Crystal arthritis

Question 1

What is gout?

Answer 1

Form of inflammatory arthritis characterised by recurrent attacks of a red, tender, hot, and swollen joint, caused by deposition of monosodium urate crystals in and near joints.

Question 2

Why does gout occur?

Answer 2

1. Uric acid has limited solubility in blood so hyperuricaemia can occur.
2. Uric acid replaces a H ion with an Na ion, forming monosodium urate.
3. These crystals are sharp and deposit in the joints (and kidneys), causing severe pain and inflammation.

Question 3

How does gout present?

Answer 3

Usually 1st metatarsal of the big toe, which is painful, red, hot and swollen. (monoarticular)
Fever

Question 4

What else could cause similar symptoms to gout and how would you differentiate it from gout?

Answer 4

Septic arthritis - do joint aspirate MC&S to exclude.

Question 5

What investigations would you do for suspected gout?

Answer 5

WCC
Joint fluid aspirate (MC&S, exclude sepsis)
Polarised light microscopy
X ray - soft tissue swelling, later ‘punched out’ erosions.

Question 6

What would you see under polarised light microscopy in a joint aspirate in gout?

Answer 6

Needle-shaped, Negatively birefringent crystals.

Question 7

Give 3 risk factors for gout.

Answer 7

Male
Diet - alcohol, purine-rich foods: meat/seafood
Drugs: diuretics.
CKD
Age 40-60

Question 8

Describe the management of a gout attack.

Answer 8

Gout attack:
NSAIDs eg ibuprofen
Colchicine (inhibits WBC migration)
Corticosteroids

Question 9

Describe the prevention of gout.

Answer 9

Lose weight, avoid purine-rich foods and alcohol excess and low-dose aspirin.
Allopurinol - inhibits xanthine oxidase so less purine production.

Question 10

What is pseudogout?

Answer 10

Form of inflammatory arthritis characterised by recurrent attacks of red, tender, hot, and swollen joints, caused by deposition of calcium pyrophosphate crystals in connective tissue. = CPPD.

Question 11

How does acute pseudogout normally present?

Answer 11

Acute monoarthropathy, usually affecting larger joints such as the knee in the elderly.

Question 12

What causes acute pseudogout?

Answer 12

Usually spontaneous but can be provoked by illness, surgery or trauma.

Question 13

How does chronic pseudogout present?

Answer 13

Inflammatory RA-like (symmetrical) polyarthritis and synovitis.

Question 14

How would you differentiate pseudogout from gout? Give 3 differences.

Answer 14

Polarised light microscopy: positively birefringent rhomboid-shaped crystals for pseudogout.
X ray - soft-tissue calcium deposition with pseudogout
Gout is more likely to affect the 1st metatarsal of the big toe (monoarticular) while pseudo is more likely to be polyarticular and affect large joints eg knee.

Question 15

Describe the management of pseudogout.

Answer 15

Pseudogout attack:

Symptomatic: Cool packs, rest, aspiration, intra-articular steroids

Question 16

Describe the prevention of pseudogout attacks.

Answer 16

NSAIDs + PPI +/- colchicine (inhibits WBC migration).

Question 17

Give 3 risk factors for pseudogout.

Answer 17

Elderly
Hyperparathyroidism (causes hypophosphataemia)
Haemochromatosis
Dehydration
Surgery/trauma