Editing Platelet (section)

==Clinical significance==
Spontaneous and excessive bleeding can occur because of platelet disorders. This bleeding can be caused by deficient numbers of platelets, dysfunctional platelets, or platelet densities over 1&nbsp;million/microliter. (The excessive numbers create a relative von Willebrand factor deficiency due to sequestration.)<ref>{{cite journal |vauthors=Murakawa M, Okamura T, Tsutsumi K, Tanoguchi S, Kamura T, Shibuya T, Harada M, Niho Y |date=1992 |title=Acquired von Willebrand's disease in association with essential thrombocythemia: regression following treatment |journal=Acta Haematologica |volume=87 |issue=1–2 |pages=83–87 |doi=10.1159/000204725 |pmid=1585777}}</ref><ref>{{cite journal |vauthors=van Genderen PJ, Leenknegt H, Michiels JJ, Budde U |date=September 1996 |title=Acquired von Willebrand disease in myeloproliferative disorders |journal=Leukemia & Lymphoma |volume=22 |issue=Suppl 1 |pages=79–82 |doi=10.3109/10428199609074364 |pmid=8951776}}</ref>

Bleeding due to a platelet disorder or a coagulation factor disorder can be distinguished by the characteristics and location of the bleeding.<ref name="Michelson" />{{rp|815, Table 39-4}} Platelet bleeding involves bleeding from a cut that is prompt and excessive, but can be controlled by pressure; spontaneous bleeding into the skin which causes a purplish stain named by its size: [[petechiae]], [[purpura]], [[ecchymoses]]; bleeding into mucous membranes causing bleeding gums, nose bleed, and gastrointestinal bleeding; menorrhagia; and intraretinal and intracranial bleeding.

Excessive numbers of platelets, and/or normal platelets responding to abnormal vessel walls, can result in [[venous thrombosis]] and [[arterial thrombosis]]. The symptoms depend on the thrombosis site.