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Three family members from two successive generations showed a moderate bleeding disorder. The bleeding times (Duke and Ivy-Borchgrevink) were both constantly prolonged. Platelet aggregation induced by ADP and adrenaline showed no second wave; collagen at low to moderate concentrations failed to aggregate and release ATP whereas higher amounts aggregated and released. Aggregation and release due to thrombin, ristocetin and synthetic epoxy derivatives (U 44069 and U 46619) were normal. Arachidonate (A.A.) was inactive and was not converted into thromboxane (TX) A2 activity evaluated on the rabbit aorta strip. The patient’s platelets did not respond to A.A. when PRP from an aspirin treated control was added. Platelet phospholipids (PL) were labelled by 14C - A.A. before stimulation by thrombin (T). Radioactivity of the PL of the propositus' platelets was affected with T to a similar extent as 5 laboratory controls, indicating that the phospholipase activity was not impaired. In contrast, no TXB2 was found: 0.9 p. cent as compared to 6 p. cent of total radioactivity in controls.  Our data suggest a deficit in cyclo-oxygenase particularly since the levels of PGE2, PGF2a and PGD2 were within the limits of detection. These results seem to rule out the possibility of a TX-synthetase deficiency with excessive production of anti-aggregating PGs. This study suggests that transmission is autosomal dominant and confirms that cyclo-oxygenase is not needed for aggregation and ATP-release by high amounts of collagen.

Familial And Constitutional Moderate Bleeding Disorder Associated With Defective Platelet Cyclo-Oxygenase