Pathophysiology of Gout Exam 2

Question 1

In general, how does hyperuricemia occur?

Answer 1

When urate concentration is elevated, blood and extracellular fluid become supersaturated with urate, & deposition of sodium urate crystals in tissues may occur

Question 2

Primary hyperuricemia

Answer 2

• results from naturally-occurring overproduction or underexcretion (or both) of uric acid
• Can be caused as a result of Hypoxanthine-guanine phosphoribosyl transferase (HGPRT) deficiency or Phosphoribosyl pyrophosphate synthetase overactivity

Question 3

Secondary hyperuricemia

Answer 3

• Medications can induce hyperuricemia due to interference with excretion
• Ethanol: Can lead to lactic acidosis which can block uric acid excretion
• Ketosis: Can occur from diabetes, or with starvation
• Renal underexcretion can be caused by: Lead poisoning (“Saturnine” gout), Renal insufficiency
• Dietary purines can affect uric acid concentration
• Purines of meat and fish origin may increase uric acid more than those of vegetable origin.
• Ethanol can increase uric acid production in addition to its effect on excretion.
• Conditions resulting in high cell turnover will increase purines

Question 4

How is uric acid formed?

Answer 4

Uric acid is a product of the metabolism of purines (guanine, adenine); it is formed from xanthine by action of the enzyme xanthine oxidase

Question 5

What is helpful in the diagnosis of gout?

Answer 5

• synovial fluid

- 2015 ACR/EULAR gout classification criteria (Neogi)

Question 6

characteristics of gout synovial fluid

Answer 6

• White blood cell count Inflammatory fluid expected (usually 10,000-60,000 WBC)
• Polarized light microscopy; MSU crystals show negative birefringence (yellow and parallel)

Question 7

2015 ACR/EULAR gout classification criteria (Neogi)

Answer 7

• Entry criterion: >= 1episode swelling, pain, or tenderness in peripheral joint or bursa
• Sufficient criterion: MSU crystals in symptomatic joint, bursa, or tophus
• Criteria (if sufficient criterion not met; points given for elements below. Score of >=8/23 classified as gout)

Question 8

What crystals are involved in pseudogout?

Answer 8

Calcium pyrophosphate dihydrate deposition (CPPD)

Question 9

Diagnosis of pseudogout

Answer 9

Need CPPD crystals for definitive diagnosis - rhomboid crystals (instead of needle shape) with weak positive birefringence