Crystal Arthropathies Flashcards
What are the two conditions which are classed as crystal arthropathies?
Gout and pseudogout
What crystals are associated with gout?
Monosodium urate
What crystals are associated with pseudo gout?
Calcium pyrophosphate
How quickly do crystal arthropathies usually present and how long do they last?
Present acutely and last 2 weeks max
What can repeated attacks of gout cause?
Destructive, erosive arthritis causing deformities
What is a typical presentation of gout?
Intensely painful, red, hot, swollen joint
Gout often mimics which other condition?
Septic arthritis
Is gout inflammatory?
Yes
What can the crystal deposition in gout be triggered by?
Dehydration, trauma or surgery
Monosodium urate crystal deposition in gout is usually due to what?
Increased serum uric acid levels (hyperuricaemia)
How common is gout?
The most common medical condition in adults of the industrialised world
Which sex is gout most common in?
Men
What is the relationship between gout and age?
Prevalence of gout increases with age
What is the most common arthritis in men?
Gout
What are the purines in DNA?
Adenine and guanine
Where do purines in the body come from?
Breakdown of DNA or from the diet
What are the breakdown stages from purine to uric acid?
Purine –> Hypoxanthine –> Xanthine –> Plasma urate –> Uric acid
What enzyme is involved in changing purines to uric acid?
Xanthine oxidase
What is lost during the process of changing purines to uric acid?
O2
Can genetics increase the risk of gout?
Yes
Uric acid is the final product in the breakdown of what?
Purines in DNA metabolism
What are the two main causes of hyperuricaemia?
Under-excretion or over production
What are examples of under excretion of uric acid?
Diuretic use, renal failure, starvation/dehydration, hypo/hyperparathyroidism, drugs, alcohol
What are examples of over production of purines?
Excessive intake of alcohol, seafood, red meat, genetics or increased cell turnover
What are some causes of high cell turnover?
Psoriasis, extreme diets, infections, anaemia, chemotherapy
What defines hyperuricaemia?
Serum uric acid > 7mmol/dL
What is the relationship between hyperuricaemia and gout?
Having hyperuricaemia does not mean you have gout, it just increases the risk of you getting it
What are the three main sites of gout?
- 1st MTP (known as Podagra)
- Ankles
- Knees
What is the diagnosis of gout based on?
Identification of crystals or classic radiographic findings
What happens to uric acid to cause an acute of gout?
Acute changes in the levels of uric acid
When is the best time to measure serum uric acid?
2-4 weeks following an acute attack
Why should you not measure uric acid at the time of an acute attack?
25% of people can have a normal uric acid then
What are three differential diagnoses of gout?
- Septic arthritis
- Trauma
- Seronegative arthritis
What is chronic polyarticular gout?
Chronic joint inflammation after having recurrent acute attacks of gout, often associated with diuretic use
What is the gold standard investigation for gout?
Joint aspirate
What other three investigations can be used for gout?
X-ray, inflammatory markers, WCC
What will inflammatory markers show in gout?
Raised
What will an x-ray show in gout?
Normal in acute attacks, erosions, osteophytes, joint destruction after recurrent attacks
What is a joint aspirate?
A sample of synovial fluid with polarised microscopy
As well as crystals, what else is investigated for during a joint aspirate?
The fluid us analysed with gram stain and culture to exclude infection
What will gout show on joint aspirate?
Needle shaped crystals with negative birefringence (change from yellow to blue when lined across the direction of polarisation)
What is the mainstay of treatment for an acute attack of gout if there are no contraindications?
NSAIDs
If a patient with gout cannot have NSAIDs what should they use?
Colchicine
What are the other two treatment options for the acute treatment of gout?
Steroids or stronger painkillers
What lifestyle modifications can reduce gout?
Restrict risk factors, reduce alcohol, lose weight, fluids
What are tophi?
Painless, white accumulations of uric acid which can occur in the soft tissues and occasionally erupt through the skin
What are indications for prophylaxis of gout?
- > 2 attacks
- Tophi
- Erosions on x-ray
- Renal stones
What are two examples of urate lowering therapies?
Allopurinol and febuxostat
When should urate lowering therapy be started?
2-4 weeks following an acute attack
Why should urate lowering therapy not be given while there is still an acute attack?
Can make it worse and potentiate a future flare
What target serum urate should you be aiming for on urate lowering therapy?
< 0.3mmol/l
What is pseudogout also known as?
Calcium pyrophosphate deposition disease (CPPD)
Who does pseudo gout occur more commonly in? Why?
Elderly- chondrocalcinosis increases with age
What is chondrocalcinosis?
Calcium pyrophosphate deposition in cartilage and soft tissues in the absence of acute inflammation
Where does chonedrocalcinosis affect?
Fibrocartilage in the knees, wrists and ankles
What is the relationship between pseudo gout and OA?
Pseudogout can occur when there is already OA, or chronic CPPD can cause OA
How do you tell the difference between gout and pseudo gout?
Joint aspirate
What will pseudo gout show on joint aspirate?
Rhomboid/envelope shaped crystals with weakly positive birefringence
Is it possible to have both gout and pseudo gout?
Yes
What diseases can pseudo gout co-exist with?
Hyperparathyroidism, hypothyroidism, renal osteodystrophy, haemochromotosis, Wilson’s disease
What is the management for pseudo gout?
NSAIDs, colchicine, steroids, rehydration (only acute management here)
What is Milwaukee shoulder?
Deposition of hydroxyapatite crystals in or around the joint
What does Milwaukee shoulder cause and who is it mostly seen in?
An acute and rapid deterioration in females aged 50-60 years
What is the only way to detect Milwaukee shoulder?
Alizarin stain will show red clumps
