Misdiagnosed as Ankylosing Spondylitis: An Unusual Case of Acute Promyelocytic Leukemia with Myeloid Sarcoma

Introduction:Acute promyelocytic leukemia (APL) accounts for 7-8% of adult acute myeloid leukemia cases. Extramedullary manifestations in APL are rare at initial diagnosis and exhibit unique biological characteristics. Case presentation: This study aimed to report a unique case of a 31-year-old male who initially presented with lower back pain and was misdiagnosed with Ankylosing Spondylitis. Subsequent development of cervical lymphadenopathy led to further investigation, revealing myeloid sarcoma and APL with Promyelocytic Leukemia/Retinoic Acid Receptor Alpha translocation. The patient underwent standard all-trans-retinoic acid therapy, followed by consolidation chemotherapy. Despite a relapse, the patient achieved complete remission after treatment with arsenic trioxide and a bone marrow transplant, which is uncommon for APL patients. Conclusion: This case underscores the importance of considering hematologic malignancies in patients with atypical presentations and highlights the role of genetic testing in confirming diagnoses. The successful use of a bone marrow transplant in this case suggests potential benefits for selected APL patients with extramedullary involvement and relapse.