Crystal Arthropathies Flashcards
Define gout
Inflammation in the joint triggered by uric acid crystals
How is uric acid synthesised?
Dietary purines are converted into hypoxanthine then xanthine then plasma urate finally it is converted into uric acid
What enzyme converts hypoxanthine back to purines?
HGPRT
How does hyperuricaemia arise? What is hyperuricaemia?
Uric Acid >7mg/dL >0.42 mmol/l
- excess consumption
- over production
- under excretion
What causes increased production of uric acid?
- enzyme defects
- myelo/lymphoproliferative disorders
- psoriasis
- haemolytic disorders
- high dietary purine
What causes reduced excretion of uric acid?
- chronic renal impairment
- volume depletion
- hypothyroidism
- diuretics
- cytotoxins
Where does gout tend to occur?
Monoarthropathy of 1st MTP (podagra)
Ankle
Knee
How long does acute gout take to settle with treatment?
3 days
How does gout present?
Abrupt onset, pain, tenderness, swelling, redness
Describe chronic gout
Chronic inflammation often associated with CKD, heart failure or poor compliance with treatments
What can be seen in the joints with chronic gout?
Tophi - crystalline deposits of sodium bitrate
State the investigations used for patients with gout
- serum uric acid
- inflammatory markers
- renal function
- x-ray
- polarising microscopy
What will be seen on polarising microscopy?
negative bifringence, needle shaped crystals
How is acute gout treated?
NSAIDs
Colchine
Steroids
How is chronic gout treated?
Allopurinol, Febuxostat
Started 2-4 weeks after acute attack, NSAIDs may also be required
What is the target serum uric acid level on chronic gout treatment?
<360 micromol/l
What happens in calcium pyrophosphate deposition disease?
Crystals are deposited in the cartilage and articular tissues (hyaline or fibrocartilage)
Where does calcium pyrophosphate deposition usually occur?
Knees, wrists, ankles
How do the crystals in CPDD differ from gout crystals?
Rhomboid shaped crystal are thicker and bigger than urate - positive birefringence
What are the risk factors for CPDD?
- age
- hyperparathyroidism (high calcium)
- previous cartilage problems
- low magnesium
- hypothyroidism
How is CPDD treated?
NSAIDs, colchine, steroids, rehydration
What is another name for hydroxyapatite crystal disease?
Milwankee Shoulder
Describe milwankee shoulder
Usually occurs in 50-60 year old females, deposition in/around the joint leads to release of collangenases serine proteinases and IL1 - rapid deterioration
What is the treatment for milwankee shoulder?
NSAIDs, steroid injections, physic and arthroplasty
