A common hematologic finding with variable clinical expression. A correct identification of the causes of thrombocytopenia is crucial for the appropriate management of these patients. However, platelet counts between 100 and150 x 109/L do not necessarily indicate disease if they have been stable for more than 6 months, and the adoption of a cut off value of 100 x109/L may be more appropriate to identify a pathologic condition. The relevance of thrombocytopenia in the individual patient is variable and depends on the clinical presentation.