Lymphomatosis cerebri masquerading as the Marburg variant of multiple sclerosis

Lymphomatosis cerebri (LC) is a rare variant of primary central nervous system lymphoma with few cases reported. Here, we describe the case of a patient with clinical presentation, imaging, and biopsy in keeping with aggressive multiple sclerosis (MS) such as that in Marburg variant. He deteriorated clinically over 9 months. Post-mortem examination yielded a diagnosis of LC with B-cell lymphoma. LC is notoriously difficult to diagnose, as it can present in various ways and biopsy of unaffected areas will be non-diagnostic. In our case, diagnosis was made more challenging by the patient's dramatic response to treatment with steroids and cyclophosphamide.