Crystal Arthropathies and Polymyalgia Rheumatica Flashcards
What are crystal deposition diseases?
Characterised by deposition of mineralised material within joints and peri-articular tissue
What are commonly seen crystal deposition diseases in practice?
Gout - monosodium urate
Pseudogout - calcium pyrophosphate dihydrate (DPPD)
Calcific peri-arthritis/ tendonitis - basic calcium phosphate hydroxy-apatite (BCP)
Describe the metabolism of purines
Purines are from diet and DNA + RNA
Then make hypoxanthine then xanthine - purine recycled by HGPRT
Then plasma urate which is excreted as urine uric acid
What causes an overproduction of uric acid causing hyperuricaemia?
Malignancy - lymphoproliferative and tumour lysis syndrome
Severe exfoliative psoriasis
Drugs - ethanol and cytotoxic drugs
Inborn errors of metabolism
HGPRT deficiency
What causes an under excretion of uric acid leading to hyperuraemia?
Renal impairment
Hypertension
Hypothyroidism
Drugs - alcohol, low dose aspirin, diuretics and cyclosporine
Exercise, starvation and dehydration
Lead poisoning
Describe Lesch Nyan syndrome
HGPRT deficiency
Is X-linked recessive
Intellectual disability
Aggressive and impulsive behaviour
Self mutilation, gout and renal disease
What is the prevalence of gout in the UK?
Highest in 75+
Higher in males
Increses with age
What is the investigation for gout?
Aspirate and blood test for uric acid but low in serum as all in joint so after treatment of flare then check bloods.
Also renal function tests in blood
US - in chronic there is double layer of crystals seen
What is tophus?
Massive accumulation of uric acid
Can gout be polyarticular?
Yes but commonly mono-articular
How does gout look under microscope?
Needle shaped crystals of gout and negatively bifringed
What is the management of an acute flare of gout?
NSAIDs
Colchicine
Steroids - IA, IM and oral
What is the long term management for gout?
1st attack not treated unless - single attack of polyarticular gout, tophaceous gout, urate calculi and renal insufficiency
Treat 2nd attack within 1 year
Do not treat asymptomatic hyperuricaemia
Address CV and lifestyle factors
What is 1st and 2nd line for lowering uric acid?
1st line - Xanthine oxidase inhibitor ex. Allopurinol
2nd - Febuxostat
What is 3rd line for lowering uric acid?
Uricosuric agents (excrete uric acid) - probenecid and benzbromarone
Canakinumab
What is the rules for lowering uric acid levels?
1 - wait until the acute attack has settled before attempting to reduce
2 - use prophylactic NSAIDs or lose doe colchicine/ steroids until urate levels normal
3 - adjust allopurinol dose according to renal function
What is pseudogout?
The knee is pseudogout and toe is gout
Elderly females
Erratic flares
What is the aetiology and triggers for psuedogout?
Idiopathic, familial and metabolic
Triggers - trauma and intercurrent illness
What can be seen on x-ray of pseudogout?
Chondrocalcinosis -Deposits of calcium in cartilage of joint
Loss of joint space
Sub-chondrosclorosis
Evidence of OA in wrist
How does pseudogout look under microscope?
Pyrophosphate crystals
Very small and not as many
Intracellular rhomboid crystals - positive bifringes
What is the management of pseudogout?
NSAIDs
Intra-articular steroids
There are no prophylactic therapies
What other conditions is polymyalgia rheumatica associated with?
Giant cell arteritis - 20% have this and 50% of GCA have PMR
High ESR anaemia
What is the presentation of polymyalgia rheumatica?
Sudden onset of shoulder and possible pelvic griddle stiffness
ESR usually more than 45 (often 100)
Anaemia, malaise, weight loss, fever and depression
Arthralgia/ synovitis occasionally
What are the factors for polymyalgia rheumatica?
More females to males (2:1)
Rare in under 50 years and usually over 70 year olds
