Crystal Arthropathies Flashcards
What is gout?
form of inflammatory arthritis.
form of microcrystal synovitis caused by the deposition of monosodium urate monohydrate in the synovium
Natural hx of gout?
Patients typically have episodes lasting several days when their gout flares and are often symptom-free between episodes. The acute episodes typically develop maximal intensity with 12 hours
Main features gout
pain: this is often very significant
swelling
erythema
in gout Around 70% of first presentations affect which joint?
1st metatarsophalangeal (MTP) joint
What other joints can gout affect?
ankle
wrist
knee
If untreated repeated acute episodes of gout can result in
damage the joints resulting in a more chronic joint problem.
Radiological features of gout include:
joint effusion is an early sign
erosions
relative preservation of joint space until late disease
no periarticular osteopenia (in contrast to rheumatoid arthritis)
soft tissue tophi may be seen
joint space is absent in gout
false
relative preservation of joint space until late disease
Describe radiological erosions in gout
eccentric erosions
well-defined ‘punched-out’ erosions with sclerotic margins ina juxta-articular distribution, often with overhanging edges
WHat causes gout?
It is caused by chronic hyperuricaemia (uric acid > 0.45 mmol/l)
What causes Decreased excretion of uric acid
drugs*: diuretics
chronic kidney disease
lead toxicity
What causes Increased production of uric acid
myeloproliferative/lymphoproliferative disorder
cytotoxic drugs
severe psoriasis
Aspirin increases plasma urate levels
true
aspirin in a dose of 75-150mg is not thought to have a significant effect on plasma urate levels - the British Society for Rheumatology recommend it should be continued if required for cardiovascular prophylaxis
What is Lesch-Nyhan syndrome?
hypoxanthine-guanine phosphoribosyl transferase (HGPRTase) deficiency
x-linked recessive therefore only seen in boys
features: gout, renal failure, neurological deficits, learning difficulties, self-mutilation
Describe acute management of gout
NSAIDs or colchicine are first-line
oral steroids may be considered if NSAIDs and colchicine are contraindicated. A dose of prednisolone 15mg/day is usually used
another option is intra-articular steroid injection
Allopurinol should be stopped in acute flare of gout if alr taking it
false
if the patient is already taking allopurinol it should be continued
How should NSAIDs be prescribed in acute gout?
the maximum dose of NSAID should be prescribed until 1-2 days after the symptoms have settled. Gastroprotection (e.g. a proton pump inhibitor) may also be indicated
WHat is the main side effect of colchicine
diarrhoea
NSAIDs has a slower onset of action vs colchicine
colchicine has a slower onset of action.
Indications for urate-lowering therapy (ULT)
the British Society of Rheumatology Guidelines now advocate offering urate-lowering therapy to all patients after their first attack of gout
ULT is particularly recommended if: >= 2 attacks in 12 months tophi renal disease uric acid renal stones prophylaxis if on cytotoxics or diuretics
Outline urate lowering therapy
allopurinol is first-line
colchicine cover should be considered when starting allopurinol. NSAIDs can be used if colchicine cannot be tolerated.
the second-line agent when allopurinol is not tolerated or ineffective is febuxostat
in refractory cases other agents may be tried
In gout; it has traditionally been taught that urate-lowering therapy should not be started until 2 weeks after an acute attack, as starting too early may precipitate a further attack. The evidence base to support this however looks weak
true
When should ULT be commenced after an acute attack
Commencement of ULT is best delayed until inflammation has settled as ULT is better discussed when the patient is not in pain
it is better for a patient to make long-term drug decisions whilst not in pain
How should allopurinol be prescribed?
initial dose of 100 mg od, with the dose titrated every few weeks to aim for a serum uric acid of < 300 µmol/l. Lower initial doses should be given if the patient has a reduced eGFR
If prescribing colchicine or NSAIDs with allopurinol (in gout) how long should this be continued for?
The BSR guidelines suggest this may need to be continued for 6 months
What type of drug is febuxostat
xanthine oxidase inhibitor
In gout, what agents could you try in refractory cases?
uricase (urate oxidase) is an enzyme that catalyzes the conversion of urate to the degradation product allantoin. It is present in certain mammals but not humans
in patients who have persistent symptomatic and severe gout despite the adequate use of urate-lowering therapy:
Pegloticase (polyethylene glycol modified mammalian uricase) can achieve rapid control of hyperuricemia. It is given as an infusion once every two weeks
Lifestyle modifications for gout
reduce alcohol intake and avoid during an acute attack
lose weight if obese
avoid food high in purines e.g. Liver, kidneys, seafood, oily fish (mackerel, sardines) and yeast products
in gout consideration should be given to stopping precipitating drugs (such as thiazides)
true
increased vitamin C intake (either supplements or through normal diet) may increase/decrease serum uric acid levels
decrease
losartan has a specific uricosuric action and may be particularly suitable for the many patients who have coexistent hypertension
true
Diagnosis of gout?
Gout is diagnosed clinically or by aspiration of fluid from the joint.
Aspirated fluid will show:
No bacterial growth
Needle shaped crystals
Negatively birefringent of polarised light
Monosodium urate crystals
What is pseudogout?
Pseudogout is a form of microcrystal synovitis caused by the deposition of calcium pyrophosphate dihydrate crystals in the synovium.
What should you exclude in monoarthritis
Excluding septic arthritis is essential as this is a potential joint and life-threatening diagnosis.
Pseudogout is strongly associated with
increasing age
Patients who develop pseudogout at a younger age (e.g. < 60 years) usually have some underlying risk factor, such as:
haemochromatosis
hyperparathyroidism
low magnesium, low phosphate
acromegaly, Wilson’s disease
Pseudogout joint aspiration
weakly-positively birefringent rhomboid-shaped crystals
Which joints are usually affected in pseudogout?
knee, wrist and shoulders most commonly affected
X ray in pseudogout
chondrocalcinosis
in the knee this can be seen as linear calcifications of the meniscus and articular cartilage
Management pseudogout
aspiration of joint fluid, to exclude septic arthritis
NSAIDs or intra-articular, intra-muscular or oral steroids as for gout
