Pseudogout

A. Characteristics of Pseudogout [1]

Calcium Pyrophosphate Dihydrate (CPPD) Deposition Disease
Typically occurs in older persons
1. Incidence may be slightly higher in females
2. Should be ruled out in any patient with calcification of cartilage
3. Often associated with calcification of cartilage (chondrocalcinosis)
4. In younger persons, arthritis may be due to apatite crystals or predisposing conditions
Usually presents as an acute inflammatory monoarthritis [2]
1. Acute presentation most commonly in knees > wrists > ankles
2. May also present as a subacute / chronic arthritis in shoulders, MCPs, wrists
3. Generally not as painful as gout
Disease Associations
1. Disorders of calcium metabolism - hyperparathyroidism
2. Phosphate disorders - hypophosphatemia
3. Renal Failure
4. Hypothyroidism
5. Hemochromatosis
6. Hemosiderosis
7. Amyloidosis
8. Ochronosis
9. Wilson's Disease
May leads to premature osteoarthritis, particularly in knees

B. Diagnosis

Examination of Synovial Fluid Crystals
1. CPPD crystals are positively bifringent
2. Shaped like rectangles or irregular polygons; note crystals in gout are needles
3. May be difficult to find crystals (unlike gouty arthritis)
Radiographs
1. May have calcifications in soft tissue areas on radiographs
2. Typically "smokey" appearance of calcium deposition
3. Chondrocalcinosis - calcification of cartilaginous tissue
Laboratory Analysis
1. Attempt to detect underlying conditions, but usually non-contributory
2. Rule out gout / hyperuricemia - serum urate level
3. Check serum calcium and phosphate levels as well as renal function
4. Consider screening for other abnormalities including thyroid and parathyroid hormones

C. Treatment of Pseudogout [1]

Treatment of Acute Disease - similar to gout
1. NSAIDs - less effective than local depot glucocorticoid injections
2. Colchicine - generally 0.6mg po q2-3 hours
3. Prednisone (steroids) - 30-40mg initially, then tapered over 7-10 days
4. In acute monoarthritis, rule out infection, culture flood, consider glucocorticoid injection
Chronic Suppression of Attacks
1. Same medications as used for acute disease, but in lower doses
2. Colchicine 0.6mg po qd to bid (dosed for renal insufficiency)
3. Prednisone 5-10mg po qd (generally avoided long term)
4. Oral magnesium carbonate (30mEq/day) may be effective in resistant patients
Treatment of Underlying Chronic Disease
1. Check serum calcium and phosphate levels and correct if abnormal
2. Urine calcium, phosphate, uric acid should also be checked
3. Calcium may be lowered with furosemide, phosphate with aluminum binders or calcium

D. Basic Calcium Phosphate (Apatite) Disease

Compounds
1. Hydroxyapatite / carbonates
2. Octacalcium phosphate
3. Tricalcium phosphate
Crystals are usually not seen in microscope
May cause calcific periarthritis, bursitis and tendinits
Usually responds to intra-articular steroids
Usually in younger persons; remitting (and relapsing) course common

E. Milwaukee Joint Syndrome

Typical Presentation
1. Older Women
2. Bilateral Shoulders >50% of patients
3. Significant Shoulder Effusions
Joint Fluid
1. Large, frequently blood tinged shoulder effusions
2. Effusions usually with <1000 cells /µL
3. Contain basic Ca phosphate ± CPPD crystals
Radiographic Appearance
1. Glenohumeral narrowing
2. Knee disease with lateral > medial compartment narrowing
Therapy
1. Poor response to intra-articular steoids
2. May require joint replacement for pain control

F. Cholesterol Crystals

Usually platelike crystals with bifrefingence, tetrahedral shape, 10-80µm size
Often found in rheumatoid effusions
Sometimes found with negatively birefringent, narrow rectangular crystals (not urate)
Lipid droplets are also sometimes found
Significance of these crystals is unknown

References