Crystal arthropathies Flashcards
pathophysiology of gout?
A type of crystal arthropathy associated with chronically high blood uric acid levels
monosodium urate crystals are deposited in the joint causing it to become hot, swollen and painful
Gouty tophi are subcutaneous deposits of uric acid typically affecting the small joints and connective tissues of the hands, elbows and ears. The DIP joints are most affected in the hands.
Clinical presentation of gout?
It typically presents with a single acute hot, swollen and painful joint. The obvious and extremely important differential diagnosis is septic arthritis.
Risk factors of gout?
Male
Obesity
High purine diet (e.g. meat and seafood)
Alcohol
Diuretics
Existing cardiovascular or kidney disease
Family history
Typical joints affected in gout?
Base of the big toe (metatarsophalangeal joint)
Wrists
Base of thumb (carpometacarpal joints)
Gout can also affects large joints like the knee and ankle.
Diagnosis of gout
Gout is diagnosed clinically or by aspiration of fluid from the joint. Excluding septic arthritis is essential as this is a potential joint and life-threatening diagnosis.
Aspirated fluid will show:
No bacterial growth
Needle shaped crystals
Negatively birefringent of polarised light
Monosodium urate crystals
Joint X-ray with gout?
Typically the space between the joint is maintained
Lytic lesions in the bone
Punched out erosions
Erosions can have sclerotic borders with overhanging edges
Management of gout during an acute flare?
NSAIDs (e.g. ibuprofen) are first-line
Colchicine second-line
Steroids can be considered third-line
Colchicine is used in patients that are inappropriate for NSAIDs, such as those with renal impairment or significant heart disease. A notable side effect is gastrointestinal upset. Diarrhoea is a very common side effect. This is dose-dependent meaning lower doses cause less upset than higher doses.
Prophylaxis of gout?
Allopurinol is a xanthine oxidase inhibitor used for the prophylaxis of gout. It reduces the uric acid level.
Lifestyle changes can reduce the risk of developing gout. This involves losing weight, staying hydrated and minimising the consumption of alcohol and purine-based food (such as meat and seafood).
TOM TIP: do not initiate allopurinal prophylaxis until?
After the acute attack is settled
Once treatment of allopurinal has been started then it can be continued during an acute attack
What is Pseudogout?
Pseudogout is a crystal arthropathy caused by calcium pyrophosphate crystals. Calcium pyrophosphate crystals are deposited in the joint causing joint problems. It is also known as chondrocalcinosis.
Diagnosis of pseudogout?
In any patient presenting with a hot, painful and swollen joint, septic arthritis needs to be excluded as it is a medical emergency that is joint and life threatening. It tends the be milder in presentation compared with gout and septic arthritis.
To establish a definitive diagnosis the joint needs to be aspirated for synovial fluid.
Aspirated fluid will show:
No bacterial growth
Calcium pyrophosphate crystals
Rhomboid shaped crystals
Positive birefringent of polarised light
Xray change in psuedogout?
Chondrocalcinosis is the classic xray change in pseudogout. It appears as a thin white line in the middle of the joint space caused by the calcium deposition. This is pathognomonic (diagnostic) of pseudogout.
Other joint xray changes are similar to osteoarthritis. Remember the mnemonic LOSS:
L – Loss of joint space
O – Osteophytes
S – Subarticular sclerosis
S – Subchondral cysts
Management of pseudogout?
Chronic asymptomatic changes found on an xray do not require any action.
Symptoms usually resolve spontaneously over several weeks. Symptomatic management involves:
NSAIDs
Colchicine
Joint aspiration
Steroid injections
Oral steroids
Joint washout (arthrocentesis) is an option in severe cases.
