Gout Flashcards
What crystal is deposited in gout?
Monosodium urate (MSU)
What causes gout? What is the threshold that defines this?
Hyperuricaemia
Urate > 0.41 mmol/L
What is the source of urate?
Degradation product of purines:
- cell turnover
- dietary intake
- de novo synthesis
What joints are most commonly affected?
Metatarsophalangeal joint
Mid-foot
Knee
Less commonly can cause oligo/polyarthropathy
Clinical presentation:
- time course
- symptoms
- acute onset, lasting 7-10 days before spontaneous resolution (if no treatment used)
- Intensely painful arthropathy
What are gouty tophi? Why to they form and what made from?
Nodules consisting of MSU crystals and chronic granulomatous inflammatory tissue
What is the prevalence of gout?
What countries have particularly high rates of gout?
2.7 - 6.7% in countries with a western lifestyle
Taiwan and Maori people
What are the risk factors for Gout?
Hyperuricaemic and the things that cause it:
- increased production: high cell turnover (psoriasis, myeloproliferative disorders)
- High dietary intake: (alcohol), (fructose), beer, meats, seafood
- Reduced excretion: CKD, metabolic syndrome, diuretic use
Other than hyperuricaemia, what other factors predispose to gout?
Joint trauma, medical illness, surgery, dehydration, advancing age, male sex
What proportion of people with hyperuricaemia develop gout?
The minority of people with hyperuricaemia develop gout - it is necessary but not sufficient.
Do dietary or genetic effects have a greater impact on hyperuricaemia?
Genetic
What are the steps in pathophysiology of gout?
- Hyperuricaemia
- Crystal formation (reduced solubility, nucleation, crystal growth)
- Crystals interact with macrophages to activate NLRP3 inflammasome resulting in release of IL-1beta and inflammatory infiltration along with cardinal signs
- Resolution when dying neutrophils result in NETs, sequestration of pro-inflammatory cytokines
What are the microscopy findings consistent with gout?
negative birefringent, needle-shaped crystals
Typical clinical manifestations
Atypical clinical manifestations
- acute episodes involving joint structures, asymmetric, self-limiting
- development of tophi without flares (people taking corticosteroids), multiple joints involved (more common with chronic hyperuricaemia), persistent symptoms (not self-limiting), proximal large joints
Diagnosis
Gold-standard is microscopy based
classification criteria based diagnosis is less accurate
Differential diagnoses
- CCP crystal arthropathy
- psoriatic arthritis
- reactive arthritis
- Lyme disease
- septic arthritis
What imaging can be useful in the diagnosis of gout?
- Ultrasonography - “double-contour” sign
2. Dual energy CT
Is uric acid always elevated during a gout flare?
No, can be normal, especially in post-surgical flares
Consider rechecking after resolution of flare.
What effect does bariatric surgery have on uric acid levels in the obese?
reduces serum levels
reduces incidence of gout by 34%
Management:
1. Gout flares
1. NSAIDs (naproxen 500mg BD), colchicine (1mg followed by 0.5mg 1 hour after), corticosteroids - alone or in combination, ##canakinumab (IL-1beta MAB, rarely used due to cost but it is effective) # Anakinra non-inferior to NSAIDs, colchicine, prednisolone
Management
- Urate lowering therapy
- medication classes
- practice points
- xanthine oxidase inhibitors (allopurinol, febuxostat)
- uricosuric drugs (probenecid)
- recombinant uricase (pegloticase)
-Recommended to treat to target (<0.36 mmol/L) to prevent progressive joint damage and further acute flares (consider lower target <0.3 mmol/L in tophaceous gout)
Commence if there is an established diagnosis of gout with more than one flare per year, tophi, CKD or urolithiasis
Can be safely started during a flare but start at low dose
Monitor serum urate levels
Management
3. Anti-inflammatory prophylaxis
Can be used (colchicine or low dose NSAIDs)
Management
4. Lifestyle modification
Little data, however, rheumatology guidelines recommend the following:
- weight loss, reduced intake of purine rich foods, avoidance of EtOH and fructose, low-fat dairy
Management
5. Nurse led care
Comprehensive nurse led care has been found to be superior to GP care
What are some AEs for xanthine oxidase inhibitors?
Allopurinol:
- allopurinol hypersensitivity syndrome (AHS)
- first few months post commencement, associated with HLA-B*5801 (Asian, esp. Chinese populations), CKD, concomitant diuretic use - Febuxostat
- may be associated with increased cardiovascular events
