Crystal Arthropathy Flashcards
What is crystal arthropathy?
Characterised by deposition of mineralised material within joints and peri-articular tissue
Desribe purine metabolism
Endogenous production of uric acid from degradation of purines contributes to 2/3rds of the body urate pool, the remainder being dietary in origin
Of the uric acid produced daily, majority is excreted via the kidney and the remainder is eliminated into the biliary tract and subsequently converted by colonic bacterial uricase to allanotin
What can cause the overproduction of purines?
Malignancy, due to faster turnover of cells and more DNA broken down
Severe exfoliative psoriasis, causing increased cell breakdown
Drugs
Inborn errors of metabolism
HGPRT deficiency/Lesch Nyan Syndrome
What drugs can cause oveproduction of purines?
Ethanol, as high in purine
Cytotoxic drugs as more cell breakdown
What is Lesch Nyan Syndrome?
Enzymatic defect in which purine bases are degraded and excreted as uric acid causing accelerated synthesis of purines to compensate, resulting in overproduction of uric acid
What mode of inheritence is Lesch Nyan Syndrome?
X linked recessive
How does Lesch Nyan syndrome present?
Intellectual disability, gout, renal disease
What can cause underexcretion of uric acid?
Renal Impairment
- Majority of Gout is due to hyperuricaemia resulting from reduced efficiency of renal urate clearance
Hypertension
Hypothyroidism
Exercise, starvation, dehydration
Lead poisoning
What drugs can cause underexcretion of uric acid?
Alcohol
Low dose aspirin
Diuretics
- Perhaps as you are flushing water out, the concentration of uric acid is increased?
Cyclosporine
What is gout?
Inflammatory disease characterised by deposits of monosodium urate crystals within joints
What site does gout usually affect?
Most commonly affects proximal meta-tarsal joint of 1st digit
But can also affect knees, wrist, elbows
What sex does gout most commonly affect?
M>F, perhaps as oestrogen increases uric acid excretion
Give risk factors for gout
DM, as decreased ability to excrete uric acid
Obesity
High BP and cholesterol/Ischaemic heart disease
Alcohol consumption
Diuretic
Dehydration
Ageing, due to decreased renal function
Shellfish
How does gout present?
Symptoms occur at a single joint and onset is usually overnight. An untreated attack can last 2-3 weeks
Severe heat
Pain
Swelling
Tophi
Podagra
Joint deformity in chronic
What are tophi?
Hard nodules over bony prominence in chronic gout due to massive accumulation of uric acid
What is podagara?
Gout of big toe
What investigations are used in gout diagnosis?
Aspirate joint
- Culture to rule out infection
- Polarised Light microscopy to visualize crystals
Uric acid levels not very useful as many flares present with normal levels originally
>CRP, ESR
Imaging
- Peri-articular erosions in chronic gout
What do gout crystals look like under microscopy?
Needle shaped crystals
Negatively birefringent
How is an acute flare of gout managed?
NSAIDS, to decrease pain and swelling
Colchicine, used if NSAIDs are contraindicated ie peptic ulcer
Occasionally steroids if both are contraindicated
What lifestyle management is used in gout?
Reduce alcohol
Weight loss
What pharmacological methods are used in chronic gout management?
Xanthine oxidase inhibitor
- Xanthine oxidase is an enzyme involved in breaking down of purine
Febuxostat
- Nonpurine selective xanthine oxidase inhibiton
- Used as second line when allopurinol is not tolerated
Give an example of a Xanthine Oxidase Inhibitor
Allopurinol
Why do you have to be careful with Xanthine Oxidase Inhibitors?
In acute phase can precipitate an episode of gout, however if already prescribed can continue in current dose
What should be coprescribed with allopurinol?
NSAID or colchicine cover if experiencing an acute flare of gout
What medication should allopurinol be avoided with?
Azathioprine, as risk of bone marrow suppression
How is the 1st attack of gout managed?
Does not need treatment unless single attack of polyarticular gout, torphaceous gout, urate calculi or renal insufficiency
How is 2nd attack of gout managed?
Treat if 2nd attack within 1 year
Wait until acute attack has settled before attempting to reduce urate level, use prophylactic NSAIDS or low dose colchicine/steroids until urate level is normal
When is colchicine used instead of NSAIDS for gout management?
Used when NSAIDS are contraindicated due to GI bleeding history or comorbidities
Give side effects of colchicine
Diarrhoea
N&V
Give complications of gout
Arthritis
- Repeated gouty attacks can lead to chronic gout/permanent monosodium urate crystals in joints
Kidney stones made of uric acid
When is prophylactic treatment of gout used?
Certain malignancies
What is pseudogout?
Inflammatory disease characterised by deposits of calcium pyrophosphate dihydrate within larger joints
What causes pseudogout?
Elderly females
Idiopathic
Associated conditions
- Hyperparathyroidism
- Acromegaly
- Haemochromatosis
- Wilson’s disease
Flare Triggers
- Trauma
- Intercurrent illness
How does pseudogout present?
Pain mainly in the knee
Can be asymptomatic
Swelling
Warmth
Tenderness
What investigations are used in pseudogout diagnosis?
Aspirate Joint
- Visualise crystals with polarised light microscopy
X-Ray
- Chondrocalcinosis/Ca deposits
What do pseudogout crystals look like under microscopy?
Rhomboid crystals
Positive birefringent
How is pseudogout managed?
NSAIDS for acute treatment
Intraarticular corticosteroid injections, use if NSAIDS does not control pain
No prophylactic therapies
