Serum and aqueous humor sialic acid levels in Behcet's disease. Serum and aqueous humor sialic acid (SA) levels were determined in 27 patients with Behcet's disease (Bd). Serum SA levels were elevated significantly during the active episode (mean, 113.4 +/- 4.12 mg/dl) and in the remission stages (mean, 85.4 +/- 4.79 mg/dl; P less than 0.001). A significant increase was also detected in active episodes when compared to chronic stages (P less than 0.02). Aqueous humor levels were also evaluated but could only be determined in the six eyes at the end-stage of the disease (mean, 2.65 +/- 0.60 mg/dl; P less than 0.05). 