Isolated central nervous system (CNS) lymphomatoid granulomatosis (LyG) is very rare, with only 40 cases found in literature review. Here we highlight a case of primary CNS LyG confirmed on brain biopsy.

This patient is a 66-year-old male with a history of diabetes complicated by diabetic nephropathy and kidney transplant in 2018 (on mycophenolate, tacrolimus, and prednisone). He presented with one month of headaches, dizziness, and nausea/vomiting. He had recently visited family in China and initially attributed his symptoms to desynchronosis but he later realized that he in fact felt unwell days prior to traveling. His initial neurologic exam was notable for mild dysarthria, downbeat nystagmus more apparent in downward gaze, and left-sided hyperreflexia. He had otherwise intact strength, sensation, coordination, and gait. His magnetic resonance imaging (MRI) brain showed multifocal partially ring enhancing lesions in the right frontal, right temporal, and right occipital lobes, as well as the posterior medulla. Lumbar puncture was notable for positive Epstein-Barr virus (EBV) polymerase chain reaction (PCR) and cytology showed lymphocytic pleocytosis without evidence of malignancy. Computed topography (CT) chest-abdomen-pelvis was unrevealing. Biopsy of the right frontal lesion showed infiltration of predominantly small T lymphocytes with rare EBV positive B lymphocytes, compatible with LyG. His immunosuppressive regimen was tapered to augment the immune response to EBV by reducing his doses of tacrolimus and prednisone. Patient did not require further chemotherapy as he experienced a robust clinical improvement with near resolution of his prior ring enhancing lesions on serial MRIs

Lymphomatoid granulomatosis is a rare EBV-associated B-cell lymphoproliferative disorder with a predilection for the central nervous system. It is difficult to distinguish clinically and radiographically from other post-transplant lymphoproliferative disorders often requiring tissue biopsy for differentiation.