Crystal arthropathies Flashcards
What is gout?
- Inflammatory arthiritis related to hyperuricaemia
Joints affected in gout
Acute gout can affect 1 or more joints but most commonly involves the 1st metatarsophalangeal joint (big toe aka podagra)
Pathophysiology of gout
Deposition of monosodium urate crystals that accumulate in joints and soft tissues, resulting:
* Acute and chronic arthirits
* Soft tissue masses called tophi
* Urate nephropathy
* Uric acid nephrolithiasis
What is common after initial flare of gout?
Second flare up occurs in 60% of patients within 1 yr and 78% within 2yrs of initial attack
Management of gout overall, non specific
- Treat acute attacks
- Prevent recurrent disease - long term reduction in uric acid levels by meds and lifestyle
Risk of gout
Associated with high risk of CVD
Risk factors of gout - non modifiable
- Age older than 40
- Male
Modifiable risk factors for gout
- Increased purine intake (urate is metabolite of purines) eg red meat and seafood
- Alcohol intake (esp beer)
- High fructose intaje
- Obesity
- Congestive HF
- Coronary artery disease
- Dyslipidaemia
- Renal disease - CKD
- Organ transplant
- HTN
- Smoking
- Diabetes mellitus
- Urate elevating medications eg thiazide and loop diuretics
Investigations for gout
Joint aspiration - rules out infection, can see crystals
Treatment gout - conservative
- Maintain optimal weight
- Regular exercise
- Diet modification - reduce purine rich foods
- Reduce alcohol consumption - beer and liqour
- Smoking cessation
- Maintain fluid intake and avoid dehydration
Appearance of gout crystals under microscope
Needle shaped crystals which are yellow - negatively birefringent through polarised light
First line pharmacological managaement for gout acutely
- NSAIDs - often naproxen
- Oral/IM steroids
- Colchicine
- Recombinant uricase - but often people have reaction to this
What scenario can we not give naproxen?
- AKI/CKD
- Bleeding/stomach ulcers
- HF
- Asthma - sometimes react
If cannot have - often have steroids
Side effects of colchicine
- GI side effects - nausea, vomitting
- Pancytopenia
- Need to decrease dose in CKD
Who do we need to take precautions giving steroids to?
- Diabetic patients - increases BMs
- HF
- Bleeding
Examination findings of someone with gout
- Hot tender joint - 1st MTP usually but cna be polyarticualr
- Tophi
How does colchicine work?
Stops neutrophils adhering to endothelium
Decreases inflammation
What are tophi?
- Depositions of urate crystals in soft tissue
- Often found in fingers and ear around helix area
- Sign of chronic gout
Long term pharmacological therapy for chronic gout
Urate lowering therapy eg allopurinol and febuxostat (F in HF or if allo not working)
These are commenced usually 2 weeks after flare up
What is intercritical gout?
Between attacks of gout - had a flare but better now
How do allopurinol and febuxostat work?
- Xanthine oxidase inhibitors
- Reduce urate formation
Less commonly used pahrmacological management of chronic gout
- Benzbromarone
- Sulfinpyrazone
- Less used as more side effects
- But these increase renal excretion of uric acid
Aim of urate lowering medications
Aim to reduce serum uric acid to less than 360 micromol/L
When should pharmacological management of acute gout be started?
Begin within 24hrs of flare up as it is highly effective then
what happens if a pt has hyperuricaemia with no symptoms?
No treatment is needed
What type of crystals are found in aspirate for gout?
Monosodium urate crystals - only in gout, diagnostic
Diagnosis of gout needs..
Joint aspiration
Differential diagnosis of gout
- Septic arthirits - monoarthiritis you should always consider
- Pseudogout
What crystals are present in pseudogout?
Calcium pyrophosphate crystals
Who does psuedogout most commonly affect?
Older women with OA
How does gout present?
- Single hot joint
Why does gout affect males more than pre-menopausal females?
Oestrogen increases excretion of uric acid in urine
Usual resolution of acute gout
- Flare up resolves within 3-10 days
- Can reoccur and spread to other joints
- Can get rebound gout if stop treatment and gout is bad again - not fully treated
Uric acid blood test results during gout
- Can be high - shows gout
- Can be low - as can be consumed when being deposited in joint spaces
- So cannot really use as a measure
Whats podagra?
Gout of 1st MTP
X-ray appearance of gout
Punched out regions at edges of joints - erosions
Sclerosis often around these lesions
Like caterpillar eating a leaf
What can we not give allopurinol alongiside and why?
- Azathioprine
- Allopurinol inhibits xanthine oxidase which breaks down azathioprine
- Can overdose on azathioprine
What can xanthine oxidase’s trigger so what must we do?
- Gout flare up - destabilses crystals as lowers serum urate so crystals break down
- Must take NSAID/colchicine for 6 months when starting these
Indications for allopurinol (long term serum urate reducing medications)
- Tophi
- Frequent attacks
- Urate caused kidney damage CKD
- Erosive joint disease
Side effect of allopurinol
- Need to decrease dose in CKD
- Rash
- Allopurinol hypersensitivity syndrome
What is allopurinol hypersensitivity syndrome, how does it present?
- Fever
- Rash
- Kidney failure
- Leukocytosis
- Eosinophilia
- Abnormal LFTs
Risk factors for pseudogout
- Hyperparathyroidism
- Familial hypocalciuric hypercalcaemia
- Haemochromatosis
- Hypothyroidism
- Hypomagnesia
- Hypophosphataemia
- Gout
- Ageing
- Amyloidosis
- Trauma
- Neuropathic joints
Radiological sign of pseudogout
- Milwaukee shoulder
- Chondrocalcinosis
What is Milwaukee shoulder?
Depositions of crystals within synovium - synovial space no longer black, filled with crystals
What is chondrocalcinosis?
Calcification of cartilage between joints - calcium pyrophosphate deposition
Pseudogout vs gout under microscope
- Gout - needle shaped crystals (negative birefingent)
- Pseudogout - more square shaped (rhomboid and positive birefingent)
Other than monosodium urate crystals in joint aspirate/tophi, other critria for gout diagnosis
Six or more of the following apply:
* More than one attack of acute arthritis.
* Maximum inflammation developed within 1 day.
* Monoarthritis attack, redness observed over joints.
* First metatarsophalangeal joint painful or swollen.
* Unilateral first metatarsophalangeal joint attack.
* Unilateral tarsal joint attack.
* Tophus (confirmed or suspected).
* Hyperuricaemia.
* Asymmetrical swelling within a joint on X-ray film.
* Subcortical cyst without erosions on X-ray film.
* Joint culture negative for organism during attack.
Where are tophi commonly located?
Extensors - eg elbow, knee, achilles tendon or sometimes behind ear
When is urate lowering therapy recommended to be commenced?
- If have 2 or more attacks per year
- If renal disease
- Tophi
- Uric acid renal stones
- Prophylaxis if on diuretics or cytotoxics
