A 14-year-old male presents with insidious onset lower back pain and stiffness, worse in the morning and relieved by activity, bilateral sacroiliac joint tenderness on examination, and uveitis. HLAB27 is positive. Diagnosis of enthesitis-related arthritis (ERA) is considered. According to ILAR classification, ERA belongs to which JIA subtype, and what finding on MRI of sacroiliac joints would confirm active sacroiliitis?
- A ERA (spondyloarthropathy); bone marrow edema on STIR/fat-suppressed sequences ✓
- B Systemic JIA; erosions and joint space narrowing
- C Psoriatic JIA; dactylitis on plain radiograph
- D Oligoarticular JIA; ANA-positive with anterior uveitis
Correct answer: A. ERA (spondyloarthropathy); bone marrow edema on STIR/fat-suppressed sequences
Explanation
Enthesitis-related arthritis is the JIA subtype most commonly affecting adolescent males and has strong association with HLA-B27 and spondyloarthropathy features (sacroiliitis, uveitis). On MRI, active sacroiliitis is defined by bone marrow edema (subchondral/periarticular edema) detected on STIR (Short Tau Inversion Recovery) or fat-saturated T2-weighted sequences as high signal intensity, reflecting active inflammation before structural damage. Structural damage (erosions, sclerosis, ankylosis) appears later on T1 sequences and plain radiographs.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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