Calcium pyrophosphate dihydrate deposition

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Calcium pyrophosphate dihydrate deposition (CPPD)/Pseudogout/ Pyrophosphate arthropathy/Chondrocalcinosis

Deposition of Ca2P2O2-2H2O crystals in synovium, articular cartilage and periarticular soft tissues  acute and chronic gout like attacks. M=F – usually around age 65+ (in 10-15%). Affects knees and wrist most commonly with tendency to not recur.

Terminology can be confusing – CPPD deposition is often referred to as chrondrocalcinosis. If CPPD crystals are deposited in joint  acute symptoms are often referred to as pseudogout.
Other calcium salts can also cause chrondrocalcinosis

Risk factors – aging, osteoarthritis, genetic defects, metabolic disorders
Associated with – gout, diabetes mellitus, hyperparathyroidism, amyloidosis, hypothyroidism, haemochromatosis, hypophosphatasia, hypomagnesaemia, osteoarthritis, benign hypermobility

Crystals deposited in joint  phagocytosied by leucocytes  release of lysosomal enzymes, cytokines, other mediators  acute/intense inflammatory response in joint.

Clinical features:
Variable clinical presentations and course.
Several clinical patterns:
1) Acute pseudogout – sudden onset of joint pain with erythema and swelling due to synovitis; limited motion; warm; effusion; tenderness – commonest cause of acute monoarthritis in elderly - knee more commonly involved – polyarticular attacks are rare – changes in talonavicular joint may be seen. No significant first MPJ involvement or erosions. Attacks last several days to several weeks – may have been precipitated by trauma, illness (eg myocardial infarction) or surgery. Diagnosis is usually by joint aspiration.
2) Pseudorheumatoid arthritis – chronic deforming polyarticular inflammation due to synovitis – also some develop systemic symptoms of malaise, fever, fatigue and morning stiffness
3) Psuedoosteoarthritis – most common pattern - symptoms and x-rays appear similar to osteoarthritis. May have been preceded by acute attacks of pseudogout.
4) Asymptomatic chrondocalcinosis – found on x-ray – no symptoms – present in up to 50% of those >80yrs. Treatment not needed.
5) Pseudoneuropathic joints – CPPD crystals can be found in those with Charcot’s neuroarthropathic joints  bony collapse and fragmentation. Mostly in females. Usually shoulder, hip and knee.

X-ray:
Calcification of articular and periarticular tissues; bilateral joint space narrowing, bone sclerosis, cyst formation.

Laboratory tests:
No specific biochemical abnormality. Crystals seen in synovial fluid with polarised light microscopy.

Differential diagnosis – gout, rheumatoid arthritis, septic arthritis, hydroxyapatite deposition
There may be a simultaneous gout and pseudogout – diagnosed with polarised light microscopy.

Treatment:
Joint aspiration to remove most of crystals (a diagnostic aspiration may halt attack).
Intra-articular corticosteroids
NSAID’s
Rest joint during acute attack
No treatment is known to prevent CPPD deposition in tissues

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