Cholesterol crystals in synovial and bursal fluid.

Cholesterol crystals were found in two patients with classic rheumatoid arthritis (RA). In one patient, cholesterol crystals were found in synovial fluid from both shoulder joints, and in the second they were in an olecranon bursa. To examine the possible systemic etiology of cholesterol crystals in synovial and bursal fluid, lipid concentrations and the presence of serum antilipoprotein antibodies were measured. Antilipoprotein antibodies were not found. The concentration of lipid and lipoproteins, as well as the normal pattern of lipoprotein on agarose gel, eliminates the possibility of hyperlipoproteinemia. Results seemed to exclude a systemic etiology for the formation of cholesterol crystals in synovial and bursal fluid in the RA patients. It appears that several local factors such as defective drainage, local destruction, increased permeability of synovial membrane, and intraarticular (bursal) bleeding are possible etiologies.