Crystal arthritis: contemporary approaches to diseases of antiquity.

within articular and periarticular tissues are among the most common causes of acute mono/polyarthritis and, less frequently, chronic arthritis. The two most common types of microcrystal synovitis are those associated with: • monosodium urate monohydrate (MSUM): gout • calcium pyrophosphate dihydrate (CPPD): pseudogout. These arthritides are frequently encountered in medical inpatients in whom intercurrent illness and dehydration may trigger attacks. Other rarer forms of microcrystal arthritis are also recognised (oxalate and hydroxyapatite) but are beyond the scope of this article.