What is the likely diagnosis and management for a 12-year-old with migratory joint pains, cramping sensations, and chronic lower back pain, with normal X-rays and no obvious underlying conditions?

Likely Diagnosis: Juvenile Idiopathic Arthritis (JIA) or Early Axial Spondyloarthropathy

The most likely diagnosis in a 12-year-old with migratory joint pains, cramping sensations, and chronic lower back pain with normal X-rays is juvenile idiopathic arthritis (JIA), specifically the oligoarticular or enthesitis-related subtype, or early axial spondyloarthropathy (axSpA). These conditions frequently present with normal radiographs in early stages and require advanced imaging for diagnosis 1.

Key Diagnostic Features to Assess

Inflammatory vs. Mechanical Pain Characteristics

The pattern of pain is critical for distinguishing inflammatory from mechanical causes:

• Morning stiffness lasting >30 minutes that improves with activity suggests inflammatory disease 2
• Night pain, particularly in the second half of the night, is characteristic of axSpA 2
• Pain that worsens with rest and improves with exercise indicates inflammatory sacroiliitis 2
• Alternating buttock pain is a hallmark of inflammatory sacroiliitis 2
• Constant pain in a child <11 years that lasts several weeks or occurs spontaneously at night is a warning sign of serious pathology 3

Physical Examination Red Flags

• Marked stiffness and limitation of motion suggests inflammatory disease 3
• Tenderness at the thoracolumbar junction (T12-L1), one of the most common sites of spinal involvement in axial pain syndromes 4
• Positive sacroiliac joint provocative tests (≥3 positive tests provide 94% sensitivity and 78% specificity for SIJ pain) 4
• Abnormal neurological examination warrants immediate advanced imaging 5

Diagnostic Algorithm

Step 1: Laboratory Evaluation

• HLA-B27 testing is positive in 74-89% of axSpA cases and serves as an excellent screening tool in chronic back pain with onset <45 years 2, 1
• Inflammatory markers (ESR, CRP) are often elevated in inflammatory arthropathies 1
• Complete blood count to evaluate for leukocytosis suggesting infection 1

Step 2: Advanced Imaging (Essential Given Normal X-rays)

MRI is the gold standard and should be performed immediately given the clinical presentation 1, 2:

• MRI of sacroiliac joints without IV contrast (rated 8/9 by ACR) is the most appropriate initial advanced imaging 1
• Must include fat-suppressed fluid-sensitive sequences (STIR or T2-weighted fat-saturated) to detect bone marrow edema and inflammatory changes 1
• Contrast is generally not necessary for initial evaluation but may improve detection of subtle inflammatory lesions 1
• MRI of the spine should be considered if sacroiliac imaging is negative, as 6-23% of axSpA patients have isolated spine involvement 1

Ultrasound and MRI are superior to clinical examination in detecting joint inflammation and should be used for accurate assessment of extent of involvement 1.

Step 3: Specialist Referral

Urgent rheumatology referral is mandatory if inflammatory features are present 2. The mean delay in diagnosis of axSpA is 4.9-8 years, and delayed diagnosis leads to irreversible spinal ankylosis and disability 2, 1.

Differential Diagnosis Considerations

High Priority (Must Rule Out)

• Juvenile idiopathic arthritis (most common inflammatory arthropathy in children, often affects cervical spine) 1
• Axial spondyloarthropathy (can present in late childhood/adolescence) 1
• Discitis/osteomyelitis (common ages 2-12, presents with persistent night pain, low-grade fever, decreased range of motion) 1
• Spinal neoplasm (25-30% present with persistent nighttime back pain refractory to rest) 1

Lower Priority (Less Likely Given Age and Presentation)

• Spondylolysis/spondylolisthesis (typically mechanical pain pattern, activity-related) 1, 3
• Scheuermann disease (diagnosed by wedging of ≥3 successive vertebrae on radiographs) 1, 3

Management Approach

If Inflammatory Disease Confirmed

• NSAIDs are first-line treatment for axSpA, with an adequate trial defined as 3 months at maximal dose 2
• Anti-TNF biologics are indicated if NSAIDs fail and diagnosis is confirmed, as they can arrest disease progression and prevent disability 1, 2
• Physical therapy is essential for maintaining mobility 2

Monitoring

• Regular imaging follow-up (typically no more frequently than every 2 years) to monitor disease progression 6
• Serial inflammatory markers to assess treatment response 1

Critical Pitfalls to Avoid

• Do not delay MRI waiting for radiographic changes—radiographic findings lag behind clinical symptoms by 7+ years in axSpA 1
• Do not order standard spine MRI protocols designed for disc disease—specifically request sequences for inflammatory arthropathy evaluation with fat-suppressed fluid-sensitive sequences 1
• Do not dismiss migratory joint pain as "growing pains"—this pattern is characteristic of JIA 1
• Do not rely on radiographs alone—they are insensitive for early inflammatory disease and can easily miss subtle findings 1, 5
• 34% of pediatric patients with back pain have identifiable pathology, and MRI increases diagnostic yield from 8.8% (with radiographs alone) to 36% 5