Calcium pyrophosphate dihydrate deposition disease
Calcium pyrophosphate dihydrate disease (CPPD disease), also referred as pyrophosphate arthropathy and perhaps confusingly as pseudogout, is common, especially in the elderly, and is characterised by the deposition of calcium pyrophosphate in soft tissues and cartilage.
CPPD is one of many causes of soft tissue calcification (chondrocalcinosis). It is not synonymous with chondrocalcinosis and not the only cause of soft tissue calcification.
Where crystal deposition causes acute clinical manifestation, the term pseudogout should be used. Pyrophosphate arthropathy is a term that describes arthropathy secondary to CPPD deposition. However, it is often used indiscriminately to refer to chondrocalcinosis too.
CPPD is commonest in patients over the age of 50. Men and women are equally affected.
The crystals are weakly positively birefringent on polarised microscopy and have a rhomboid or rod shape. Causes of CPPD can be divided into:
- AD pattern; mutation in gene ANKH encoding transmembrane inorganic pyrophosphate transporter
CPPD has many features of osteoarthritis with unusual distribution, for example, they tend to be symmetric in distribution and involve non-weight bearing joints or, in the hands, mainly involve intercarpal and MCP joints.
Features of degenerative joint disease in joints that are not commonly affected by it (i.e. non-weight bearing joints):
- wrist joint (mainly radiocarpal and scapholunate joints)
- patellofemoral joint
- shoulder joint
- elbow joint
Chondrocalcinosis can occur in many locations. Notable sites include:
- knee: medial meniscus and patellofemoral joint
- wrist: triangular fibrocartilage complex and lunotriquetral ligaments
- spine: periodontoid tissue
Large subchondral cysts may be present.
It is controversial whether gout leads to calcification of articular fibrocartilage or hyaline cartilage 6. CPPD disease can be differentiated from gout on ultrasound given that echogenic monosodium urate crystals line the surface of articular cartilage, whereas echogenic CPPD calcifications are located within the cartilage itself 7.
Possible imaging differential considerations include
- usually have the typical weight-bearing distribution
giant cell tumour (GCT)
- subchondral cysts of CPPD can be large and simulate subchondral GCT
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- 2. Whelan BR, O'shea F, Mccarthy G. Pseudoneuropathic CPPD arthropathy: magnesium matters. Rheumatology (Oxford). 2008;47 (4): 551-2. doi:10.1093/rheumatology/ken016 - Pubmed citation
- 3. El-khoury GY, Tozzi JE, Clark CR et-al. Massive calcium pyrophosphate crystal deposition at the craniovertebral junction. AJR Am J Roentgenol. 1985;145 (4): 777-8. AJR Am J Roentgenol (citation) - Pubmed citation
- 4. Kaushik S, Erickson JK, Palmer WE et-al. Effect of chondrocalcinosis on the MR imaging of knee menisci. AJR Am J Roentgenol. 2001;177 (4): 905-9. AJR Am J Roentgenol (full text) - Pubmed citation
- 5. Scutellari PN, Galeotti R, Leprotti S et-al. The crowned dens syndrome. Evaluation with CT imaging. Radiol Med. 2007;112 (2): 195-207. doi:10.1007/s11547-007-0135-7 - Pubmed citation
- 6. Brower AC, USNR DJFMDCDRMC. Arthritis in Black and White. Saunders. ISBN:1416055959. Read it at Google Books - Find it at Amazon
- 7. Thiele RG, Schlesinger N. Diagnosis of gout by ultrasound. Rheumatology (Oxford). 2007;46 (7): 1116-21. doi:10.1093/rheumatology/kem058 - Pubmed citation
- 8. Saffar P. Chondrocalcinosis of the wrist. Journal of hand surgery (Edinburgh, Scotland). 29 (5): 486-93. doi:10.1016/j.jhsb.2004.02.013 - Pubmed
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