Crystal Arthropathies Flashcards
Name the 2 types of crystal arthropathies?
Gout
Pseudogout
What is meant by ‘crystal arthropathies’?
Deposition of crystals in joints causing arthritis
What is Gout?
Deposition of monosodium urate crystal in and near joints
Which joints are particularly affected by Gout?
The metatarsophalangeal joint of the big toe
Hand and foot joints are most often affected
But any joint can be
Which crystal is involved in Gout?
Monosodium urate
What conditions does Gout increase the risk of?
Cardiovascular disease:
- stroke
- MI
Renal disease
Diabetes
How is uric acid processed by the body?
It is carried around the body in the bloodstream
You get rid if it via the kidneys
What is the difference between urate and uric acid?
Urate is the salt of uric acid
What causes a rise in urate in the body?
Genetic conditions that affect the absorption of urate
Increased intake in diet
Increased cell turnover: like in psoriasis
Cell damage or death: surgery/chemo
Kidney problems that mean they can’t get rid of urate properly
Drugs
Why do crystals form?
When concentration of urate gets too high in the blood crystals begin to form
As with any concentrated substance
When treating gout you want to reduce uric acid levels in the blood. To what level are you aiming for?
About 300, low enough that crystals don’t form
Clinical features?
A chronic disease, but now and then attacks occur
Attacks:
A hot, red, inflamed joint
Often starts overnight and wakes them up
It is intense pain, can’t even stand bedsheets touching the joint
Causes of gout?
Diet: an excess of:
- alcohol
- red meat
- seafood
- fructose, sugary food/drinks
Renal problems:
- unable to filter urate out
Hereditary:
- psoriasis, increased cell proliferation
Cherries are protective in gout. What else is?
Dairy
Other sources of vitamin C
Investigation of gout?
Aspirate and collect crystals to analyse
Blood:
- serum urate levels raised
X-rays:
- show soft tissue swelling early on, bone deformity later
Why is gout painful?
The urate crystals trigger intracellular inflammation which causes swelling and damage = intense pain
Are gout attacks self-limiting? Why/why not?
Yes in about 3-5 days
By then the macrophages and monocytes have matured and realised what’s going on
They start to produce anti-inflammatory cytokines
Management of an acute gout attack?
NSAID or COX inhibitor for pain relief
Colchine - an anti-inflammatory agent
Steroids
Ice
Rest + elevate
Cherries and Vit C help to speed up resolution
Management of chronic gout, between attacks?
Stop diuretics if they are on them and it is safe to do so
Switch to an alternative
Anti-cholesterol
Lower uric acid levels with allopurinol
Lifestyle modification:
- diet
- weight loss
- alchohol reduction
How do you analyse crystals aspirated from the joint?
Describe the appearances of gout and pseudogout crystals?
View under polarised light microscopy
Gout: fluoresce negatively
Pseudogout: fluoresce positively
What is pseudogout and why does it have this name?
Deposition of calcium pyrophosphate crystals on joint surface
Because it looks and feels like gout but its not
Which crystals are involved in pseudogout?
Calcium pyrophosphate
Which joints are usually involved in pseudogout?
Metacarpophalangeal
Wrists
Knees
Ankles
Clinical features of pseudogout?
Same as gout
Acute
Hot joint
Appears osteoarthritic
How can you distinguish between gout and pseudogout?
Aspirate the joint
View the crystals under polarised light microscopy
Positive fluorescence = pseudogout
Negative = gout
Risk factors of pseudogout?
Old age
Hyperparathyroidism
Haemochromatosis
Treatment of pseudogout?
Steroids
Colchicine
NSAIDs
