Calcium pyrophosphate dihydrate deposition disease
Updates to Article Attributes
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.
Terminology
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.
Pathology
The crystals are weakly positively birefringent on polarised microscopy and have a rhomboid or rod shape. Causes of CPPD can be divided into:
- idiopathic
- hereditary
- AD pattern; mutation in gene ANKH encoding transmembrane inorganic pyrophosphate transporter
- secondary
- haemochromatosis
- hyperparathyroidism
- hypothyroidism
- hypomagnesaemia 2
- previous joint injury
- ochronosis
Radiographic features
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)
- SLAC wrist can be seen in advanced cases
- a stepladder pattern of joint narrowing is classically described in which the narrowing is progressively less severe from the radiocarpal joint to the mid-carpal joint
- 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
- crowned dens syndrome: acute pain and systemic inflammatory syndrome 5
- intervertebral discs
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.
Differential diagnosis
Possible imaging differential considerations include
-
osteoarthritis
- usually have the typical weight-bearing distribution
-
giant cell tumour (GCT)
- subchondral cysts of CPPD can be large and simulate subchondral GCT
See also
-<li><a title="hypothyroidism " href="/articles/hypothyroidism">hypothyroidism </a></li>- +<li><a href="/articles/hypothyroidism">hypothyroidism </a></li>
References changed:
- 8. Saffar P. Chondrocalcinosis of the Wrist. J Hand Surg Br. 2004;29(5):486-93. <a href="https://doi.org/10.1016/j.jhsb.2004.02.013">doi:10.1016/j.jhsb.2004.02.013</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/15336755">Pubmed</a>
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