Crystal arthritis

Question 1

the 2 main types of crystal that account for majority of crystal arthritis

Answer 1

sodium urate

calcium pyrophosphate

Question 2

what happens in all crystal arthritis

Answer 2

neutrophils ingest the crystals and initiate a pro inflammatory reaction

Question 3

Gout and hyperuricaemia

Answer 3

Gout is an inflammatory arthritis caused by hyperuricaemia and intra-articular sodium urate crystals

Gout is the result of excess uric acid in the body, a condition called hyperuricemia. Uric acid is a substance that normally forms when the body breaks down purines, which are found in human cells and in many foods.

Question 4

Gout and hyperuricaemia epidemiology

Answer 4

common
10x more common in M
FHx of gout

Question 5

what does hyperuricaemia result from

Answer 5

overproduction of uric acid or renal under excretion

Question 6

where is urate derived from

Answer 6

the breakdown of purines (adenine & guanine in DNA and RNA), mainly synthesised by the body

Question 7

idiopathic gout

Answer 7

most common form of gout

most have impaired renal function

Question 8

In gout, hyperuricaemia and deposition of sodium urate result in 4 clinical syndromes, what are they?

Answer 8

1. acute sodium urate synovitis - acute gout
2. chronic polyarticular gout
3. chronic tophaceous gout (A form of chronic gout whereby nodular masses of uric acid crystals (tophi) are deposited in different soft tissue areas of the body)
4. urate renal stone formation

Question 9

typical presentation gout

Answer 9

middle aged man

sudden severe pain, swelling, redness of metatarsophalangeal joint of the big toe

Question 10

clinical features gout

Answer 10

metatarsophalangeal joint of the big toe
inflam may extend beyond joint giving impression of cellulitis
the urate crystals trigger intracellular inflammation

Question 11

triggers gout

Answer 11

cold, trauma, sepsis, dehydration, dietary (red meat, seafood, fructose intake) or alcoholic excess, starting a diuretic

Question 12

investigations gout

Answer 12

• joint fluid microscopy: long, needle shaped crystals, negatively birefringent under polarised light
• serum uric acid raised

Question 13

immediate management gout

Answer 13

first line: NSAIDs eg diclofenac or coxibs
second line: colchicine (narrow therapeutic window & v toxic in OD)
corticosterids, ice, vit C

Question 14

how further gout attacks prevented?

Answer 14

by reducing uric acid levels
obese pts: lose weight
reduce alcohol
thiazides and salicylates should be withdrawn (diuretics)
diet: low calorie and cholesterol, avoid purine rich foods (offal, some fish, spinach)

Question 15

chronic gout management

Answer 15

allopurinol - inhibits xanthine oxidase (enzyme in the purine breakdown pathway) = reduces urate levels rapidly

Question 16

pseudogout what is it?

Answer 16

deposition of calcium pyrophosphate dihydrate in articular cartilage and periarticular tissue

Question 17

radiological appearance pseudogout

Answer 17

chondrocalcinosis (linear calcification parallel to the articular surfaces)

Question 18

clinical signs pseudogout

Answer 18

shedding of crystals into a joint produces acute synovitis that resembles acute gout
more common in elderly women
effects the knee or wrist

Question 19

pseudogout associated w what other pathologies in young people?

Answer 19

haemochromatosis, hyperparathyroidism, Wilson’s disease or alkaptonuria

Question 20

investigations pseudogout

Answer 20

joint fluid microscopy - small brick shaped pyrophosphate crystals which are positively birefringent under polarised light (compare with uric acid)
blood count may show raised WCC

Question 21

management

Answer 21

joint aspiration
NSAIDs or colchine
injection of local corticosteroids once septic arthritis excluded