Crystal-induced arthritis.

The identification of monosodium urate crystals in joint effusions of patients with gouty arthritis established that crystals can cause arthritis. Other crystals causing arthritis have also been identified, including calcium, pyrophosphate dihydrate (chondrocalcinosis, pseudo-gout), calcium hydroxapatite crystals (calcific periarthritis, acute arthritis) and depot corticosteroid crystals (which occasionally cause arthritis when injected intra-articularly.) Crystal-induced arthritis is characterized by acute articular inflammation although rarely causing joint destruction or permanent disability. It is important for clinicians because it can mimic more serious joint diseases like septic arthritis or even rheumatoid arthritis. It can be diagnosed with precision and in some types as in gout can be treated effectively. Also, it constitutes one of the best understood articular inflammatory processes and often is the first clinical clue for the presence of curable metabolic or endocrine diseases.