A Case of Primary Central Nervous System Lymphoma Mimicking a Demyelinating Disorder: From Steroids to Stem Cell Transplant.

Primary central nervous system lymphoma (PCNSL) is a relatively uncommon and aggressive type of brain malignancy that can achieve long-term remission if it is detected promptly and treatment is initiated on time. However, it can be notorious in its presentation in atypical cases and can disguise itself as multiple other central nervous system (CNS) disorders. In this report, we describe the case of a 60-year-old immunocompetent male presenting with radiographic features, neurological deficits, and partial steroid responsiveness, which were consistent with a demyelinating disease. However, his symptomatic improvement was only transient, which prompted us to perform a biopsy. The biopsy revealed a PCNSL, and he was subsequently started on a high-dose methotrexate, rituximab, and temozolomide regimen, leading to near complete radiological remission. He underwent autologous hematopoietic stem cell transplantation post chemotherapy, which achieved durable remission with significant clinical recovery. This case highlights the risk of misdiagnosis when PCNSL presents with atypical imaging and steroid-induced improvement, while also demonstrating favourable outcomes with timely intervention with combined chemotherapy and stem cell transplantation.