Bilateral optic nerve infiltration and leukaemic retinopathy as initial signs of relapsed B cell acute lymphoblastic leukaemia with CNS and testicular involvement.

Ocular manifestations of acute lymphoblastic leukaemia (ALL) are often under-recognised, with leukaemic retinopathy and optic nerve infiltration being rare signs of relapse. We report a boy in middle childhood with relapsed B cell ALL presenting with bilateral proptosis and visual disturbances. Ophthalmic examination revealed leukaemic retinopathy and optic nerve infiltration, while neuroimaging and cerebrospinal fluid analysis documented central nervous system (CNS) involvement. Also, testicular examination and imaging found leukaemic infiltration, confirming simultaneous extramedullary relapse. Despite aggressive systemic and intrathecal chemotherapy, the prognosis was poor due to advanced disease progression. Although optic nerve infiltration alone is a recognised entity, the simultaneous occurrence of bilateral optic nerve infiltration, serous retinal detachment, and concurrent CNS and testicular relapse represents an exceptionally rare and aggressive manifestation of B cell ALL relapse. This report highlights the need for vigilant multidisciplinary surveillance of extramedullary sanctuary sites and emphasises prompt ophthalmological evaluation in ALL patients who develop visual symptoms during remission.