0810 - Crystal Arthropathies

Question 1

Outline the Pathophysiology of Gout

Answer 1

Serum Uric Acid greater than 0.40mmol/L leads to precipitation of monosodium urate crystals in tissues, with attacks occurring when crystals are released into or form in the joint space. Most commonly in big toe MTJ due to cold.
Crystals are phagocytosed by neutrophils, triggering an inflammatory reaction mediated by inflammasome, and producing IL-1.

Question 2

What is inflammasome?

Answer 2

Multiprotein complex that leads to production of IL1-beta, and activation of caspases. Assembly is mediated by NOD-like receptor.

Question 3

What are the initial investigations in suspected crystal arthritis?

Answer 3

Asymptomatic - Fasting lipids and BSL, 24 urine for uric acid.
Monoarticular Gout - FBC, CRP, blood cultures. Serum uric acid, EUC, LFTs, fasting lipids and BSL. Synovial tap for crystals and gram stains (septic arthritis).
Polyarticular Gout - As for monoarticular, plus rheumatoid factor.
Lipids/BSL - associations with metabolic syndrome.

Question 4

What is the gold standard for a diagnosis of gout and pseudogout?

Answer 4

Gout - Presence of Monosodium urate crystals in synovial fluid.
Pseudogout - CPPD crystals.

Question 5

How does hyperuricaemia relate to gout and other conditions?

Answer 5

2/3 hyperuricaemic are asymptomatic, 1/3 progress to gout.
Related to other diseases such as hypertension , insulin resistance, CV disease.
Don’t treat, but require lifestyle modification.

Question 6

DDX for a swollen, inflamed joint?

Answer 6

Septic until proven otherwise
Gout, pseudogout, OA, septic arthritis.
Synovial tap is key.