Crystal Arthropathy

Crystalline Arthropathies – Arissa Young

Gout

Presentation

  • Red, hot, swollen joint (Classically affects 1st metatarsal phalangeal joint [podagra])
  • May evolve to involve knees, elbows, and small joints of hand if untreated
  • Flares may become polyarticular over time
  • Gout is diagnosed with combination of clinical presentation and arthrocentesis results
  • Lifestyle factors:
    • Protective: Low fat dairy, hydration
    • Promoting:  Meat, seafood, alcohol, high fructose corn syrup, medications that lead to hyperuricemia (consider discontinuing diuretics when using as antihypertensive)

 

Evaluation

  • Synovial Fluid Analysis: 
    • Order cell count and differential
      • WBC 20,000-100,000, > 50% neutrophils
    • Order gram stain/culture (It is possible to have septic arthritis and gout)
    • Examination for crystals under polarizing light microscopy: (order “Synovial Fluid Eval” so the lab knows to look for crystals)
      • Monosodium urate crystals: needle-shaped and negatively birefringent and appear yellow when parallel to the polarizer
  • Imaging: generally unnecessary
    • MSK ultrasound: Double contour sign (hyperechoic band = urate crystals deposits)
    • Dual energy CT scan: gout crystal aggregates appear green
      • Not routinely necessary; Do not order without rheumatology consult

 

Management

Acute:

  • Do not discontinue allopurinol during an acute gout attack
  • NSAIDs (if not contraindicated):
    • Short course of any at full anti-inflammatory dose: ibuprofen 800 mg TID, indomethacin 50 mg TID, naproxen 500 mg BID
  • Colchicine (only for use in patients without CKD): 
    • Best if used within the first 36 hours of an attack. Much less effective if started later
    • Dosing: 1.2 mg then 0.6 mg one hour later, then 0.6 mg daily until clinical improvement
      • Important drug interactions (may require dose adjustment of colchicine): CYP3A4 inhibitors and P-glycoprotein/ABCB1 inhibitors
      • E.g. statins, diltiazem, fluconazole, cyclosporine, tacrolimus, clarithromycin
  • Steroids: Ideally intra-articular if single joint affected and infection has been ruled out
    • Oral prednisone - moderate dose 0.5mg/kg/day until clinical improvement and then taper over 7-14 days
  • Anakinra (Requires Rheumatology consult): once daily for three days
    • Reserved for patients who have contraindications to all other treatments

Chronic:

  • Urate Lowering Therapy (ULT)
    • Indications: 2-3 attacks/year, tophi, radiologic changes, gout with CKD, urolithiasis
    • Goal serum urate: <6.0 mg/dL or <5.0 mg/dL in patients with tophi
    • ULT can precipitate an acute gout flare, thus it should always be started with: low-dose NSAIDs, low-dose colchicine (0.6 mg) or low-dose prednisone (5 mg daily)
      • Prophylaxis should be continued for 3-6 months after initiation of urate-lowering therapy (Can stop once uric acid is <6 for 6 months on a constant ULT dose)
    • Allopurinol (xanthine oxidase inhibitor): Start low at 100 mg per day and increase as needed for target uric acid <6 (most patients will need 400-800 mg daily)
      • Adjust dose monthly (in kidney dysfunction go slower)
      • Can be used in patients with kidney dysfunction: 50 mg/day, then by 50 mg
      • Titration of allopurinol both the risk of acute gout attacks and DRESS syndrome
      • Genetic testing (HLA-B*5801) recommended prior to starting for pts of Asian and African descent given incidence of DRESS among pts with positive allel
    • Febuxostat: alternative xanthine oxidase inhibitor that is metabolized by the liver for pts at risk for or with a history of DRESS or SJS related to allopurinol
      • Has black box warning for cardiovascular risk; more expensive than allopurinol

 

Additional Information

  • VUMC guidance: there is a microscope in the rheumatology clinic (TVC 2);  You can page the rheumatology fellow and they are happy to help you use it
  • VA specific guidance:
    • Dr. Birchmore is excellent at teaching residents how to use the polarizing microscope
    • Colchicine is non-formulary but is easily approved
    • For steroid intra-articular injections triamcinolone is the formulary option
  • Uric acid level is often normal during acute gout flare
  • Shifts in uric acid may be the trigger of the flare: Diuresis, dietary changes, hospital stays
  • Eliminating uric acid from the diet will only reduce uric acid by ~1 mg/dL, so urate lowering therapy will be needed in most patients even if diet changed

 

 

Pseudogout

Presentation

  • Red, hot, swollen joint usually in the wrists, knees, or MCP joints
  • Cannot distinguish from gout based on clinical features alone
  • Like gout, diagnosis is based on exam and arthrocentesis

 

Evaluation

  • Synovial Fluid:
    • Order cell count and differential
    • WBC 20,000 to 100,000, >50% neutrophils
  • Order gram stain/culture (It is possible to have septic arthritis and CPPD)
  • Examination for crystals under polarizing light microscopy
  • CPPD crystals: rhomboid-shaped, weakly positively birefringent and appear blue when parallel to the polarizer
  • Imaging: 
    • XR: chondrocalcinosis in knee and wrists (thin calcified line present in fibrocartilage)

 

Management

Typically follows the same treatment used for acute gout attacks (see above, little evidence)