Summary
Phylogenetically mammalian platelets are an apocrine secretion from nucleated thrombocytes,
and biologically the number of circulating fragments is irrelevant compared with their
total mass and biochemical function. The literature on human genetic derangements
affecting the circulating platelet mass is reviewed. The product of platelet count
and platelet volume is shown to be “canalised” since many congenital forms of thrombocytopenia
are associated with a reciprocal increase in the mean platelet volume. Considerations
of platelet size are essential since macrothrombocytopenia is a racial characteristic
of many Mediterranean peoples and probably also occurs frequently in others races.
The location of platelet disorders in relation to the phylogenetic canal provides
an objective classification which has diagnostic, therapeutic and prognostic significance.