From the Guidelines
Gout and pseudogout are distinct conditions with different underlying causes, clinical presentations, and treatment approaches, with gout resulting from monosodium urate crystal deposits and pseudogout involving calcium pyrophosphate crystals. The key differences between gout and pseudogout can be summarized as follows:
- Cause: Gout is caused by excess urate crystals accumulating in body tissues and fluid, resulting in inflammatory arthritis 1, whereas pseudogout is caused by calcium pyrophosphate crystals.
- Clinical presentation: Gout typically affects the big toe first (podagra) and other lower extremity joints, whereas pseudogout more commonly targets larger joints like knees, wrists, and shoulders.
- Crystal characteristics: Under microscopic examination, gout crystals appear needle-shaped and negatively birefringent, while pseudogout crystals are rhomboid-shaped and weakly positively birefringent.
- Treatment: Gout is managed with medications like colchicine, NSAIDs, and long-term urate-lowering therapies such as allopurinol or febuxostat, while pseudogout treatment focuses primarily on symptom relief with NSAIDs, colchicine, or joint injections without specific crystal-preventing medications.
- Associated factors: Gout is strongly associated with diet, alcohol consumption, and metabolic syndrome, whereas pseudogout is more commonly linked to aging, osteoarthritis, and metabolic conditions like hyperparathyroidism. It is essential to correctly diagnose gout and differentiate it from other inflammatory arthritic conditions, such as rheumatoid arthritis, septic arthritis, and inflammatory episodes of osteoarthritis, as treatment of these conditions differs 1. The reference standard for diagnosing acute gout is joint aspiration with synovial fluid analysis for MSU, which can help distinguish it from pseudogout and other conditions 1.
From the Research
Key Differences Between Gout and Pseudogout
- Gout is characterized by the deposition of monosodium urate (MSU) crystals in the joints and soft tissues, while pseudogout is caused by calcium pyrophosphate dihydrate (CPPD) crystals 2, 3, 4, 5.
- The clinical presentation of gout typically involves a sudden onset of intense pain, mostly affecting the big toe, foot, ankle, and knee, whereas pseudogout can present as acute mono- or oligoarticular disease, or as a chronic polyarthropathy resembling osteoarthritis or rheumatoid arthritis 2, 3.
- Gout is often associated with hyperuricemia, and patients with gout may develop urinary tract stones and interstitial urate nephropathy 2.
- Pseudogout, on the other hand, is more commonly seen in older adults and can be associated with osteoarthritis, particularly in atypical distributions 3.
- The diagnosis of gout and pseudogout can be confirmed by the presence of characteristic crystals in the joint fluid, with MSU crystals appearing needle-like and showing strong negative birefringence by polarized microscopy, and CPPD crystals being smaller and showing weaker birefringence 2, 4, 5.
Risk Factors and Clinical Features
- A study found that gout patients were younger, had higher BMI, and had a higher prevalence of below-knee arthritis compared to pseudogout patients 6.
- Hyperuricemia during acute arthritis was found to be a characteristic of gout, while monoarticular attack and periarticular soft tissue swelling were indications for pseudogout 6.
- The management of gout and pseudogout includes the use of nonsteroidal anti-inflammatory drugs, colchicine, or corticosteroids, as well as uric acid-lowering agents for refractory or chronic tophaceous disease 2, 3, 4.