Gout and CPPD - Flusser

Question 1

What is the difference between crystals seen under polarized light in gout versus in pseudogout?

Answer 1

In gout:

• Monosodium urate monohydrate crystals
• Yellow needles seen parallel to the axis of the compensator
• Blue needs seen perpendicular to the compensator
• Crystals are negatively birefringent

In psuedogout:

• calcium pyrophosphate dihydrate crystals
• Blue trapezoids seen parallel to axis, yellow perpendicular
• Positively birefringent

Question 2

What is the clinical presentation of acute gouty arthritis?

Answer 2

Abrupt onset of severe joint inflammation, tingling at night

Sibsides completely in 3-10 days

5% in first MTP joint (podagra)

Urate crystals in synovial fluid

May have hyperuricemia before attacks

Usually monoarticular but may be polyarticular

A week after the episode ther eis diffuse cellulitis with skin changes

Different from RA:
Juxta-articular osteoporosis absent
Punched out, sclerotic and overhanging edges

Different from OA:
Joint space well preserved

Question 3

What are the differences in epidemiology between gout and pseudogout?

Answer 3

Classical location in gout is 1st MTP and in pseudogout is the wrist and knee

Gout patients are younger

Gout patients are more often male, pseudogout female

Sodium urate crystals only in gout

Calcification usually absent in gout

Erosion is “punched out” in gout and often degenerative (like OA) in CPPD

Crystals:
in gout, MSUM vs CPPD
Needle vs trapezoidal
Strong, negative birefringence (yellow parallel) vs weak positive birefringence (blue parallel)

Question 4

How is CPPD distinguished from osteoarthritis?

Answer 4

Pseudogout has:

Distribution along wrists, shoulders and ankles (not common in OA)

Giant osteophytes

Charcot-like distructive changes in some cases