reference: Kanski's Clinical Ophthalmology, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.