A patient presents with easy bruising, petechiae, and a prolonged bleeding time, but a normal prothrombin time and partial thromboplastin time. Which of the following coagulation disorders is most likely responsible for these symptoms?

Platelet function disorders, such as Bernard-Soulier syndrome or Glanzmann thrombasthenia, can cause easy bruising, petechiae, and a prolonged bleeding time due to impaired platelet aggregation or adhesion, despite normal coagulation factor levels.