Gout and pseudogout Flashcards
epidemiology, pathophysiology, presentation, investigation, management and prognosis
What is crystal arthropathy?
An inflammatory joint disorder resulting from deposition of crystals in the joint and surrounding soft tissues
What are the 2 types of crystal arthropathies?
Gout
Pseudogout/calcium pyrophosphate dihydrate (CPPD)
What is the difference between the crystals found in gout and pseudogout?
Gout is characterised by monosodium urate crystals
Pseudogout is characterised by calcium pyrophosphate crystals
What is the most common inflammatory arthritis in men over 40?
Gout
When in a women’s lifespan is gout most common?
Post-menopause
Why is gout most common in post-menopause stage then any other time in a woman’s life?
Oestrogen has an uricosuric effect (increases uric acid excretion)
Post-menopausal stage has decreased oestrogen levels, so excess uric acid isn’t excreted and builds up and crystallises
What is the prevalence of gout in individuals with comorbidities then prevalence of gout in individuals with no other conditions?
Gout is significantly more prevalent in individuals with comorbidities
Give 5 examples of common comorbidities of individuals with gout?
Hypertension, diabetes, CVD, Chronic Kidney Disease (CKD), obesity
Who amongst the ageing population is most likely to have severe gout attacks?
Individuals with medications to treat comorbidities
If an elderly individual takes diuretics to prevent heart failure, how can this increase the likelihood of gout attacks occuring?
Diuretics decrease uric acid excretion, so crystals can form
Is pseudogout more common in young or elderly populations?
Elderly populations, over 50 years old
What percentage of individuals aged 65-75 have pseudogout?
10-15%
What percentage of individuals aged over 85 have pseudogout?
30-60%
What condition does gout pathophysiology arise from, and define this condition?
Hyperuricaemia: abnormally high serum uric acid levels
What are the 2 types of uric acid production, and how can they cause hyperuicaemia?
Exogenous and endogenous uric acid overproduction can lead to build up of serum uric acid
What is exogenous uric acid production, and what type of purine precursor is used in the reaction?
Production of uric acid from exogenous purines, which are absorbed by body from consumed food
What is endogenous uric acid production, and what type of purine precursor is used in the reaction?
Production of uric acid from endogenous purines, which are made directly by body itself
How can high alcohol consumption/alcohol abuse cause hyperuricaemia?
Alcohol increases exogenous production of uric acid
What 2 groups of disorders increase endogenous production of uric acid, leading to hyperuricaemia?
Myeloproliferative
Lymphoproliferative
How can abnormal renal handling of urate result in hyperuricaemia?
Causes underexcretion of uric acid
What are 2 diseases that cause abnormal renal handling of urate?
Renal disease
Polycystic kidney disease
What percentage of individuals with hyperuricaemia/primary gout are underexcretors of uric acid?
90%
What are the 3 causes of hyperuricaemia that can result in gout?
Exogenous/endogenous overproduction of uric acid
Underexcretion of uric acid due to abnormal renal handling
Combination of overproduction and underexcretion of uric acid
Name 8 substances that cause hyperuricaemia (CANT LEAP)?
Cyclosporine
Alcohol
Nicotinic acid
Thiazides
Lasix (frusemide)
Ethambutol
Aspirin (low dose)
Pyrazinamide
How is monosodium urate formed from uric acid in gout?
Uric acid ions combine with sodium ions to from monosodium urate (a common salt)
How are calcium pyrophosphate crystals formed in pseudogout?
Excess pyrophosphate complexes combine with calcium
What is the pathophysiology of pseudogout?
Calcium pyrophosphate crystals form in joint cartilage, then are shed into synovial fluid in synovium/joint lining
In gout and pseudogout, what triggers inflammation of the joint/synovium?
Build up of crystals
What is the volume of synovial fluid in a normal knee joint compared to in a gouty/pseudogouty knee joint?
less than 3.5 ml in normal knee joint
More than 3.5 ml in gouty/pseudogouty knee joint
What is the viscosity of synovial fluid in a normal knee joint compared to in a gouty/pseudogouty knee joint?
Very high viscosity in normal knee joint
Very low viscosity in gouty/pseudogouty knee joint
What is the colour of synovial fluid in a normal knee joint compared to in a gouty/pseudogouty knee joint?
Clear synovial fluid in normal knee joint
Opaque, straw-coloured synovial fluid in gouty/pseudogouty knee joint
What is the WBC/mm3 of synovial fluid in a normal knee joint compared to in a gouty/pseudogouty knee joint?
200 mm3 in normal knee joint
Over 100,000mm3 in gouty/pseudogouty knee joint
What is the percentage of neutrophils composing synovial fluid in a normal knee joint compared to in a gouty/pseudogouty knee joint?
Less than 25% in normal knee joint
Over 50% in gouty/pseudogouty knee joint
What procedure is used to obtain a synovial fluid sample from a joint, and what are the steps?
Joint aspiration
Insert needle into joint and remove synovial fluid, send culture to lab