Noonan syndrome: coagulation and clinical aspects.

The study aims were to review the clinical features of a group of patients with Noonan syndrome and to further elucidate their bleeding tendency. Eighteen patients (12M, 6F) aged 2.6-13.3 years underwent a clinical assessment, a questionnaire of their bleeding tendency and laboratory coagulation studies. Nine had cyanotic spells or breathing difficulties after birth; 11 had poor feeding or weight gain. Increased bruising or bleeding was reported in 12 (67%), four of whom had bleeding from the oral cavity. Excessive bleeding was not reported from operative procedures in other sites. Partial thromboplastin time was prolonged in 10 (56%) associated with low levels of clotting factors, particularly XI and XII. Bleeding times were normal; one had marginal thrombocytopenia. Coagulation results did not correlate with bruising history and may not predict bleeding risk. Care is required when Noonan syndrome patients undergo surgery, particularly of the oropharynx, with immediate availability of suitable blood products.