Abstract
Marginal zone lymphoma (MZL) is an indolent lymphoma that rarely involves the central nervous system (CNS). Clonal B-cell lymphomatosis of marginal zone origin (CBL-MZ) is a premalignant condition referring to the presence of clonal B cells in the peripheral blood without evidence of organomegaly, lymphadenopathy or other features of established lymphoma, which may uncommonly progress to MZL, and as such does not require treatment beyond active surveillance. A 54-year-old male with previously diagnosed CBL-MZ presented with multiple recurrent subcortical ischaemic strokes. There was no evidence of progression to overt MZL or secondary transformation on repeated evaluation. His strokes proved refractory to antithrombotic therapy and anticoagulation. The absence of significant cardiovascular risk factors led to an extensive evaluation which excluded secondary causes such as cardioembolism, prothrombotic state or systemic vasculitis. Eventually, he was found to have lymphomatous involvement of the cerebrospinal fluid. The recurrent ischaemic strokes were attributed to a cerebral small vessel vasculopathy from neoplastic meningitis, which prompted the initiation of chemotherapy, leading to a remarkable cessation of stroke recurrence. This case highlights the importance of considering CNS involvement even in indolent or premalignant lymphomas when these patients present with "cryptogenic" recurrent strokes that appear refractory to standard secondary stroke prevention therapy. We also describe the approach to recurrent ischaemic stroke, the importance of imaging to determine the stroke mechanism, and the approach to small vessel cerebral arteriopathies.