Primary central nervous system lymphoma (PCNSL) is a rare tumor that can involve the brain parenchyma, spinal cord, leptomeninges, or vitreoretinal space. A wide range of clinical and radiologic findings are described with PCNSL. Here, we present a patient with systemic lupus erythematous (SLE) who presented with acute monocular vision loss secondary to frosted branch angiitis, which was subsequently revealed to be an initial manifestation of PCNSL.

A 37-year-old woman with SLE treated with prednisone, mycophenolic acid, and hydroxychloroquine presented with acute-onset left eye monocular vision loss.  On exam, she exhibited no light perception in the left eye accompanied by a relative afferent pupillary defect. Funduscopic exam disclosed optic disc and macular edema, diffuse retinal hemorrhages, and tortuous vessels with perivascular sheathing consistent with frosted branch angiitis. There was no vitreous cellular infiltrate and anterior chamber paracentesis yielded negative CMV, HSV, and VZV PCR studies.  Serologies for HIV, syphilis, and toxoplasmosis were similarly negative. She was treated with high-dose corticosteroids without visual recovery. Three weeks later, she returned with new left arm and leg weakness and sensory loss. MRI brain demonstrated a 4 cm ring-enhancing mass of the right basal ganglia, biopsy of which confirmed a diagnosis of EBV-positive diffuse large B-cell lymphoma.  CT C/A/P and bone marrow biopsy showed no evidence of systemic lymphoma.  Treatment with high-dose methotrexate and rituximab was initiated without improvement in her vision.

Frosted branch angiitis is described in association with intraocular infections, such as CMV, HSV, VZV and toxoplasmosis, autoimmune disorders including SLE and Behcet’s disease, and lymphoproliferative diseases including leukemia and lymphoma.  To our knowledge, this is the first reported case of frosted branch angiitis heralding a diagnosis of PCNSL.  Clinicians should remain suspicious for PCNSL masquerading as unusual phenotypes, particularly in the immunocompromised population.