Gout and pseudogout Flashcards
What is gout?
Gout is an inflammatory arthritis caused be deposition of monsodium urate crystals within joints, most commonly the first metatarsophalangeal joint.
Risk factors for gout
Uric acid overproduction
- Increased cell turnover: such as haematological malignancies
- Cytotoxic drugs: chemotherapeutic agents cause increased cell death
- Purine rich diet: particularly meat, seafood and alcohol
- Obesity
- Lesch-Nyhan syndrome
- Sever psoriasis
Reduced excretion of uric acid
- Chronic kidney disease
- Diuretics: thiazide and loop diuretics
- Pyrazinamide
- Lead toxicity
Clinical features of gout
Relapsing and remitting course. Symptoms last 7-10 days. Patients are asymptomatic between flares.
Symptoms:
- Rapid onset severe joint pain
- Joint stiffness
Signs:
- Joint inflammation: tenderness, erythema and swelling
- Monoarticular or oligoarticular (≤ 4 joints)
- 1st MTP most common in first presentation (70%)
- Anke, wrist and knee commonly affected
- Gouty tophi: nodular masses of urate crystals form, usually as a late complication
In patients that present with typical gout like symptoms in the absence of other possible causes, such as septic arthritis, NICE state that no initial investigations are required. However, septic arthritis is often difficult to exclude. The following investigations may be considered:
- Joint aspiration
- Serum urate (usually taken 4-6 weeks after the attack resolves as levels may be falsely low/normal during the attack as the urate is deposited within the joint)
- Joint X-ray (may be normal)
What is seen on the joint aspiration of someone with gout?
Needle shaped crystals with negative birefringence under polarised microscopy confirm the diagnosis.
Managment of acute flare of gout
- Anti-inflammatory
- NSAIDs or colchicine can be used first line; colchicine commonly used in renal impairment. Continue until 24-48 hours after symptoms have improved
- Co-prescribe a proton pump inhibitor
- Corticosteroids:
- Intra articular steroids may be used as a second line agent for monarticular disease
- A short course of oral steroids (usually 15mg/day) for oligoarticular disease or if NSAIDs or colchicine are contraindicated
- If patients are already on allopurinol or febuxostat, it should be continued
Medications used to prevent gout
- Allopurinol: first line and offered to all patients after resolution of their first attack; start at low dose (50-100mg/day) and increase by 100mg every 4 weeks. Lower doses required in renal impairment.
- Consider colchicine cover when staring alopurinl; may be needed for 6 months
- Febuxostat: second line if allopurinol not tolerated or ineffective
Aim of urate lowering therapy
Serum uric acid of < 300 micro mol/l
Lifestyle advice for patients with gout
- Weight loss
- Avoid alcohol
- Avoid food high in purine
What is pseudogout?
Pseudogout is a form of inflammatory arthritis caused by deposition of calcium pyrophosphate crystals in the synovium.
Which joints are most commonly affected in pseudogout?
Knee, shoulder and wrist
Risk factors for pseudogout
- Increasing age: the greatest known risk factor for pseudogout
- Previous joint trauma
- Hyperparathyroidism
- Haemachromatosis
- Acromegaly
- Wilsons disease
- Hypomagnesaemia
- Hypophophataemia
Clinical features of pseudogout
Similar to gout
Symptoms
- Rapid onset severe joint pain: knee, shoulder and wrist are commonly affected
- Joint stiffness
Signs
- Joint inflammation: pain, erythema and swelling
- Signs can be monarticular or polyarticular
Primary investigations in pseudogout
- Joint aspiration
- Joint X-ray: chondrocalcinosis (calcification of articular cartilage) is seen in 40% of cases and is highly suggestive of pseudogout but not diagnositic
Joint aspiration of patient with pseudogout
Weakly-positive birefringent rhomboid-shaped crystals under polarised microscopy confirm the diagnosis.
