Familial deficiency of a plasma factor stimulating vascular prostacyclin activity

We previously reported successful treatment with plasma in patients with thrombotic microangiopathy and defective vascular PGI₂ activity and suggested that a defect in a plasma factor stimulating PGI₂ synthesis might be implicated in the pathogenesis. We report here that in one of these patients the plasma defect was still detectable one year after clinical remission (without recurrence). Two of this patient's four children had a similar, though less severe, plasma defect. The proposita is a 54-year-old woman with a clinical and laboratory picture of haemolytic uraemic syndrome. Unlike normal plasma, the patient's plasma had a low capacity to stimulate PGI₂ production by rat aortic rings (previously washed until their endogenous PGI₂ activity was exhausted). After plasma treatment the patient's plasma behaved normally in this respect, but again appeared deficient at out-patient follow-up. PGI₂ stimulating activity was normal in two daughters but consistently low (20-50% of control) in both patient's sons. None of them had any history or clinical signs of microangiopathic disorders. Detection of this plasma defect in apparently healthy subjects and in patients who have recovered from thrombotic microangiopathy episodes could have clinical implications.