Gout Flashcards
What is gout?
Inflammatory crystal arthropathy caused by precipitation + deposition of uric acid crystals in synovial fluid + tissues
What is the broad cause of gout?
Hyperuricaemia
Decreased uric acid excretion (90%)
or
Increased production (10%)
List 3 causes of decreased uric acid excretion
Drugs
CKD
Lead nephropathy
List 4 drugs that decrease uric acid excretion
Aspirin
Thiazide diuretics
Loop diuretics
Pyrazinamide
List 3 causes of increased uric acid production
High cell turnover
Enzyme defects
Diet rich in protein (esp. purine)
List 4 causes of high cell turnover that can increase uric acid production
Tumor lysis syndrome
Myeloproliferative/ lymphoproliferative disorders
Psoriasis
Chemo/ Radiation
Name a syndrome with enzyme defects causing increased uric acid production
Lesch-Nyhan syndrome
X-linked recessive (only seen in boys)
Hypoxanthine-guanine phosphoribosyl transferase (HGPRTase) deficiency
List 5 features of Lesch-Nyhan syndrome
Gout
Renal failure
Neurological deficits
Self-mutilating behaviour
Learning difficulties
List 4 types of food rich in purines
Meat (Liver, Kidneys)
Seafood
Oily fish (Mackerel, sardines)
Yeast products
What can cause combined decreased excretion and overproduction of uric acid predisposing to gout?
High alcohol consumption esp. beer
How does weight impact levels of uric acid?
Higher BMI correlates with higher uric acid levels, regardless of dietary habits.
Describe onset of episodes of gout
Acute
Typically max. intensity within 12h
Give 3 S/S of gout
Pain +++
Swelling
Erythema
What is the most common joint in first presentation of gout?
1st metatarsophalangeal (MTP)
~70%
= Podagra
Why are peripheral small joints in the lower extremities especially affected in gout?
Tissue temperature within them is physiologically lower, which promotes uric acid deposition.
List 3 other commonly affected joints in gout
Ankle
Wrist
Knee
What does chronic gouty arthritis lead to?
Tophi formation
Painless hard nodules with possible joint deformities
May appear yellow/ white because of overlying attenuated skin
Where may bone tophi be seen?
Elbows
Knees
Extensor surfaces of forearms
Where may soft tissue tophi be seen?
Pinna of external ear
Achilles tendon
Olecranon bursa
What is the gold standard investigation for suspected gout?
Arthrocentesis + synovial fluid analysis
What is seen on synovial fluid analysis in gout?
Needle shaped negatively birefringent monosodium urate crystals under polarised light
When should uric acid be measured in gout? What result supports diagnosis?
Acutely: Uric acid >,360 umol/L
If <360, repeat once acute episode has settled (~2w later)
Why must serum uric acid levels be interpreted with caution?
Not always raised in acute gouty arthritis
List 4 radiological features of gout
Joint effusion (early)
Well-defined punched out erosions with sclerotic margins in a juxta-articular distribution
Eccentric erosions
Soft tissue tophi
What are the punched-out lytic bone lesions in gout also known as?
Rat-bite erosions
Describe first line management of acute gout
NSAID at max dose e.g. Naproxen continued until 1-2 days after attack resolved + PPI
or
Colchicine
or
Prednisolone 30-35mg OD for 5 days
+
Continue allopurinol if taking already
What are 2 unfavourable features of colchicine use in acute gout?
Slower onset of action (than NSAIDs)
SE: Diarrhoea
How should colchicine be used in those with renal impairment?
Use with caution
Reduce dose if eGFR is 10-50 ml/min
Avoid if eGFR < 10 ml/min
What is an alternate treatment of acute gout if colchicine and NSAIDs are contraindicated?
Intra-articular/ IM steroid injection
In which patients should urate lowering therapy be offered?
All patients after their first attack of gout
Give 5 indications where urate lowering therapy is particularly recommended
> ,2 attacks in 12 months
Tophi
Renal disease
Uric acid renal stones
Prophylaxis if on cytotoxics/ diuretics
When should urate lowering therapy be started?
Once inflammation has settled as ULT is better discussed when patient is not in pain
Why should anti-inflammatories be given during acute gout and for at least 1w before ULT?
XOIs during acute flare may exacerbate Sx by mobilising urate crystals
What is the first line agent in urate lowering therapy? What is the MOA?
Allopurinol 100mg OD with dose titrated every few weeks to aim for a serum uric acid of < 360 µmol/l
Xanthine Oxidase inhibitor
In which patients should the starting dose of allopurinol be reduced?
Reduced eGFR
What additional drug should be considered alongside initiation of allopurinol?
Colchicine cover
(NSAIDs if colchicine not tolerated)
May need to be continued for 6 months
What is the second line agent in urate lowering therapy? What is the MOA? When is this indicated?
Febuxostat
Xanthine Oxidase inhibitor
When allopurinol is not tolerated/ is ineffective
Name a drug that can be used in refractory cases for urate lowering therapy
Pegloticase
Uricase (Urate oxidase) enzyme that catalyses degradation of urate
List 3 lifestyle modifications for management of gout
Reduce alcohol + avoid during acute attack
Lose weight if obese
Avoid food high in purines
Which drug may be suitable for patients with gout and co-existing hypertension?
Losartan
Has specific uricosuric action
How does vitamin C intake affect serum uric acid levels?
Increased Vitamin C intake decreases uric acid levels
