Extramedullary Relapse of Acute B-Lymphoblastic Leukemia Leading to Paraplegia in a Child with Down Syndrome.

Background: Acute B-lymphoblastic leukemia (B-ALL) is a common malignancy in children. Patients with Trisomy 21 (Down syndrome) are at a higher risk of developing hematologic disorders. Despite advances in treatment, extramedullary relapse remains a challenge, particularly when it manifests as spinal cord compression leading to paraplegia, a rare but severe complication.

Methods: We describe the clinical course of an 11-year-old male with Trisomy 21, diagnosed with B-ALL. The patient was treated with standard chemotherapy (VDLP regimen) followed by central nervous system prophylaxis through lumbar puncture and intrathecal chemotherapy. Despite achieving minimal residual disease (MRD)-negative status, the patient developed progressive lower back pain and acute paraplegia. Imaging studies and subsequent spinal surgery were performed to diagnose and manage the spinal cord lesion.

Results: The patient's spinal pathology confirmed a relapse of B-ALL with extramedullary involvement. Immunohistochemistry of the tumor showed markers consistent with B-lymphoblastic leukemia/lymphoma. Chemotherapy-induced remission was initially achieved, but the patient experienced bone marrow suppression after each cycle, leading to further hospitalization and supportive treatments. Postsurgical findings showed no CNS involve-ment, and bone marrow MRD remained negative.

Conclusions: This case highlights the complexity of managing B-ALL in children with Trisomy 21, who may be prone to extramedullary relapse despite systemic remission. Early recognition of spinal symptoms and prompt surgical intervention are critical in preventing irreversible neurological damage such as paraplegia. This case underscores the need for vigilant monitoring and tailored therapeutic strategies in high-risk populations.