PLATELET DYSFUNCTION IN NOONANS SYNDROME - A CASE WITH A PLATELET CYCLOOXYGENASE-LIKE DEFICIENCY AND CHRONIC IDIOPATHIC THROMBOCYTOPENIC PURPURA

Individuals with Noonan's syndrome are likely to have one or more coagulation abnormalities: complex platelet function defects, partial Factor XI deficiency, or von Willebrand's disease. A distinctive platelet function defect has not been identified. The authors describe a 24-year-old woman with Noonan's syndrome, chronic idiopathic thrombocytopenic purpura (ITP), and a platelet function defect characterized by a > 15-minute bleeding time, failure of aggregation and release with 10 mu-M ADP, 10-mu-M epinephrine, 750-mu-M arachidonic acid or 0.019 g/L collagen. A mixture of aspirin-treated platelets with the patient's platelets failed to correct the defect. Addition of 2.5-mu-M U46619 (a PGG2 analogue) corrected the aggregation and release defect. An electron microscopic analysis failed to reveal structural abnormalities. Thus, the platelet function defect in this patient appears to be a functional deficiency of cyclooxygenase. The presence of autoantiplatelet antibodies in a clinical setting consistent with chronic ITP raises the possibility that the defect may be acquired.