[Differential diagnosis of platelet disorders]

Platelet disorders frequently represent a cause of bleeding disorders with a late manifestation and spontaneous bleeding. Disturbances of cellular hemostasis can be of quantitative nature due to an altered production or destruction of platelets. Qualitative disturbances can be associated with defects of adhesion, secretion or degranulation. Drug induced reactions, inflammatory processes and autoimmune reactions are the most frequent underlying disorders. Even a late manifestation, however, does not exclude congenital disorders. In the differential diagnosis of thrombocyte disorders the anamnestic analysis of the clinical circumstances of manifestation, of a family background and potentially interfering drugs are of central importance. Template bleeding time, aggregometry and flow cytometry are complementary methods for the characterization of functional defects. First of all, a von Willebrand syndrome as the most frequent congenital form of a mucocutaneous bleeding pattern needs to be excluded. The clinical context is very important in the analysis of disturbances of platelet turnover. Reticulated platelets allow the quantitative assessment of reduced production or increased destruction. Platelet indices, morphological assessment of blood and bone marrow and immunological tests allow the pathogenetical classification of thrombocytopenia. Idiopathic thrombocytopenia (ITP) is a frequent diagnosis by exclusion. The analysis of glycoprotein expression and the genetic characterization of suspected congenital defects are only performed in selected cases. Clinical and laboratory assessment are complementary in the discrimination of secondary forms of thrombosis from clinically relevant clonal disturbances.