Central nervous system relapse with optic nerve infiltration and meningeal involvement in B-cell acute lymphoblastic leukemia

Leukemic infiltration of the optic nerves is an uncommon yet clinically significant manifestation of central nervous system (CNS) involvement in acute lymphoblastic leukemia (ALL). We report an adult male with B-cell ALL who developed progressive bilateral visual loss due to optic nerve infiltration and meningeal involvement, representing CNS relapse. The patient had been previously diagnosed with B-cell ALL and had discontinued therapy after induction chemotherapy. Several months later, he presented with bilateral visual loss and pain on eye movements. Ophthalmologic examination revealed bilateral optic disc edema. Magnetic resonance imaging of the brain and orbits demonstrated bilateral optic nerve thickening with postcontrast enhancement and associated leptomeningeal enhancement. Cerebrospinal fluid analysis confirmed malignant lymphoid cells, establishing CNS relapse. The patient was restarted on CNSdirected chemotherapy with partial visual improvement. This case highlights the optic nerve as a pharmacologic sanctuary site, emphasizes the importance of dedicated orbital imaging in patients with suspected CNS leukemia, and underscores the need for strict treatment compliance and long-term surveillance in ALL.