Bleeding disorders in Noonan syndrome: three case reports and review of the literature.

Purpose: Noonan syndrome (NS) is a congenital disorder characterized by various phenotypic features and congenital anomalies. Bleeding disorders are among the more serious, common, yet poorly defined complications associated with NS. As a means of focusing on these complications, we report three patients with stigmata of NS, each of whom had a combination of different hemostatic disorders, and review the literature on bleeding disorders in NS.
Patients and Methods: The clinical course and hemostatic abnormalities in three patients with NS were studied, and a literature review on NS was undertaken.
Results: The three patients we report had decreased coagulation factor levels (factors XI and II), von Willebrand disease, various levels of thrombocytopenia, and abnormal platelet function. The literature review on NS discloses multiple types of hemostatic abnormalities and a wide range of clinical presentations. A low level of coagulation factor XI is the most frequently described; thrombocytopenia and abnormal platelet function are also common.
Conclusions: The existence of various types of bleeding disorders within one syndrome is unusual and requires further investigation. Recognition of this common complication in children with NS would aid both clinical management and understanding of the spectrum, the frequency, and perhaps even the basis of the hemostatic defects in this syndrome. We recommend performing coagulation screening tests in every patient with NS.