Rare bleeding disorders: diagnosis of platelet function disorder

Platelets are critical for hemostasis and genetic defects involving platelet functions result in symptomatic bleeding of varying severities. In contrast to platelet quantitative disorders, qualitative platelet disorders are relatively rare and are difficult to diagnose, especially in patients with mild bleeding symptoms due to their lack of specificity for platelet dysfunction. In addition, the lack of standard platelet function tests makes it difficult for physicians to clinically distinguish patients from healthy subjects and, on occasion, the cause of bleeding symptoms remains unspecified. Resting platelets in the circulation become activated for thrombus formation at the site of vascular injury. Thrombus formation consists of platelet adhesion, granule secretion, and aggregate formation. An abnormality in any of the steps of thrombus formation has the potential to cause platelet dysfunction and bleeding symptoms. Understanding the mechanism of thrombus formation and the laboratory tests for evaluation of each step is important for properly diagnosing platelet function disorders.