Hemorrhagic syndromes are investigated using algorithms established by reference centers and hemostasis societies.

The investigation of platelet dense granules (nucleotide and serotonin testing) is part of the second-line tests.

It can be performed in cases of platelet aggregation abnormalities in platelet-rich plasma (PRP) suggesting a secretion abnormality, or in cases where the latter is normal, it can be performed if the patient's clinical presentation points to a primary hemostasis abnormality and the clinician wishes to pursue further investigations Intraplatelet serotonin deficiencies are often iatrogenic and may be accompanied by bleeding.

Their impact on platelet function is poorly documented.

Inclusion Criteria:

• Adult patient (≥ 18 years old)
• Treated at Strasbourg University Hospital for a hemorrhagic syndrome, suggesting a primary hemostasis abnormality and normal von Willebrand factor, during the period from January 1, 2023, to April 1, 2024.

Exclusion Criteria:

- Refusal to participate in the study

Adult patient (≥ 18 years old) treated at Strasbourg University Hospital for a hemorrhagic syndrome, suggesting a primary hemostasis abnormality and normal von Willebrand factor, during the period from January 1, 2023, to April 1, 2024.