Diagnosis: Your Patient Has Pseudogout (CPPD), Not Gout
Based on the presence of rhomboid-shaped crystals under polarized light microscopy, your patient has calcium pyrophosphate deposition disease (pseudogout), not gout—regardless of the elevated uric acid level. The crystal morphology is the definitive diagnostic criterion that supersedes all other laboratory findings.
Crystal Identification: The Gold Standard
- Rhomboid crystals = pseudogout (CPPD): Calcium pyrophosphate crystals appear as rhomboid or rectangular shapes with weak positive birefringence under polarized light microscopy 1, 2
- Needle-shaped crystals = gout: Monosodium urate crystals appear as needle-shaped with strong negative birefringence—which your patient does NOT have 1, 2
- The demonstration of crystal type in synovial fluid or tissue aspirate is the gold standard for definitive diagnosis and takes precedence over all other findings including serum uric acid levels 1, 2
Why Elevated Uric Acid Doesn't Change the Diagnosis
- Elevated uric acid is common but non-specific: Approximately 15-25% of people with asymptomatic hyperuricemia never develop gout, and the specificity of hyperuricemia for diagnosing gout is relatively low 2
- Hyperuricemia can coexist with pseudogout: Your patient may have both conditions simultaneously, but the acute arthritis is caused by CPPD crystals, not urate crystals 2, 3
- Serum uric acid has limited diagnostic value: The 2020 ACR guidelines emphasize that crystal identification, not uric acid levels, establishes the diagnosis 1
Critical Pitfall to Avoid
- Do not treat with urate-lowering therapy based on elevated uric acid alone: The ACR strongly recommends against treating asymptomatic hyperuricemia, even when elevated 1, 2, 3
- Urate-lowering therapy is NOT indicated for pseudogout: Allopurinol, febuxostat, and other urate-lowering agents will not address CPPD crystal deposition and are not part of pseudogout management 1
Management Approach for Your Patient
Acute Pseudogout Attack Treatment
- First-line options: NSAIDs at maximal dose, colchicine, or intra-articular corticosteroid injection for the acute inflammatory episode 1, 4
- Systemic corticosteroids: Alternative if NSAIDs contraindicated 1
Addressing the Hyperuricemia
- Monitor but do not treat: With uric acid elevated but no evidence of gout (no MSU crystals), treatment is not indicated 1, 2, 3
- Reassess if gout develops: Only initiate urate-lowering therapy if the patient develops confirmed gout (MSU crystals) with recurrent attacks (≥2 flares per year) 1, 2
- Target <6 mg/dL if gout confirmed: If gout is eventually diagnosed separately, the treatment target would be serum uric acid <6 mg/dL using allopurinol as first-line therapy 1, 5
When Both Conditions Coexist
- Treat each condition separately: If your patient later develops confirmed gout (MSU crystals identified), manage both CPPD and gout according to their respective guidelines 1
- Crystal analysis remains essential: Any future acute arthritis episodes should undergo repeat synovial fluid aspiration to identify which crystal type is causing the flare 1, 2