Raised plasma levels of thromboxane B2 in systemic mastocytosis.

Plasma levels of thromboxane B2 and 6-keto-prostaglandin F1 alpha were measured in six patients with systemic mastocytosis. Patients with systemic mastocytosis had significantly higher plasma thromboxane B2 levels (530 +/- 105 pg/ml, mean +/- SEM) than controls (118 +/- 8.2 pg/ml, P less than 0.001) and significantly lower 6-keto-prostaglandin F1 alpha levels (40 +/- 3.1 pg/ml, mean +/- SEM) than controls (49 +/- 1.6 pg/ml, P less than 0.05). The mechanism of the raised plasma thromboxane B2 levels is not clear. One possible explanation is that the high thromboxane levels are secondary to an increased production of leukotrienes C and D, which are constituents of slow reacting substances of anaphylaxis.