Crystalline Arthropathies¶
Thomas Horton
Gout¶
Presentation¶
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Red, hot, swollen joint (classically affects 1st metatarsal phalangeal joint [podagra])
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May progress to involve ankles, knees, elbows, and small joints of hand if untreated
- Flares may also become polyarticular over time
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Gout is diagnosed with combination of clinical presentation and arthrocentesis results
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Lifestyle factors:
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Protective: Low fat dairy, hydration, weight loss, smoking cessation
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Promoting: Meat, seafood, alcohol, high fructose corn syrup, medications that lead to hyperuricemia (ex: thiazides)
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Evaluation¶
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Synovial Fluid Analysis:
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Cell count and differential: WBC 20,000-100,000, > 50% neutrophils
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Order gram stain/culture (It is possible to have septic arthritis and gout)
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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
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Imaging: generally unnecessary
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MSK ultrasound: "Double contour sign" (hyperechoic band = urate crystals deposits)
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Radiographs: Punched out erosions or lytic areas with overhanging edges
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Dual energy CT scan: gout crystal aggregates appear green. Not routinely necessary; Do not order without rheumatology consult
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Management¶
Acute:
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Do not discontinue allopurinol during an acute gout attack
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NSAIDs (if not contraindicated): Short course (2-5 days) at full anti-inflammatory dose: ibuprofen 800 mg TID, indomethacin 50 mg TID, naproxen 500 mg BID
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Colchicine (avoid if GFR \<10 mL/min. Dose reduce by 50% if GFR \<50 mL/min)
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Best if used within the first 36 hours of an attack. Much less effective if started later.
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Dosing: 1.2 mg then 0.6 mg one hour later, then 0.6 mg daily until clinical improvement
- Note drug interactions that may require dose adjustment of colchicine: Statins, diltiazem, fluconazole, cyclosporine, tacrolimus, clarithromycin, etc.
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Steroids:
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Ideally intra-articular if single joint affected and infection has been ruled out
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Oral prednisone, dose 0.5mg/kg/day until clinical improvement then taper over 7-14 days
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Anakinra (IL-1 receptor antagonist): 100mg once daily for three days (or QOD for CrCl \<30). Requires rheumatology consult. For patients with contraindications to all other treatments
Chronic:¶
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Urate Lowering Therapy (ULT)
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Indications: Strong: >2 attacks/year, one or more subcutaneous tophi, radiologic changes. Conditional: CKD 3 or worse, urolithiasis, serum urate >9
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Goal serum urate: \<6.0 mg/dL, or \<5.0 mg/dL in patients with tophi
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ULT can precipitate an acute gout flare and should always be started with low-dose NSAIDs, colchicine (0.6 mg) or prednisone (5 mg daily or QOD)
- Prophylaxis should be continued for at least 6 months until uric acid is at goal and tophi have resolved
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Allopurinol (xanthine oxidase inhibitor): Start low at 100 mg per day (sometimes even 50mg daily in those with advanced CKD) and increase as needed for target uric acid \<6 (most patients will need 400-800 mg daily)
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Adjust dose monthly (3-4 weeks). In kidney dysfunction go slower.
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Titration of allopurinol ↓ both the risk of acute gout attacks and DRESS syndrome
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Genetic testing (HLA-B*5801) recommended prior to starting for pts of Asian and African descent given ↑ incidence of allopurinol hypersensitivity if + positive allele
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Febuxostat: alternative xanthine oxidase inhibitor that is metabolized by the liver for pts at risk for DRESS or SJS related to allopurinol. Black box warning for ↑ cardiovascular risk; more expensive than allopurinol
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Consider Rheumatology consult for patients with refractory serum urate levels >6.0 on XOI
Additional pearls¶
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There is a microscope in the rheumatology clinic at VUMC (TVC 2); You can page the rheumatology fellow and they are happy to help you use it
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Uric acid level is often normal during acute gout flare
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Shifts in uric acid may be the trigger of the flare: Diuresis, dietary changes, hospital stays
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Eliminating uric acid from the diet only reduces uric acid by ~1 mg/dL. Urate lowering therapy will be needed in most patients even if diet changed
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VA specific guidance:
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Colchicine is non-formulary but is easily approved
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For steroid intra-articular injections triamcinolone is the formulary option
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Pseudogout- Calcium pyrophosphate dihydrate crystal deposition disease (CPPD)¶
Presentation¶
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Red, hot, swollen joint usually in the wrists, knees, or MCP joints
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Cannot distinguish from gout based on clinical features alone. Like gout, diagnosis is based on exam and arthrocentesis
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More prevalent in the elderly populations
Evaluation
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Synovial Fluid:
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Cell count and differential: WBC 20,000 to 100,000, >50% neutrophils
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Order gram stain/culture (It is possible to have septic arthritis and CPPD)
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Examination for crystals under polarizing light microscopy
- CPPD crystals: rhomboid-shaped, weakly positively birefringent and appear blue when parallel to the polarizer
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Imaging:
- XR: chondrocalcinosis (thin calcified line present in fibrocartilage) in the joint space (easiest to see in knee and wrists)
Management¶
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Typically follows the same treatment used for acute gout attacks (see above, little evidence)
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Some patients may develop Chronic CPP Crystal Inflammatory Arthritis.
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Resembles RA in presentation
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Treatment base on symptoms and ranges from NSAIDs (1st line) to Colchicine, HCQ, and steroids. Can also use anakinra in acute cases, with consult to rheumatology
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Additional Information¶
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CPPD can be associated with other disorders: hyperparathyroidism, hemochromatosis, hypomagnesemia, hypophosphatemia, and familial hypocalciuric hypercalcemia
- Consider further workup for these conditions, especially in a younger patient.