Monosodium urate (MSU) crystals
Needle-shaped
Intracellular, approximate diameter of neutrophil
Strongly negatively birefringent (yellow)
Gout
Calcium pyrophosphate dihydrate (CPPD) crystals
Rhomboid-shaped
Weakly positively birefringent (blue)
Psuedogout
Chondrocalcinoisis (x-ray)
Osteoarthritis
Calcium basic phosphate (CBP) crystals
Small - only identified by electron microscopy
Not birefringent
Clumps of crystals (shiny coins) under LM
Alizarin red stain to detect calcium-containing crystals
Acute inflammatory arthritis (young people)
Milwaukee shoulder (older people)
Calcium oxalate crystals
bipyramidal and envelope shaped
Stain with alizarin red
Primary oxaluria (autosomal recessive)
Kidney failure on hemodialysis
Cholesterol crystals
Very large
Flat and rectangular shaped
Notched corners
Varying birefringence
Rheumatoid arthritis
Corticosteroid crystals
Iatrogenic
Strongly variably birefringent
Polymorphic clumps, rods, or rhomboids
May cause joint pain for several hours
Talc crystals
Iatrogenic
Originate from latex gloves during arthrocentesis
Strongly birefringent
Maltese cross pattern
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