July 17, 2024 Blood is made up of plasma, red blood cells, white blood cells and platelets. Sometimes platelets are referred as blood cells, but they are not cells. Instead they are fragments of other cells, the megakaryocytes. Platelets and megakaryocytes are produced in the bone marrow and each megakaryocyte gives rise to thousands of platelets that are released into the blood or stored in the spleen, depending on needs. An adult produces an average of 150-400 thousand platelets per mL of blood per day and these have an average lifespan of 7-10 days. Functions of platelets The main function of platelets is related to hemostasis , that is, the body response to bleeding. Platelets intervene in the first phase of the process, or primary hemostasis. When platelets intervention is necessary, they go to the site of the injured vessel and change their shape, starting to resemble spheres from which filaments emerge which facilitate adhesion and promote movement of more platelets forming the platelet plug . In the later stages of clotting, other substances and cells will help form a stable clot to prevent bleeding until the vessel has healed. Platelet disorders Platelet disorders may be due to: A problem with the platelets themselves; Being a consequence of another disease. There are several situations and diseases that cause changes in platelets, some genetically transmitted, others acquired, and of varying severity. Platelet changes can be: Quantitative, that is, related to the number of platelets. Depending on the cause, the body may: Produce excess platelets; Produce few platelets; Use or destroy platelets faster than they are replaced. Qualitative, in which the number of platelets is within normal limits, but the functions are not performed correctly. In any case, there will be consequences related to blood clotting. Platelets number deviations Thrombocytosis (or thrombocythemia) and thrombocytopenia are deviations in the number of platelets. In an adult, the reference value for the number of platelets is 170-430 x 10 9 /L. Thrombocytosis or thrombocythemia is the increase in the number of platelets in the blood to values above the normal limit. Thrombocytopenia is the decrease in the number of platelets below the normal limit. Platelets number increase Primary or essential thrombocythemia is hereditary and is due to gene mutations. Reactive thrombocytosis or secondary thrombocythemia is an increase in platelets resulting from other diseases or problems, including: Anemia Some cancers: lung, digestive, breast, ovarian, lymphoma Splenectomy (removal of the spleen) Some chronic inflammatory and infectious diseases, like rheumatoid arthritis, inflammatory bowel disease or tuberculosis, as well as acute infections and other. When there is an increase in the number of platelets, blood clots can form more easily (hypercoagulation) and there may be an increased risk of: Acute myocardial infarction Stroke Deep vein thrombosis and pulmonary embolism Platelets number decrease When there is thrombocytopenia, there may be a greater risk of bleeding , with possible complications such as: Gums and nose bleeding; Prolonged menstruation; Bruising easily; Presence of red spots on the skin; Fatigue. Examples of diseases related to thrombocytopenia are: Hemophilia Von Villebrand disease Hereditary thrombocytopenia Immune-mediated thrombocytopenia Thrombotic thrombocytopenic purpura Remember : There may be deviations from normal platelet values that are transient and have no serious significance , such as those related to the menstrual cycle; It is not possible to draw any definitive conclusions solely from the results of a platelet count; Platelet count results, like any other medical test, must be interpreted in the context of each patient situation and with the results of medical evaluation and other tests. Sources Kutter DJ. Overview of platelet disorders . MSD Manual. National Heart, Lung and Blood Institute. What Are Platelet Disorders? Williams O, Sergent SR. Histology, Platelets . Treasure Island: StatPearls Publishing; 2024. The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
