Approach Considerations
A complete blood count (CBC) is indicated and usually shows lower platelets counts with elevated mean platelet volume. Thrombocytopenia is a frequent, but not invariable, finding in patients with Bernard-Soulier syndrome (BSS). Giant platelets are seen on the peripheral smear (see the image below), possibly exceeding the size of a red blood cell.
Peripheral smear of patient with Bernard-Soulier syndrome (BSS) showing giant platelets. These platelets are not counted as platelets in most particle counters.
Bleeding time is usually prolonged. The template bleeding time has largely been replaced by automatic platelet function analyzers (PFAs), such as the PFA-100.
Platelets do not aggregate in response to ristocetin. This is not corrected by the addition of normal plasma, as seen in von Willebrand disease. Platelets have normal aggregation in response to adenosine diphosphate (ADP), epinephrine, and collagen.
Flow cytometry can demonstrate abnormalities of platelet membrane glycoprotein.
A study by Bonnard et al indicated that assessment of both the immature platelet count and P-selectin expression could aid in distinguishing immune thrombocytopenia from inherited thrombocytopenia. A significantly lower immature platelet fraction was found in study patients with immune thrombocytopenia than in those with the inherited condition. On the other hand, there was significantly higher platelet activation in patients with immune thrombocytopenia, indicating greater P-selectin expression. [11]
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Peripheral smear of patient with Bernard-Soulier syndrome (BSS) showing giant platelets. These platelets are not counted as platelets in most particle counters.
