Isolated Myeloid Sarcoma of the Thoracic Spine as Initial Presentation of Acute Promyelocytic Leukemia: A Case Report and Literature Review

Introduction: Acute promyelocytic leukemia (APL), a subtype of acute myeloid leukemia, typically presents with severe bleeding. However, the occurrence of APL with isolated myeloid sarcoma (MS) as the sole initial presentation is extremely rare, lacking typical clinical and laboratory features, which complicates diagnosis and management. Case Presentation: A 45-year-old male was admitted for 2-month lower back pain. Spinal MRI showed T10 vertebral signal changes; histopathology confirmed the vertebral mass was myeloid origin, with PML::RARα fusion detected via PCR. Initial blood counts, coagulation tests, and bone marrow (BM) examinations were normal. However, 21 days postoperatively, the patient’s platelet count and fibrinogen level declined. A subsequent BM examination revealed abundant abnormal promyelocytes, and FISH confirmed the presence of the PML::RARα fusion gene, diagnosing APL with MS and central nervous system (CNS) involvement. He achieved complete remission with all-trans retinoic acid-based chemotherapy. Conclusion: This is a rare case of isolated thoracic vertebra promyelocytic sarcoma as the initial symptom, which later progressed to APL with MS and CNS involvement. Additionally, we performed a comprehensive literature review of 13 other cases of APL with spinal MS at the time of diagnosis. In aggregate, APL presenting with spinal MS as the sole initial manifestation is extremely rare.