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Noonan syndrome: partial factor XI deficiency
M de Haan1, J J vd Kamp, E Briët
1Department of Pediatrics, University Hospital Leiden, The Netherlands.
Among the multiple extracardiac abnormalities seen in the Noonan syndrome, several authors have mentioned an unexplained bleeding tendency. In 1983 Kitchens and Alexander reported on a partial deficiency of coagulation factor XI in four patients with Noonan syndrome. We examined 9 patients with Noonan syndrome and 9 of their 18 parents (3 of them also had Noonan syndrome). Four Noonan patients were found to have a partial deficiency of factor XI (30-65%). The Noonan patients had a mean factor XI level of 67%, significantly lower than the normal parents (mean level of 109%). Our study suggests a relationship between Noonan syndrome and a partial deficiency of factor XI.
Among the multiple extracardiac abnormalities seen in the Noonan syndrome, several authors have mentioned an unexplained bleeding tendency. In 1983 Kitchens and Alexander reported on a partial deficiency of coagulation factor XI in four patients with Noonan syndrome. We examined 9 patients with Noonan syndrome and 9 of their 18 parents (3 of them also had Noonan syndrome). Four Noonan patients were found to have a partial deficiency of factor XI (30-65%). The Noonan patients had a mean factor XI level of 67%, significantly lower than the normal parents (mean level of 109%). Our study suggests a relationship between Noonan syndrome and a partial deficiency of factor XI.