Calcium Pyrophosphate Deposition (CPPD) (Pseudogout, Chondrocalcinosis, Pseudorheumatoid Arthritis)

CPPD in fibrocartilage and hyaline cartilage (chondrocalcinosis) can cause an acute crystal-induced arthritis ("pseudogout"), a degenerative arthropathy, and a chronic inflammatory polyarthritis ("pseudorheumatoid arthritis")

Hyperparathyroidism, familial hypocalcuric hypercalcemia, hemochromatosis, and hypomagnesemia confer risk of CPPD, but most cases 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

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

CPPD may be detected as incidental chondrocalcinosis on radiographs

Identification of weakly positively birefringent 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

NSAIDs are used for acute episodes

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

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