Platelet Cyclo‐Oxygenase Deficiency in a Japanese

A case of platelet cyclo-oxygenase deficiency in a Japanese was investigated. There was a marked decrease of aggregation with collagen and absence of aggregation with epinephrine and arachidonic acid. The platelet response to a labile aggregation stimulating substance (LASS) was normal. There was no biosynthesis of prostaglandin endoperoxides from arachidonate. The platelets, including granular volume, showed no ultrastructural abnormalities. The responses to various inducers of platelet aggregation, except for arachidonate, were different from the cases described by others. It is concluded that the defective platelet function, due to a deficiency of platelet cyclo-oxygenase, is heterogeneous.