Learning Objectives
Differentiate Calcium Pyrophosphate Deposition (CPPD) from Gout based on crystal morphology, radiographic findings, and underlying systemic associations. Identify the rhomboid shape and weak positive birefringence of CPPD crystals and recognize the clinical significance of chondrocalcinosis.
1. Pathogenesis & Risk Factors
Calcium pyrophosphate deposition disease (formerly Pseudogout) involves the accumulation of calcium pyrophosphate crystals within the joint space. It typically affects patients > 50 years old, with both sexes affected equally.
- Etiology: Usually idiopathic.
- Systemic Associations: Highly associated with Hemochromatosis, Hyperparathyroidism, and joint trauma.
- Presentation: Can manifest as acute inflammation (pseudogout) or chronic joint degeneration (pseudo-osteoarthritis). The knee is the most commonly affected joint.
Crystal Characteristics & Imaging
Diagnosis is confirmed via synovial fluid analysis showing weakly positive birefringence. On X-ray, the characteristic finding is chondrocalcinosis (calcification of articular cartilage).
| Feature | Finding in CPPD (Pseudogout) |
|---|---|
| Crystal Shape | Rhomboid. |
| Birefringence | Weakly positive. |
| Parallel Light | Blue (“Parallel is Positive Pyrophosphate Plue/Blue”). |
| Imaging (X-ray) | Chondrocalcinosis (linear radiodense deposits in cartilage). |
2. Treatment Strategies
| Phase | Medications | Notes |
|---|---|---|
| Acute Treatment | NSAIDs, Colchicine, Glucocorticoids. | Standard anti-inflammatory management. |
| Prophylaxis | Colchicine. | Used to prevent recurrent acute attacks. |
High-Yield Mnemonics:
- The Blue P’s of CPPD: Pseudogout, Positive birefringence, Pyrophosphate, and Plue (Blue when Parallel).
- Shape: “Rhomboid for the Rheum (CPPD).”