Crystal-induced arthropathies

Question 1

How do organic anions + thiazides promote hyperuricemia?

Answer 1

They act at the URAT1 exchanger in the kidney- they go out into the lumen while urate is reabsorbed. Thus, if there are higher concentrations of organic acids/ thiazides, then they are excreted more while urate is reabsorbed more.

Question 2

Presentation of gout attack

Answer 2

Abrupt, rapid onset of monoarticular pain, swelling, erythema

Question 3

Complication of chronic gout

Answer 3

Renal failure- due to urate crystal deposition in kidney (urate nephropathy)

Question 4

Primary vs. secondary gout

Answer 4

Primary gout- etiology of hyperuricemia is not exactly known (most common form)

Secondary gout- etiology is known

Question 5

Pattern of joint involvement in gout attack

Answer 5

Monoarticular involvement; MTP joint most commonly affected (podagra), other joints include ankle, heel, knee, and wrist

Question 6

Where does crystals deposit in gout vs. CPPD

Answer 6

In CPPD, crystals deposit exclusively in articular cartilage. In gout, crystals deposit in synovial space + soft tissue

Question 7

What is chronic gout characterized by?

Answer 7

Development of tophi- white chalky aggregates of uric acid crystals w/ fibrosis

Question 8

Why alcohol can cuase hyperuriecmiea

Answer 8

Competes for same excretion site as uric acid

Question 9

Factors that promote hyperuricemia

Answer 9

Alcohol, meat/seafood consumption (high purines), organic acidosis, obesity, diuretics, rneal disease

Question 10

First step in diagnosing gout

Answer 10

Always aspirate the joint in order to rule out septic arthritis. Then identify crystals

Question 11

Characteristic of monosodium urate crystals

Answer 11

Strongly negative birefringent- yellow when parallel + blue when perpendicular

Crystals are fine needle shaped

Question 12

Pathophysiology of urate crystal formation

Answer 12

Urate crystals precipitate in joints –> neutrophils + macrophages phagocytize –> IL-1 and other cytokines released –> infalmmatoryt reaction –> tissue/joint injury

Question 13

Characteristic of calcium pyrophosphate crystals

Answer 13

Weakly berefringent udner polarized light (blue when parallel to light)

Rhomboid shape

Question 14

Imaging finding for calcium pyrophosphate deposition

Answer 14

Chondrocalcinosis- cartilage calcification

Question 15

Common causes of secondary gout

Answer 15

• High cell-turnover rates (e.g. myeloproliferative disorders, psoriasis, lymphoma) + tumor lysis w/ chemo
• Genetic disorders (e.g. Leisch Nyhan syndrome)
• Renal failure (decreased excretion of urate)