When Relapse Wears a Different Face—Uveitis Masquerade Syndrome as the Initial Presentation of Early Relapse in IKZF1-Plus B-Cell Acute Lymphoblastic Leukemia: A Case Report with Review of Literature

Anterior chamber leukemic infiltration presenting as pseudohypopyon is an exceptionally rare manifestation of relapsed acute lymphoblastic leukemia (ALL) and may masquerade as inflammatory uveitis, delaying recognition of systemic recurrence. We report a 5-year-old boy with high-risk IKZF1-plus B-cell precursor ALL (BCP-ALL) who achieved morphological remission after induction chemotherapy and subsequently became measurable residual disease (MRD)-negative following consolidation. During the tenth cycle of maintenance therapy, he developed painless bilateral ocular redness with pseudohypopyon in the absence of inflammatory signs. Bone marrow examination showed persistent morphological remission (3% blasts); however, multiparameter flow cytometry detected MRD positivity (0.10%), indicating molecular relapse. Cerebrospinal fluid (CSF) examination demonstrated lymphoblasts, confirming concurrent central nervous system (CNS) relapse, while brain and orbital magnetic resonance imaging were unremarkable. Based on the characteristic ocular findings and confirmed systemic relapse, anterior chamber paracentesis was deferred because it would not have altered management. The patient received salvage therapy with mini-hyperfractionated cyclophosphamide, vincristine, and dexamethasone combined with inotuzumab ozogamicin and protocol-directed CNS therapy as bridging treatment to allogeneic hematopoietic stem cell transplantation. This case highlights bilateral pseudohypopyon as a rare presenting feature of molecular relapse in high-risk IKZF1-plus BCP-ALL. It emphasizes that integration of ophthalmic examination with MRD assessment and CSF evaluation can facilitate early diagnosis despite persistent morphological remission, enabling timely multidisciplinary management of leukemic ocular masquerade syndrome.