Crystal arthropathy (gout, pseudogout) Flashcards
Define gout.
Disorder of uric acid metabolism causing recurrent bouts of acute arthritis caused by deposition of monosodium urate crystals in joints, and also soft tissues and kidneys.
What is the aetiology of gout?
Metabolic disturbance is hyperuricaemia which may be caused by:
- Increased urate intake or production - increased dietary intake, increased nucelic acid (purine) turnover (e.g. lymphoma, leukaemia, polycythaemia vera, psoriasis) or rarely caused by increased synthesis (e.g. Lesch-Nyhan syndrome)
- Decreased renal excretion - idiopathic, drugs (e.g. “CANT LEAP”), renal dysfunction
Which drugs can cause decreased renal excretion of uric acid?
CANT LEAP
- ciclosporin
- alcohol
- nicotinic acid
- thiazides
- loop diuretics
- ethambutol
- aspirin
- pyrizinamide
How common is gout?
- Prevalence 0.2%
- M:F 10:1 ratio
- Rare in pre-puberty and in pre-menopausal womrn
- More common in higher social classes
What is the typical presentation of and acute attack of gout?
Acute attack -
- May be precipitated by trauma, infection, alcohol, starvation, introduction or withdrawal pf hypouricaemic agents.
- Suddent excruciating monoarticular pain, usually of metatarsophalangeal joint of the great toe.
- Symptoms peak at 24 hours and resolve in 7-10days.
- Occassionally acute attacks present with cellulitis, polyarticular or periacrticular involvement.
- Attacks are often recurrent, but the patient is symptom free between attacks.
What are the three types of presentations of gout?
- Acute attack
- Intercritical gout
- Chronic tophaceous gout
- Urate urolithiasis (renal calculi)
What is the typical presentation of intercritical gout?
Asymptomatic period between acute attacks
What is the typical presentation of chronic tophaceous gout?
- Follows repeated acute attacks
- Persistent low-grade fever
- Polyarticular pain with painful tophi (urate deposits)
- Best seen on tendons and the pinna of the ear
What are the signs of gout on examination?
- rapid-onset severe pain
- joint stiffness
- foot joint distribution
- few affected joints
- swelling and joint effusion
- tenderness
- tophi
Common
- erythema and warmth
What investigations would you do for gout?
- Synovial fluid aspirate - diagnosis depends on the presence of monosodium urate crystals which are needle-shaped and negatively birefingent under polarised light. Microscopy and culture (to exclude septic arthritis)
Bloods:
- FBC - raised WCC
- U&E
- Urate - raised (but normal in acute gout). Should be obtained 2 weeks after acute attack resolves. >416 micromol/L (7 mg/dL) in men; >360 micromol/L (6 mg/dL) in women.
- ESR - raised
Imaging:
- AXR/KUB -uric acid renal stones are often radiolucent (i.e. not visible)
What lifestyle measures can you take to reduce gout?
Reduce meat and alcohol intake
How do you manage gout? (not required)
Attack - NSAID/colchicine + intra-articular corticosteroids + intramuscular ACTH if difficult to control
Surgery - if large or ulcerating tophus
Prophylaxis - allopurinol (xanthine oxidase inhibitor) or long term colchicine (risk of neuromyopathy), probenecid or sulfinpyrazon (uricosurics). Encourage high fluid intake to lower risk of renal calculi.
Define pseudogout.
Arthritis associated with deposition of calcium pyrophosphate dihydrate (CPPD) crystals in joint cartilage.
List some risk factors for gout.
- older age
- male sex
- menopausal status
- consumption of meat, seafood, alcohol
- use of diuretics
- use of ciclosporin (cyclosporine) or tacrolimus
- use of pyrazinamide
- use of aspirin
- genetic susceptibility
- high cell turnover state
weak:
- adiposity and insulin resistance
- hypertension
- renal insufficiency
- diabetes mellitus
- hyperlipidaemia
What is the aetiology of pseudogout?
- CPPD crystal formation is initiated in cartilage located near the surface of chondrocytes.
- The disorder is associated with excessive cartilage pyrophosphate production leading to local calcium pyrophosphate supersaturation and CPPD crystal formation/deposition.
- Shedding of crystals into the joint cavity precipitates acute arthritis.
What conditions/situations predispose to pseudogout?
- Most causes of joint damage predispose to pseudogout (e.g. osteoarthritis, trauma).
- More rarely, conditions such as haemochromatosis, hyperparathyroidism, hypomagnesaemia, hypophosphatasia can predispose to pseudogout.
- Familial cases and associations with metabolic diseases have been described.
- Provoking factors: Intercurrent illness, surgery, local trauma.
How common is pseudogout/calcium pyrophosphate deposition?
- Male:female ratio is 2:1
- More common in elderly (>60yrs) but can occur in younger people with associated metabolic conditions
What are the two presentation of pseudogout?
- Acute arthritis
- Chronic arthropathy
Uncommon presentations - tendonitis (e.g. achilles), tensynovitis (tendon of hand), bursitis (e.g. olecranon bursitis)
Descirbe the presentations of acute and chronic pseudogout.
Acute arthritis - painful swollen joint (e.g. knee, ankle, shoulder, elbow, wrist)
Chronic arthropathy - pain, stiffness, functional impairment
What are the signs of pseudogout on examination?
Acute arthritis -
- red,
- hot,
- tender,
- restricted movement range,
- fever
Chronic arthropathy (similar to osteoarthritis) -
- bony swelling,
- crepitus,
- deformity e.g. varus in knees,
- restriction of movement
What investgations would you do for pseudogout?
Bloods:
- FBC - high WCC in acute attack
- ESR - raised
- Blood culture - excludes infective arthritis
Joint aspiration
- Microscopy - rhomboid brick shaped crystals with peak positive birefringence under polarised light.
- Culture or gram staining - to exclude infective arthritis
Imaging:
- Xray of joint - chondrocalcinosis (linear calcification of cartilage) or signs of osteoarthritis.
What are the signs of osteoarthritis on X ray ?
- loss of joint space
- osteophytes
- subchondral cysts
- sclerosis
What are the signs of pseudogout on X ray?
Chondrocalcinosis (linear calcification)
How do you manage pesudogout (not required) ?
Acute - aspiration + intra-articular steroids + NSAIDs/colchicine
Chronic - similar to osteoarthriris (e.g. lose weight, walking aids, physio, analgesia). Oral daily colchicine if >3 attacks/year.
Surgery if severe
What is the difference between gout and pseudogout?
