B-Cell Acute Lymphoblastic Leukemia Relapse Presenting as Choroidal Infiltration Confirmed by Choroidal Biopsy Along with Ipsilateral Optic Nerve Involvement.

We report a case that describes the relapse of histopathologically confirmed B-cell acute lymphoblastic leukaemia (B-ALL) in a 21-year-old male who presented with monocular subacute vision loss, photopsia, and floaters. His exam was notable for optic disc oedema and peripapillary choroidal thickening. He underwent trans-retinal choroidal biopsy where B-ALL recurrence was confirmed, and external beam radiation was initiated. This case demonstrates how choroidal biopsy can assist with establishing the diagnosis of ALL relapse in clinically atypical cases. ALL relapse isolated to the optic nerve and choroid is rare but should be considered in patients with appropriate medical history. Prompt diagnosis and initiation of treatment can yield excellent visual recovery, prevent irreversible vision loss, and potentially avert systemic relapse.