Gout and Crystal Arthritis Flashcards
What is the prevalence of gout in men in western dveloped countries?
3-6%
What is the prevalence of gout in women in western developed countries?
1-2%
What are the common comorbidities of gout?
obesity, HTN, CKD, diabetes
What is the main risk factor for gout?
hyperuricaemia
What defines hyperuricaemia?
serum urate > 0.405mmol/L
How is urate made?
purine catabolism results in xanthine which is converted to urate by xanthine oxidase
What causes primary urate overproduction?
accelerated purine synthesis (PRPP synthase enzyme hyperactivity)
impaired purine salvage (HGPRT1 deficiency)
hereditary defects of energy metabolism
What causes secondary urate overproduction?
Autoimmune and haemolyticanaemias
Sickle cell disease
Polycythaemiavera
Ineffective erythropoiesis (megaloblastic anaemia, thalassemia)
Myeloproliferative and lymphoproliferative disorders
Tumourlysis syndrome
What lifestyle factors cause urate overproduction?
diet and alcohol
How is urate excreted?
GI (20-30%) and renal
What causes primary underexcretion of urate?
Renal urate transporter mutations (ABCG2 loss of function and URAT1 gain of function)
What causes secondary underexcretion of urate?
CKD, diuretics, aspirin, pyrazinamide, ciclosporin, lead
What are the different clinical presentations of gout?
gout flares, subcutaneous tophi, chronic gouty arthritis
Which is the most common joint in a gout flare?
MTP1
What do you see on joint microscopy in gout?
intra-cellular needle-shaped negatively birefringent crystals
What do you see on plain film in gout?
gouty bone erosions: evidence of cortical break, overhanging edge with sclerotic margin
What is the management for a gout flare?
NSAIDs, high dose prednisolone, colchicine, steroid joint injection
What is the mechanism of action of allopurinol?
xanthine oxidase inhibitor
What is the mechanism of action of probenecid?
promotes urinary excretion of uric acid
What is the dose regime for allopurinol?
commence at 100mg daily (50mg daily if renal failure) and uptitrate by 100mg every 2-4 weeks until reach <0.36mmol/L serum urate
What is allopurinol hypersensitivity syndrome?
a reaction to allopurinol that results in desquamating rash, fever, eosinophilia, end organ damage
Which gene is associated with allopurinol hypersensitivity syndrome?
HLA B*5801
Which drugs interact with allopurinol?
azathioprine, mercaptopurine, theophylline, thiazide diuretics
Which diseases are calcium pyrophosphatase deposition disease associated with?
hypomagnesaemia, hyperparathyroidism, haemochromatosis, hypophosphataemia, OA, joint injury
