Primary leptomeningeal lymphoma masquerading as infectious tubercular meningitis.

Primary central nervous system lymphoma (PCNSL) is infrequent and often poses diagnostic conundrums due to its protean manifestations. We present the case of a South Asian young man presenting with raised intracranial pressure and a lymphocytic cerebrospinal fluid (CSF) with pronounced hypoglycorrhachia. Progression of the neuro-ophthalmic signs while on early stages of antitubercular treatment led to additional investigations that produced a final diagnosis of primary leptomeningeal lymphoma. Treatment with chemoimmunotherapy (methotrexate, cytarabine, thiotepa and rituximab (MATRix)) achieved full radiological remission followed by successful autologous transplant. This case highlights the difficulties and diagnostic dilemmas when PCNSL presents as a chronic meningeal infiltrative process. While contextually this CSF is most often indicative of central nervous system tuberculosis and justifies empirical treatment initiation alone, it is essential to include differential diagnoses in the investigation work-up, which also carry poor prognosis without timely treatment. High suspicion, multidisciplinary collaboration and appropriate CSF analysis were the key for a correct diagnosis.