Synovial sarcoma masquerading as juvenile idiopathic arthritis

Area of Science:

• Pediatric Oncology
• Rheumatology
• Musculoskeletal Oncology

Background:

• Chronic monoarthritis in early adolescents requires careful differential diagnosis.
• Misdiagnosis can delay appropriate treatment for rare and aggressive conditions.

Observation:

• A patient presented with deforming monoarthritis, initially treated for skeletal tuberculosis and later suspected juvenile idiopathic arthritis.
• Clinical deterioration with severe knee arthritis and calf swelling prompted further investigation.

Findings:

• Imaging revealed synovitis with necrotising myositis.
• Histopathology confirmed synovial sarcoma with skeletal and pulmonary metastasis.

Implications:

• This case underscores the importance of considering rare malignancies in pediatric arthritis presentations.
• Timely and accurate diagnosis is critical for managing aggressive pediatric sarcomas, though prognosis remains challenging.