Urate spherulites in gouty synovia.

We have identified urate crystals in gouty synovial fluid in a spherulite form. Studies in vitro established these "beachball" structures as chemically identical to classic "needles" of monosodium urate monohydrate, the prime factor in gouty arthritis. Previously described in the 1890s by a German scientist, these structures have not been recognized by clinicians examining fluid from arthritic joints. We suggest an identification scheme for beach ball-like" structures in synovial fluid.