pleiotropic Producing or having multiple effects from a single gene. For example, the Marfan gene is pleiotropic, potentially causing such diverse effects as long fingers and toes (arachnodactyly), dislocation of the lens of the eye, and dissecting aneurysm of the aorta.
platelet count The calculated number of platelets in a volume of blood, usually expressed as platelets per cubic millimeter (cmm) of whole blood. Platelets are the smallest cell-like structures in the blood and are important for blood clotting and plugging damaged blood vessels. Platelet counts are usually done by laboratory machines that also count other…
platelet An irregular, disc-shaped element of blood that assists in blood clotting. During normal blood clotting, platelets group together (aggregate). Although platelets are often classified as blood cells, they are actually fragments of large cells called megakaryocytes. Also known as thrombocyte. See also blood cell.
plastic surgery A surgical specialty that is dedicated to reconstruction of facial and body defects due to birth disorders, trauma, burns, and disease. Plastic surgery is also involved with the enhancement of the appearance of a person through cosmetic surgery.
plastic surgeon A surgeon who specializes in reducing scarring or disfigurement that may occur as a result of accidents, birth defects, or treatment for diseases, such as melanoma. Many plastic surgeons also perform cosmetic surgery that is unrelated to medical conditions.
Plasmodium The genus of the class of Sporazoa that includes the parasite that causes malaria. Plasmodium is a type of protozoa, a single-celled organism that is able to divide only within a host cell. The main types of Plasmodium are P. falciparum, the species that causes falciparum malaria, the most dangerous type of malaria; P….
plasmapheresis A procedure in which whole blood is taken from a person and separated into plasma and blood cells; the plasma is removed and replaced with another solution, such as saline solution, albumin, or specially prepared donor plasma; and the reconstituted solution is then returned to the patient. Plasmapheresis is used in the treatment of…
plasmacytoma Cancer of the plasma cells (white blood cells that produce antibodies) that may turn into multiple myeloma.
plasmacyte See plasma cell.
plasma donation The donation or sale of blood plasma for use in medical or other products. Unlike blood donors, most plasma donors in the US are paid. The procedure is done in a walk-in facility, where whole blood is taken through an IV needle and separated into plasma and blood cells. The blood cells are…
plasma cell A type of white blood cell that produces and secretes antibodies. A plasma cell is a fully differentiated, mature lymphocyte in the B cell lineage. As with most cell types, plasma cells can mutate to give rise to cancer. Plasma cell malignancies include plasmacytoma, multiple myeloma, Waldenstrom macroglobulinemia, and plasma cell leukemia. Also…
plasma The liquid part of the blood and lymphatic fluid, which makes up about half of the volume of blood. Plasma is devoid of cells and, unlike serum, has not clotted. Blood plasma contains antibodies and other proteins. It is taken from donors and made into medications for a variety of bloodrelated conditions.