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A 26-year-old man presents with a 9-month history of insidious-onset lower-back and buttock pain that is worse at night and on waking, with morning stiffness lasting about 90 minutes, and is relieved by exercise. He notices the pain alternating between the two buttocks. He also reports a single episode of a painful red right eye 4 months ago that resolved with eye drops from a private ophthalmologist. On examination: lumbar flexion is reduced (modified Schober increase only 3 cm); chest expansion is 2 cm; there is tenderness at both Achilles insertions; SI joint compression reproduces his back pain. He smokes 10 cigarettes per day. His father has "spine trouble". X-ray of the pelvis shows bilateral sacroiliac joint sclerosis with erosions and partial joint-space narrowing.
Questions
a) What is the most likely diagnosis, and which criteria have been satisfied? (2 marks)
Ankylosing spondylitis (radiographic axial spondyloarthritis). The modified New York (1984) criteria are satisfied: bilateral sacroiliitis (grade 2 to 3) on X-ray PLUS clinical criteria — inflammatory back pain over 3 months improving with exercise and not relieved by rest, and reduced lumbar mobility and chest expansion. The ASAS 2009 criteria for axial SpA are also satisfied (imaging arm: sacroiliitis plus multiple SpA features — uveitis, enthesitis, family history, IBP).
b) List four further investigations and the expected result. (3 marks)
- HLA-B27 — likely positive (about 90 percent sensitivity; supportive, not diagnostic).
- CRP and ESR — likely raised (but a normal value does not exclude AS).
- MRI sacroiliac joints (STIR/T2FS) — bone-marrow oedema (osteitis) of the subchondral bone (active sacroiliitis); shows active lesions even when X-ray is static.
- Rheumatoid factor and ANA — negative (seronegative spondyloarthropathy).
- Baseline CBC (anaemia of chronic disease), renal and liver function, and IGRA (Quantiferon-TB) and chest X-ray for latent TB if a biologic is being considered.
c) Outline the stepwise management. (3 marks)
- Education, smoking cessation, and daily physiotherapy (postural, mobility and breathing exercises) — non-negotiable.
- Continuous full-dose NSAID (e.g. naproxen 500 mg BD or indometacin 25 to 50 mg TDS) with a PPI — first-line; continuous dosing may slow radiographic progression.
- Local glucocorticoid injection for focal enthesitis or peripheral synovitis (NOT systemic steroids — ineffective in axial AS).
- Biologic DMARD if persistent high disease activity (ASDAS 2.1 or more or BASDAI over 4 on two occasions) — TNF inhibitor (e.g. adalimumab 40 mg SC every 2 weeks) or IL-17 inhibitor (secukinumab). Screen for TB, HBV/HCV, HIV before starting. Favour a TNFi monoclonal given his history of uveitis; avoid etanercept.
- Treat comorbidity: cardiovascular risk, osteoporosis (calcium, vitamin D), uveitis (urgent ophthalmology).
- Surgery (total hip replacement) if hip arthritis develops.
d) List four complications and one specific emergency to counsel him about. (2 marks)
- Acute anterior uveitis (already occurred — recurrent attacks cause synechiae, glaucoma, cataract).
- Aortic regurgitation and AV block.
- Apical pulmonary fibrosis (can cavitate; mimic TB).
- Secondary (AA) amyloidosis (nephrotic syndrome, renal failure).
- Cauda equina syndrome (late, from lumbar canal expansion).
- Spinal fracture after even minor trauma — the specific emergency: counsel him that his fused, osteoporotic spine fractures easily; he must seek emergency care after any fall or collision.