- Calcium pyrophosphate dihydrate (CPPD) crystal deposition disease can mimic gout, rheumatoid arthritis, or osteoarthritis.
- Pseudogout causes an intermittent monoarthritis, often of the knee or wrist.
- Diagnosis of pseudogout established by demonstrating CPPD crystals in joint fluid.
- CPPD crystal deposition disease is associated with other diseases, especially hemochromatosis and hyperparathyroidism.
Calcium pyrophosphate dihydrate (CPPD) deposition disease can be asymptomatic or may result in a variety of clinical presentations (Table 45–1). Although the term “pseudogout” is often used to represent the entire spectrum of CPPD, it accurately describes the acute gout-like attacks of inflammation that occur in some patients with CPPD crystal deposition disease. In fact, the name pseudogout was coined when it was discovered that a subset of patients believed to have gout actually had CPPD crystals in their synovial fluid, instead of uric crystals. CPPD deposition may give rise to clinical presentations that mimic septic arthritis, polyarticular inflammatory arthritis, or osteoarthritis (Table 45–1). In addition, CPPD crystals may coexist in synovial fluid with urate or basic calcium phosphate crystals in inflammatory and osteoarthritic-like diseases, as well as in Charcot joints.
Table 45–1. Conditions that May Mimic CPPD Crystal Deposition Disease. |Favorite Table|Download (.pdf)
Table 45–1. Conditions that May Mimic CPPD Crystal Deposition Disease.
- Septic arthritis
- Rheumatoid arthritis
Although the cause of CPPD crystal deposition is unknown, recent identification of mutations in the ANKH gene on chromosome 5p has been associated with familial chondrocalcinosis, probably through disordered inorganic pyrophosphate (PPi) transport mechanisms. Low ratios of inorganic phosphate (Pi) to inorganic pyrophosphate (PPi) favor CPPD crystal deposition in joints. Research also shows that the immune system may influence the development of pseudogout, through the secretion of interleukin-1 and other cytokines that facilitate local tissue inflammation.
Several risk factors for pseudogout have been identified. Perhaps the most important factor is aging. CPPD deposition will probably occur in everyone if they live long enough. Genetic factors also influence crystal formation, given that numerous familial cases of CPPD deposition have been described in many nationalities. Interestingly, the pattern of clinical manifestation differs from family to family. For example, disease may occur in some families at an early age that mimics a spondyloarthropathy. In other families, presentation occurs in later years with sporadic joint distribution. What is notable is the prevalence of CPPD deposition is greater in people who have suffered orthopedic trauma; symptoms may persist despite attempts to repair affected joints. Finally, several metabolic and endocrine conditions have been associated with an increased frequency of CPPD disease, including hyperparathyroidism, hemochromatosis, hypothyroidism, amyloidosis, hypomagnesemia, acromegaly, and hypophosphatasia.
Approximately 25% of patients with CPPD deposition disease exhibit the pseudogout pattern of disease. Signs and symptoms are characterized by acute, typically monoarticular inflammatory arthritis lasting for several days to 2 weeks. These self-limited attacks may vary ...