Crystal Arthropathies

The answer first

Crystal arthropathies are inflammatory joint diseases caused by deposition of microcrystals — monosodium urate (gout), calcium pyrophosphate (CPPD disease, including "pseudogout"), and rarely basic calcium phosphate (hydroxyapatite) or calcium oxalate. The FRACP candidate must defend the gold-standard diagnosis of gout (polarised-light microscopy of synovial fluid showing negatively birefringent needle-shaped monosodium urate crystals), the serum urate target on urate-lowering therapy (less than 360 micromol/L or 6 mg/dL; less than 300 micromol/L or 5 mg/dL for tophaceous gout), and the indications for urate-lowering therapy (two or more attacks per year, tophi, urate arthropathy, urolithiasis). ^{[1] [8]}

The answer-first synthesis is: confirm crystal deposition by synovial fluid analysis whenever feasible (do not diagnose gout on hyperuricaemia alone), terminate the acute attack with anti-inflammatory therapy (NSAID, colchicine, or glucocorticoid), and institute urate-lowering therapy with allopurinol first-line, started during the acute attack under anti-inflammatory cover, with a treat-to-target serum urate strategy. ^{[7] [10]}

References12ShowHide

1. [1]Vargas-Santos AB, Taylor WJ, Neogi T Gout Classification Criteria: Update and Implications Current rheumatology reports, 2016.PMID 27342957
2. [2]Janssens HJEM, Fransen J, Janssen M et al. Performance of the 2015 ACR-EULAR classification criteria for gout in a primary care population presenting with monoarthritis Rheumatology (Oxford, England), 2017.PMID 28431109
3. [3]Pascart T, Filippou G, Lioté F et al. Calcium pyrophosphate deposition disease The Lancet. Rheumatology, 2024.PMID 39089298
4. [4]Stack J, McCarthy G Calcium pyrophosphate deposition (CPPD) disease - Treatment options Best practice & research. Clinical rheumatology, 2021.PMID 34756508
5. [5]Abhishek A, Tedeschi SK, Pascart T et al. The 2023 ACR/EULAR Classification Criteria for Calcium Pyrophosphate Deposition Disease Arthritis & rheumatology (Hoboken, N.J.), 2023.PMID 37494275
6. [6]Zhang W, Doherty M, Pascual E et al. EULAR recommendations for calcium pyrophosphate deposition. Part II: management Annals of the rheumatic diseases, 2011.PMID 21257614
7. [7]Richette P, Doherty M, Pascual E et al. 2016 updated EULAR evidence-based recommendations for the management of gout Annals of the rheumatic diseases, 2017.PMID 27457514
8. [8]Hainer BL, Matheson E, Wilkes RT Diagnosis, treatment, and prevention of gout American family physician, 2014.PMID 25591183
9. [9]Mackenzie IS, Ford I, Nuki G et al. Long-term cardiovascular safety of febuxostat compared with allopurinol in patients with gout (FAST): a multicentre, prospective, randomised, open-label, non-inferiority trial Lancet (London, England), 2020.PMID 33181081
10. [10]Clebak KT, Morrison A, Croad JR Gout: Rapid Evidence Review American family physician, 2020.PMID 33118789
11. [11]Yuan JSJ, Shashidhara A, Sutaria A et al. An update on the pharmacotherapy of gout Expert opinion on pharmacotherapy, 2025.PMID 39665289
12. [12]White WB, Saag KG, Becker MA et al. Cardiovascular Safety of Febuxostat or Allopurinol in Patients with Gout N Engl J Med, 2018.PMID 29527974