Metastatic Neuroblastoma Presenting as Suspected Septic Arthritis: A Case Report

Neuroblastoma is the most common extracranial solid malignancy in childhood and can present with a wide range of clinical manifestations.Although metastatic disease frequently involves the bone and bone marrow, musculoskeletal symptoms may mimic common orthopedic conditions, resulting in diagnostic delays.We report a case of a previously healthy two-year-old boy who presented with a three-week history of bilateral lower limb pain, limping, intermittent fever, and abdominal pain.Initial evaluation raised suspicion for septic arthritis due to elevated inflammatory markers and magnetic resonance imaging (MRI) findings suggestive of hip infection.Hip aspiration yielded turbid inflammatory fluid containing numerous pus cells.However, cultures remained sterile, and the patient showed persistent symptoms despite broadspectrum antimicrobial therapy.Further evaluation with whole-body MRI revealed diffuse bone marrow signal abnormalities involving the axial and appendicular skeleton, together with a right suprarenal mass, findings highly suspicious for metastatic neuroblastoma.Subsequent positron emission tomography/computed tomography performed at an external institution demonstrated widespread skeletal involvement, further supporting the suspicion of metastatic neuroblastoma.Tissue diagnosis was not obtained at our institution because the family elected to pursue further evaluation and treatment abroad.This case highlights the importance of reconsidering the diagnosis in children with presumed musculoskeletal infection who fail to improve as expected.Persistent fever, sterile cultures, anemia, elevated inflammatory markers, and multifocal musculoskeletal symptoms should prompt consideration of malignancy and early multidisciplinary evaluation.