The plasma concentration of activated protein C appears normal in patients with haemophilia

Summary.  Increased concentration of activated protein C (APC) has been observed in patients with thromboembolic disorders, but whether the level of APC in patients with bleeding disorders is decreased remains unknown. Seventy patients with haemophilia A or B with mild, moderate or severe form were studied. Detailed information on bleeding, arthropathy and factor consumption was collected during a 10‐year period. The clinical severity of the disease was expressed as the Hemophilia Severity Score (HSS). Plasma concentration of APC was measured as APC in complex with protein C inhibitor. The median concentration of APC‐PCI complex in patients with haemophilia was 0.14 μg L−1 and it did not differ between the types and forms. In 16 patients with severe haemophilia A and the inversion mutation in intron 22, there was no correlation between clinical severity and the concentration of APC‐PCI complex. Patients with haemophilia appear to generate normal concentrations of APC during basal conditions. APC does not seem to be an important modulator of the phenotypic expression of haemophilia.

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