Crystal Arthropathy
Crystal arthropathy is a class of joint disorder (called arthropathy) that is characterized by accumulation of tiny crystals in one or more joints. Polarizing microscopy and application of other crystallographic techniques have improved identification of different microcrystals including monosodium urate, calcium pyrophosphate dihydrate, calcium hydroxyapatite, and calcium oxalate.
Types include:
| Name | Substance | Birefringence |
|---|---|---|
| Gout | accumulation of uric acid | negative |
| Chondrocalcinosis aka Pseudogout | accumulation of calcium pyrophosphate | positive |
Risk factors
- Obesity
- Kidney failure
- Hyperphosphatemia
- Hyperparathyroidism
- Hypercalcemia
- Tissue damage (dystrophic calcification)
Causes
- Deposition of crystals in joints
- Calcium pyrophosphate dihydrate crystal formation:
- Increased production of inorganic pyrophosphate
- Decreased levels of pyrophosphatase in cartilage
- Decreased levels of cartilage glycosaminoglycans
- Hyperparathyroidism
- Hemochromatosis
- Hypophosphatasia
- Hypomagnesemia
- Hydroxyapatite deposition:
- Tissue damage
- Hyperparathyroidism
- Hypercalcemia
- Hyperphosphatemia
- Calcium oxalate deposition:
- Enhanced production of oxalic acid due to enzyme defect
- Poor excretion of oxalic acid in kidney failure
- Excessive ascorbic acid intake in kidney failure
Differential diagnosis
- Septic arthritis
- Type IIa hyperlipoproteinemia
- Amyloidosis
- Multicentric reticulohistiocytosis
- Hyperparathyroidism
- Spondyloarthropathy
- Rheumatoid arthritis
- Fibromyalgia