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.
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.
Calcification of articular and periarticular tissues; bilateral joint space narrowing, bone sclerosis, cyst formation.
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.
Joint aspiration to remove most of crystals (a diagnostic aspiration may halt attack).
Rest joint during acute attack
No treatment is known to prevent CPPD deposition in tissues