Isolated CNS Blast Crises in Chronic Myeloid Leukaemia Presenting as Hypertrophic Pachymeningitis and Bilateral Optic Neuritis: A Case Report.

Extramedullary blast crises of Chronic Myeloid Leukaemia (CML) involving CNS is rare and usually accompanies systemic relapse. Isolated CNS blast relapse is an extremely uncommon event. A 35-year-old male was diagnosed with chronic phase (CP) CML two years back at our hospital and was started on imatinib 400 mg daily. Patient achieved haematological and cytogenetic remission at three and 12 months respectively but was non-compliant with medications thereafter. He presented to our emergency with headache and bilateral visual loss. CNS examination revealed neck rigidity and fundoscopy revealed disc edema with retinal vein dilatation and haemorrhages. Cerebrospinal fluid (CSF) analysis revealed lymphocytic pleocytosis and a positive cytospin for myeloid blasts. MRI brain suggested pachymeningeal enhancement involving falx cerebri and tentorium along with bilateral optic nerve thickening. Patient maintained cytogenetic remission at current presentation. A diagnosis of isolated CNS blast crises with pachymeningitis and bilateral optic nerve involvement was made and two doses of intrathecal chemotherapy were administered. However, patient died due to a rapidly downhill course. A previously unreported finding of pachymeningitis with bilateral optic neuritis has been highlighted in this case, along with a brief review of this rare condition.