Crystal Arthropathy

Question 1

What are common crystal deposition diseases characterised by?

Answer 1

Deposition of mineralised material within joints and periarticular tissue.

Question 2

What are some examples of common crystal deposition diseases?

Answer 2

Monosodium urate - Gout
Calcium Pyrophosphate dihydrate - Pseudogout.
Basic calcium phosphate hydroxy-apatite - calcific periarthritis/tendonitis.

Question 3

What are tophi?

Answer 3

Massive accumulations of uric acid.

Question 4

How is urate produced in the body?

Answer 4

Degradation of purines produced either from DNA/RNA or the diet.

Purines - Hypoxanthine - xanthine - plasma urate - urine uric acid.

Question 5

How is uric acid removed from the body?

Answer 5

Majority is excreted via the kidney and the remainder is eliminated into the biliary tract and subsequently converted to colonic bacterial uricase to allantoin.

Question 6

What are some causes of hyperuricaemia?

Answer 6

Overproduction:
Malignancy e.g. lymphoproliferative, tumour lysis syndrome. 
Severe exfoliative psoriasis
Drugs e.g. ethanol, cytotoxic drugs
Inborn errors of metabolism
HGPRT deficiency. 

Under excretion:
Renal impairment
Hypertension
Hypothyroidism
Drugs e.g. alcohol, low dose aspirin, diuretics, cyclosporin
Exercise
Starvation
Dehydration
Lead poisoning

Question 7

What is Lesch Nyan Syndrome?

Answer 7

HGPRT deficiency resulting in overproduction uric acid.
x-linked recessive condition
Characterised by intellectual disability, aggressive and abusive behaviour, self mutilation, gout and renal disease.

Question 8

Why is gout predominantly a disease of men?

Answer 8

Men have higher levels of urate.
Oestrogen has an uricosuric effect making gout rare in young women.
Thought to be a disease of rich foods and alcohol which men are stereotypically more likely to have such as steak and beer.

Question 9

How is an acute flare up of gout managed?

Answer 9

NSAIDs
Colchicine
Steroids

Question 10

How is Hyperuricaemia managed?

Answer 10

1st attack not treated unless single attack of polyarticular gout, tophaceous gout, urate calculi or renal. insufficiency.
Treat 2nd attack within 1 year.
Do not treat asymptomatic hyperuricaemia.

Question 11

What agents can be used to lower uric acid levels?

Answer 11

Xanthine oxidase inhibitor - Allopurinol.
Febuxostat
Uricosuric agents - sulphinpyrazone, probenecid, benzbromarone.
Canakinumab.

Question 12

What are the rules regarding lowering uric acid levels?

Answer 12

Wait until the acute attack has settled before attempting to reduce urate level.
Use prophylactic NSAIDs or low dose colchicine/steroids until urate level normal.
Adjust allopurinol dose according to renal function.

Question 13

What are some characteristics of pseudogout?

Answer 13

Knee is common site.
Elderly females are commonly affected.
Erratic flare ups
Idiopathic, familial or metabolic causes.
Trauma and intercurrent illness can be triggers.

Question 14

What is the management of pseudogout?

Answer 14

NSAIDs
I/A steroids
No prophylactic therapies.

Question 15

What is polymyalgia rheumatica?

Answer 15

Inflammatory condition of the elderly. Close relationship with giant cell arthritis which results in high ESR anaemia.

Question 16

What are the characteristics of polymyalgia rheumatica?

Answer 16

Sudden onset of shoulder and pelvic girdle stiffness. 
Rare
F>M
ESR usually > 45 often 100. 
Anaemia
Malaise
Weight loss
Fever
Depression
Arthralgia and synovitis occur occasionally.

Question 17

How is polymyalgia rheumatica diagnosed?

Answer 17

Compatible history
Age >50
ESR >50
Dramatic response to steroids

Question 18

What is the treatment for polymyalgia rheumatica?

Answer 18

Prednisolone 15mg per day initially.
18-24month course
Bone prophylaxis