Packed Cell Volume (PCV)

see Haematocrit HCT

Pancytopenia

A condition in which there are reduced numbers of all types of blood cells.

Paraprotein

A paraprotein is an abnormal protein similar to an antibody produced in certain conditions, for example in multiple myeloma. Its presence in the blood acts as an important marker of disease. Unlike normal antibodies, paraproteins do not fight infection.

Paroxysmal nocturnal haemoglobinuria (PNH)

A rare disorder characterised by an increased rate of break-down of red blood cells and decreased production of white blood cells and platelets. This leads to excretion of the red blood pigment, haemoglobin or chemicals produced when the body breaks down haemoglobin, in the urine. There may be thrombosis of veins. The cause is unknown and the severity of diseases variable. There is an association with aplastic anemia.

Pathogenesis

Development of a disease.

Pathologist

A doctor who specialises in the cause and diagnosis of disease and how disease affects the organs of a body.

Peripheral blood stem cell (PBSC)

Most blood-producing stem cells are found in the bone marrow. There are normally small numbers of stem cells in the circulation. These are known as peripheral blood stem cells.

Peripheral blood stem cell transplant

This is a stem cell transplant which uses stem cells collected from the blood rather than bone marrow .

Petechiae

Small red or purple pin-head spots on the skin. They are small haemorrhages and usually the result of a shortage of platelets.

Pharmacokinetics

The study of the action of a drug in the body over a period of time, including the processes of absorption, metabolism and excretion.

Phenotype

The characteristic appearance and function of a cell or tissue.

Philadelphia chromosome

An abnormal chromosome found in almost all cases of chronic myeloid leukaemia and in some cases of acute lymphoblastic leukaemia or other conditions. The Philadelphia chromosome is formed when part of chromosome 9 attaches to chromosome 22.

Plasma

The liquid part of the blood which is left when the cells have been removed but the blood has not been allowed to clot. The only difference between plasma and serum is that serum cannot form a clot. There are some blood tests which are normally done on serum and some on plasma.

Plasma cell leukaemia

The end stage of myeloma when immature plasma cells are found circulating in the blood.

Plasma cells

Large cells which develop from B lymphocytes and form antibodies. These are not normally found in circulating blood but are restricted to the bone marrow and lymph nodes.

Plasmacytoma

A solid tumour made up of myeloma cells, either in a bone or in the other tissues of the body. If there is only one such area, it is called solitary plasmacytoma. The key difference from myeloma is that plasmacytoma is localised with little or no involvement of bone marrow.

Plateau phase

Stable stage of disease in multiple myeloma following good response to anti-cancer treatment.

Platelets (Thrombocytes) (PLT)

are tiny cells produced by the bone marrow which are very important in preventing and controlling bleeding. They clump together to form a plug when bleeding occurs. They then release other chemicals that help the blood to clot and the blood vessel to heal.

Polycythemia rubra vera – PRV

A condition in which too many red blood cells are produced by the bone marrow. The total number of white blood cells and platelets may also be increased. The spleen is usually enlarged. How it is treated depends on the age of the patient and severity of the disease. This condition carries a small risk of developing into acute leukaemia.

Portacath™

A kind of central line in which the whole of the line is surgically implanted within the body, unlike a Hickman line™. A membrane just below the skin gives access by a simple skin puncture to a line running straight into one of the main blood vessels. This makes it easier to give chemotherapy.

Prognosis

The likely course of disease for a patient, particularly their chances of cure and complete recovery or length of survival.

Programmed Cell Death (PCD)

is death of a cell in any form, mediated by an intracellular program. PCD is carried out in a regulated process, which usually confers advantage during an organism’s life-cycle.

Prolymphocyte

An immature lymphocyte. Not commonly seen in the blood but in prolymphocytic leukaemia they may be present in large numbers.

Prolymphocytic Leukaemia (PLL)

A variant of chronic lymphocytic leukaemia (CLL) in which the malignant cells look more immature. The disease requires chemotherapy and/or radiotherapy and sometimes removal of the spleen (splenectomy).

Prophylaxis

Precautionary treatment given to prevent a disease occurring.

Protein

A protein is a long string of building blocks called amino acids. Most proteins are folded into complex shapes. Structural proteins are, in turn, the building blocks of which cells are made. There are also specialised proteins such as enzymes, which control the chemical reactions of the body, and antibodies.

Protocol

A schedule of treatment. For example, the number, frequency and timing of courses of anti-cancer drugs.

Pruritis

Itching, sometimes severe; this may be a significant problem in CLL.

Purging

The laboratory treatment of bone marrow harvested for an autologous bone marrow transplant or peripheral blood stem cell transplant to remove any remaining leukaemic cells so that there is less risk of relapse. The use of this procedure varies between treatment centres and depends on the type of leukaemia being treated.

Purine Analogue

are antimetabolites that mimic the structure of metabolic purines. Read more

Purpura

A condition characterised by the occurrence of purple spots on the skin, often accompanied by bleeding from the gums.