Pseudogout (Calcium Pyrophosphate Dihydrate)
- Autoinflammatory disease triggered by calcium pyrophosphate dihydrate (CPPD) crystal deposition within joints
- One of many diseases associated with pathologic deposition of crystal; mineralization and ossification
- CPPD crystal deposition = chondrocalcinosis (calcification of hyaline or fibrocartilage), pseudogout, and pyrophosphate arthropathy
- Monosodium urate crystal deposition = gout
- Hydroxyapatite deposition = ankylosing spondylitis, osteoarthritis, and vascular calcification
- Suspect pseudogout with arthritis and a pattern of joint involvement inconsistent with degenerative joint disease (e.g., metacarpophalangeal joints, wrists).
- Clinical presentation is broad:
- Asymptomatic CPPD (incidentally identified on radiograph with or without additional findings of osteoarthritis)
- Acute CPPD arthritis (acute onset, self-limiting, synovitis)
- Knee is affected in >50% of all acute attacks versus MTP in gout.
- Can be brought on my trauma, medical illness, or surgery (after parathyroidectomy) (1)
- Chronic CPPD crystal inflammatory arthritis (2)[C]
- Chronic CPPD crystal deposition may cause a progressive degenerative arthritis in numerous joints; usually large joints; primarily in elderly patients
- Symptom onset is usually insidious.
- Definitive diagnosis requires the identification of CPPD crystals in synovial fluid.
- System(s) affected: endocrine/metabolic; musculoskeletal
- Synonyms: pseudogout; CPPD; pyrophosphate arthropathy; chondrocalcinosis
- Thought to affect 4–7% of adults in Europe and United States; 80% of patients >60 years
- No gender predominance. Men more likely to present acutely; women more likely to present atypically
- Chondrocalcinosis present in 1:10 adults age 60 to 75 years,1:3 age >80 years; only a small percentage develop arthropathy.
Etiology and Pathophysiology
- Arthropathy results from an acute autoinflammatory reaction to CPPD crystals in the synovial cavity.
- CPPD crystal deposition occurs in three stages:
Most cases are sporadic; rare familial pattern with autosomal dominant inheritance (<1% of patients). Mutation in ANKH gene increases risk for calcium crystal formation.
Advanced age; joint trauma
Colchicine 0.6 mg BID may be used prophylactically to reduce frequency of episodes in recurrent CPPD.
Commonly Associated Conditions
- Hemochromatosis; ochronosis
- Wilson disease
- Familial hypocalciuric hypercalcemia
- X-linked hypophosphatemic rickets
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