Which type of arthritis is defined by uric acid crystal deposition causing joint inflammation?

• A. Gout
• B. Pseudogout
• C. Rheumatoid arthritis
• D. Osteoarthritis

Answer: (A)

Arthritis caused by deposition of monosodium urate crystals in the joint triggers an intense inflammatory response, which is the hallmark of gout. The crystals are needle-shaped and negatively birefringent under polarized light, and they often accumulate in a joint like the big toe, causing abrupt, severe pain with redness and swelling. This crystal-driven mechanism differentiates gout from other inflammatory or degenerative arthritides. Pseudogout involves calcium pyrophosphate crystals that are rhomboid-shaped and positively birefringent, rheumatoid arthritis is autoimmune with symmetric joint involvement and autoantibodies, and osteoarthritis is a wear-and-tear degeneration without crystal deposition. Recognizing the urate crystal deposition helps explain both the clinical presentation and the treatments aimed at lowering uric acid and reducing acute inflammation.