Calcium Pyrophosphate Deposition (CPPD)

Key Features

• CPPD in fibrocartilage and hyaline cartilage (chondrocalcinosis) can cause

  • An acute crystal-induced arthritis ("pseudogout")

  • A degenerative arthropathy

  • A chronic inflammatory polyarthritis ("pseudorheumatoid arthritis")

  • Asymptomatic chondrocalcinosis detected incidentally on radiographs

• Conditions that may confer risk of CPPD include

  • Hyperparathyroidism

  • Familial hypocalciuric hypercalcemia

  • Hemochromatosis

  • Hypomagnesemia

• However, most cases of CPPD have no associated condition

• Usually seen in individuals age 60 yr and older

• Pseudogout, like gout, frequently develops 1–2 days after major surgery

• Familial CPPD is uncommon, but identification of the affected gene as a regulator of inorganic pyrophosphate transport underscores the importance of pyrophosphate homeostasis in the development of CPPD

Clinical Findings

• CPPD can be asymptomatic

• Pseudogout

  • Characterized by acute, recurrent and rarely chronic arthritis involving large joints (most commonly the knees and the wrists)

  • Almost always accompanied by radiographic chondrocalcinosis of the affected joints

  • The crowned dens syndrome

    • Caused by pseudogout of the atlantoaxial junction associated with "crown-like" calcifications around the dens

    • Manifests with severe neck pain, rigidity, and high fever that can mimic meningitis or polymyalgia rheumatica

  • The degenerative arthropathy associated with CPPD can involve joints not usually affected by osteoarthritis (eg, glenohumeral joint, wrist, patellofemoral compartment of the knee)

  • The "pseudorheumatoid arthritis" of CPPD affects the metacarpophalangeal joints and wrists

Diagnosis

• CPPD may be detected as incidental chondrocalcinosis on radiographs

• Identification of calcium pyrophosphate crystals in joint aspirates is diagnostic

• Radiographs demonstrate chondrocalcinosis and degenerative changes (such as asymmetric joint space narrowing and osteophyte formation) in both degenerative arthropathy and "pseudorheumatoid arthritis"

• With light microscopy, the rhomboid-shaped crystals differ from the needle-shaped gout crystals

• A red compensator is used for positive identification, since pseudogout crystals are blue when parallel and yellow when perpendicular to the axis of the compensator

• Urate crystals give the opposite pattern

Treatment

• NSAIDs are used for acute episodes

• Colchicine, 0.6 mg orally once or twice daily, is more effective for prophylaxis than for acute episodes

• In patients with contraindications to other therapies, the use of anakinra, an IL-1 inhibitor, is an option

• Aspiration of the inflamed joint and intra-articular injection of triamcinolone, 10–40 mg, depending on size of the joint, is valuable in resistant cases