Deposition of calcium pyrophosphate dihydrate crystals in joint cartilage leading to inflammatory arthritis. Manifestations range from asymptomatic chondrocalcinosis on imaging to acute pseudogout flares or chronic degenerative arthropathy.
Common crystal arthritis in older adults (nearly 50% of people >85 have radiographic CPPD). Often mimics gout or septic arthritis, so misdiagnosis can occur unless CPP crystals are identified. Recognizing pseudogout also prompts evaluation for treatable causes (e.g., hemochromatosis, hyperparathyroidism).
Acute pseudogout (CPP crystal arthritis): sudden onset of intense pain, redness, warmth, and swelling in a joint (classically the knee). Attacks last days–weeks and may be precipitated by trauma, surgery, or severe illness.
Chronic CPPD arthropathy: a progressive degenerative joint disease that can resemble osteoarthritis (cartilage calcification and joint space loss) or even pseudo–rheumatoid arthritis (waxing-waning inflammation in multiple joints, e.g. wrists/MCPs). Often coexists with osteoarthritis in affected joints.
Asymptomatic chondrocalcinosis: many patients (especially elderly) have calcification of cartilage on X-ray with no acute arthritis. This radiographic finding can precede or accompany symptomatic CPPD disease.
Always perform arthrocentesis for a new inflamed joint to analyze synovial fluid: look for CPPD crystals and exclude infection. Under polarized light, CPP crystals are rhomboid and show weakly positive birefringence.
Differentiate CPPD from gout crystals: CPP crystals are rhomboid and blue when Parallel to compensator (weak positive birefringence), whereas gout's urate crystals are needle-shaped and turn yellow when Parallel (negative birefringence).
Check for chondrocalcinosis on imaging: X-rays often show linear calcifications in articular cartilage (e.g., meniscus or wrist cartilage). Note that finding chondrocalcinosis alone doesn't confirm symptoms are from CPPD, but it supports the diagnosis in context.
If pseudogout is confirmed, screen for underlying disorders that predispose to CPPD: e.g., measure calcium (for hyperparathyroidism), iron studies (for hemochromatosis), magnesium (hypomagnesemia), etc. Treating the underlying metabolic issue may reduce CPPD attacks.
degenerative joint disease; chronic pain without acute crystal flares (though OA changes often accompany CPPD)
Acute attack: relieve inflammation with NSAIDs (if no contraindications), colchicine, and/or glucocorticoids. Often the joint is aspirated for relief and a corticosteroid is injected. Severe or refractory cases may benefit from an IL-1 inhibitor (anakinra).
Prevention: for frequent flares, consider daily low-dose colchicine or NSAIDs to reduce attack frequency. If needed, some patients require low-dose oral prednisone for chronic suppression.
Manage chronic CPPD arthropathy similar to osteoarthritis (exercise, physical therapy, analgesics) since no treatment can dissolve CPP crystals or reverse cartilage calcification.
Birefringence tip: Blue when Parallel = Pseudogout, Yellow when Parallel = gout.
Think of metabolic associations: elderly patient with hemochromatosis or hyperparathyroidism + knee arthritis → suspect pseudogout.
If joint fluid shows very high WBC or patient has high fever, don't assume it's "just pseudogout" – always rule out septic arthritis (crystals can co-exist with infection).
Older patient with acute monoarthritis (e.g., knee) → arthrocentesis for synovial fluid analysis (crystals & culture).
If fluid shows rhomboid, positively birefringent CPP crystals and no infection → diagnose pseudogout (acute CPP crystal arthritis).
Treat acute pseudogout with NSAIDs (first-line if tolerated), colchicine, and/or corticosteroids (consider joint aspiration + intra-articular steroid).
After acute flare, evaluate for secondary causes of CPPD (check Ca²⁺/PTH, iron studies, Mg²⁺, etc.) and manage those conditions.
Frequent flares → initiate prophylaxis (daily colchicine or NSAID); manage chronic CPPD joint damage with OA measures (weight loss, PT, analgesics).
Elderly patient (≥65) with an acutely swollen, red knee (± low-grade fever); synovial fluid shows rhomboid, positively birefringent crystals and no organisms on Gram stain → pseudogout (acute CPP crystal arthritis).
Middle-aged man with bronze diabetes (hereditary hemochromatosis) develops recurrent knee and wrist pain; X-ray reveals cartilage calcifications (chondrocalcinosis) → pseudogout due to CPPD deposition from iron overload.
Case 1
A 78‑year‑old woman with a history of hypertension presents with acute onset of right knee pain, swelling, and redness.
Case 2
A 55‑year‑old man with hereditary hemochromatosis (skin bronzing, diabetes) reports chronic joint stiffness and episodic swelling in his wrists and knees.
Polarized light microscopy of synovial fluid showing blue (parallel) and yellow (perpendicular) CPP crystals.
