Gout & crystal arthropathies Flashcards
Gout
A group of conditions characterised by hyperuricaemia and uric acid (monosodium urate) crystal formation. Clinically this can cause acute gout, Tophaceous Gout, uric acid nephrolithiasis & Gouty nephropathy
Calcium pyrophosphate deposition disease (CPPD) (3)
2nd commonest form of crystal arthropathy diagnosed by rhomboid calcium pyrophosphate dihydrate crystals - weakly positively birefringent
Can cause pseudogout, destructive arthropathy or asymptomatic chondrocalcinosis
Basic calcium phosphate associated conditions (3,1,3)
hydroxyapatite, octacalcium phosphate or tricalcium crystal deposition
Include milwaukee shoulder (destructive arthropathy) , acute arthritis, acute calcific periarthritis and calcific tendonitis/bursitis
Calcium Oxalate arthritis
An unusual arthritis with bipyramidal crystals, treat with NSAIDs & colchicine as with CPPD – can present acutely or subacutely
Associated with ESRD, short bowel syndrome and thiamine or pyridoxine deficiency
Epidemiology of Gout (4)
4:1 male to female ratio - men 45yrs, women 60yrs
approx 1% of people will suffer from some gout
Incidence increases with age
Clinical Features of Gout arthritis (3)
Intially asymptomatic, then acute, self-limiting (3-10days) inflammatory monoarthritis in a small joint
70-80% have a 2nd attack within 2 years. –
Attacks become polyarticular with shorter remissions (may mimic RA)
Treatment for Gout Arthritis
Acute: high dose NSAIDs w/or w/out colchicine
>1 attack/year: allopurinol. May trigger an attack
Tophaceous Gout (4)
Occurs when tophi of uric acid crystals are deposited within a matrix of lipid subcutaneously, or in organs.
Mainly occur in long term, severe hyperuriaemia
Presents with large, whitish/chalky subcut nodules
Commonest on extensor surfaces or trauma sites
Gout associated kidney damage (3)
Urate nephropathy - minor damage due to inflammation directly due to urate crystals
Uric acid nephropathy - occurs in ill, dehydrated pts, often taking cytotoxic drugs
Acute obstructive uropathy due to uric acid stones can also occur
General risk Factors for Gout (8)
General–> male, >40yo, obese, FH, HTN, alcohol/purine rich food, kidney disease, hyperlipidaemia
Investigation for Gout – Synovial fluid
most useful and will show needle shaped crystals (negatively birefringent) - yellow when parallel, blue when perpendicular
Treatment of Hyperuricaemia - decrease production (2,4)
Allopurinol –> a xanthine oxidase inhibitor,
Risk of fatal hypersensitivity reaction (particularly if second exposure or interaction with azathioprine) and can trigger acute attacks
Use if: frequent, erosive disease, nephropathy, tophi
Other conditions which can include Calcium pyrophosphate deposition (4,3,4)
Low Mg or phosphate, haemochromatosis, wilson’s disease, hyperparathyroidism, haemosiderosis, hypothyroidism, Gout, amyloidosis, trauma, familial hypocalciuric hypercalcaemia (FHC)
How common is uric acid nephropathy/nephrolithasis?
10-25% of gout sufferers
Hyperuricaemia
A blood urate level above 7mg/dl in men and 6mg/dl in women
Causes of urate overproduction (5)
Cell lysis (necrosis, haemolysis, tumours)
Drugs (cytotoxics, warfarin),
type I glycogen storage disease or Psoriasis
Dietary purines or Alcohol
Lympho- or myelo-proliferation
Causes of urate under-secretion (5)
Drugs (alcohol, diuretics, laxatives) Lead toxicity & inherited conditions Lactic, respiratory or keto-acidosis Hypothyroidism Renal failure
Drugs which can cause gout (AACDEN)
Thiazides or Frusemide Alcohol
Low dose aspirin Ethambutol
Cyclosporin Nicotinic acid
Alcohol and gout
Commonest cause – increases ATP turnover (increased urate production)
Lactic acidosis (under secretion)
Beer has lots of purines
What causes an acute attack?
A sudden change in serum urate – either sudden formation or shedding from synovial membrane
Urate is normal in 20% if cases during an attack
Treatment of Hyperuricaemia - increase secretion
Sulphinpyrazone, benzbromarone & Probenicid - uricosuric agents but sulphinpyrazone is contraindicated in renal insufficiency
Aim to keep serum urate <6mg/dl
Podagra
Gout of the big toe – most common (50% of first attacks and 90% will have it effected at some point)
Investigation for Gout – Serum uric acid
May be normal during an acute attack but are useful to monitor hyperuricaemia (not universal)
Investigation for Gout – Radiographs (6)
Only be useful to exclude other causes in early disease but later may show tophi, swelling, Periarticular joint erosions and new periosteal bone
‘Punched out lesions’ without sclerosis or osteoporosis
Stages of Gout
Asymptomatic hyperuricaemia
Acute gout (85% monoarthritis, 15% polyarthritis)
Intercritical gout
Chronic trophaceous gout
Features of Acute gout
Mimics septic arthritis – warm, red and tender/painful
Neutrophilia
Can affect bursas as well
Resolves in 3-10days
Chronic trophaceous gout (4)
Urate crystal deposits surrounded by macrophages
Commonly - ears, olecranon, achillies, periarticular
High incidence of renal impairment
Develop 10yrs after first attack
Allopurinol (5)
a xanthine oxidase inhibitor - Risk of fatal hypersensitivity reaction - particularly if second exposure or interaction with azathioprine
Can trigger acute attacks
Careful to use in elderly with poor kidney function
Always give NSAIDs as well to begin with
Pseudogout
Due to CPPD
large joint monoarthritis with endocrine/electrolyte disturbances
Responds to same treatment a gout but underlying cause should be investigated
Risk factors for Pseudogout
Hyperparathyroidism or hypothryoidism
Haemochromatosis or wilson’s disease
Acromegaly
Low magnesium or phosphate
Features of pseudogout
Knee, wrist and shoulders most commonly effected.
Will have weakly-positively bifringent rhomboid shaped crystals
X-ray will show chondrocalcinosis
Management of Pseudogout
Aspirate joint fluid to exclude septic arthritis
NSAIDs, RICE, intra-articular steroids
When to begin allopurinol treatment
2 weeks after the end of an acute attack but always give NSAID cover (Diclofenac or other) for the start incase an acute attack is triggered. If attack occur when already started keep going with allopurinol.
