Wiskott—Aldrich Syndrome: Qualitative Platelet Defects and Short Platelet Survival

S ummary . Investigations of the haemostatic functions in three patients with the Wiskott-Aldrich syndrome are presented. All patients had severe thrombocytopenia and prolonged bleeding times. The platelets had abnormal morphology with reduced size and variations of shape. Electron microscopy revealed ultrastructural abnormalities with a reduced number of organelles, and many of the platelets contained large numbers of tubules. Platelet electrophoretic mobility in citrated plasma was not reduced by collagen, and platelet aggregation by collagen and ADP was deficient. Biochemical studies revealed a lack of the storage pool of adenine nucleotides. Platelet adhesiveness in vitro in whole blood was reduced. Platelet factor-3 release by kaolin, ADP and freezing and thawing was normal in one and reduced in another of the patients.
Platelet survival studies showed a normal survival time of normal donor platelets in one patient, while autologous platelets had a markedly reduced survival time in two of the patients. The bone marrow contained normal numbers of megakaryocytes. By electron microscopy of the bone marrow, blood platelets were found to be phagocytosed by macrophages and reticulum cells. The main cause of the thrombocytopenia is most probably incrcased peripheral destruction of platelets. It is suggested that the qualitatively defective platelets are recognized in the reticulo-endothelial system as foreign particles and phagocytosed.