Chondrocalcinosis

Calcium pyrophosphate deposition disease (CPPD) is a rheumatologic disorder with varied clinical manifestations due to precipitation of calcium pyrophosphate dihydrate crystals in the connective tissues. It is more commonly known by alternative names that specify certain clinical or radiographic findings, although neither is synonymous with CPPD. Pseudogout refers to the clinically evident acute synovitis with red, tender, and swollen joints that may resemble gouty arthritis (a similar condition with joint deposition of monosodium urate crystals). Chondrocalcinosis, on the other hand, refers to the radiographic evidence of calcification in hyaline and/or fibrocartilage. Pyrophosphate arthropathy is a term that may refer to either of the above, but is uncommonly used.

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Clinical aspects

CPPD crystal deposition disease is a polyarticular arthritis (i.e. it leads to an inflammation of several joints in the body), although it can initially present as monoarticular (i.e. confined to just one joint).

CPPD crystals tend to form within articular tissues. Diagnosis is by microscopy of fluid from a joint aspiration. Rhomboidal crystals should be seen under the microscope which exhibit weakly positive birefringence under polarized light. X-rays of the joint may show signs of chondrocalcinosis. Asymptomatic deposits can form in cartilage, joint capsules, intervertebral discs, tendons, and ligaments. Crystal deposition within cartilage (both hyaline and fibrocartilage) is known as chondrocalcinosis. Chondrocalcinosis initially is only visible microscopically, but if there is enough calcification, it can be seen radiographically as well. Common locations of chondrocalcinosis include the knees, wrists, elbows, and hips.

Crystal-induced synovitis is the result of shedding of crystals in the joint space after rupture of a CPPD deposit. Clinically this presents as an acute inflammatory synovitis very similar to that of an attack of gout, and has been referred to as "pseudogout."

• Other conditions associated with chondrocalcinosis:
  • hyperparathyroidism
  • hemochromatosis
  • hypophosphatemia
  • Renal osteodystrophy

Radiologic findings

Three main manifestations of CPPD deposition:

1. chondrocalcinosis
2. crystal induced synovitis (pseudogout syndrome)
3. pyrophosphate arthropathy

Treatment

Treatment of CPPD is mostly aimed at preventing further crystal formation and reducing symptoms from crystal deposition. CPPD crystal deposition cannot be reversed. If CPPD results from underlying metabolic abnormalities (hyperparathyroidism, hemochromatosis, hypophosphatasia, or hypomagnesemia)^[1], these can be treated directly.

For symptomatic joints, treatment is similar to treatment of gout. When a single joint is involved, joint aspiration and intra-articular corticosteroid injection is often used, in addition to NSAIDs and/or colchicine. When multiple joints are involved, joint injection is often impractical, or limited only to the most severely involved joint, and oral systemic treatment is chosen instead.

Because pyrophosphate complexes with magnesium prior to its degradation^[2], and CPPD can result from pathologically low magnesium levels, magnesium supplementation may be of help, particularly in a few patients with underlying hypomagnesemia. It may be possible to end attacks by ingesting large (maximum RDA) doses of magnesium supplement accompanied by vitamin B6 to help absorption. What that does is assist the body in re-dissolving the calcium in the joint fluid^{[citation needed]}, and with maintenance doses, often in the form of snacking on magnesium-rich foods such as almonds, further attacks can be prevented altogether - without medication^{[citation needed]}.

References

• Calcium pyrophosphate deposition disease by Marla Sammer, M.D. and Rob Gutierrez, M.D., University of Washington Department of Radiology
• Steinbach LS, Resnick D. Calcium pyrophosphate dihydrate crystal deposition disease: imaging perspectives. Curr Probl Diagn Radiol. 2000 Nov-Dec;29(6):209-29.
• Chew FS, Maldijian C, Leffler SG. Musculoskeletal Imaging: A Teaching File, Lippincott Williams & Williams, 1999.