A-Z of terminology

It can be confusing hearing lots of new and unfamiliar medical terms. Use our glossary for help in understanding more about MPNs.

Acute myeloid leukemia (AML)

Also known as acute myelogenous leukaemia or acute non- lymphocytic leukemia. A quickly progressive malignant disease in which there are too many immature blood forming cells in the blood and bone marrow, the cells being specifically those destined to give rise to types of white blood cells that fight infections.


A medical condition in which the red cells count or haemoglobin is less than normal.

Blood clot (or thrombus, or thrombosis)

Blood that has been converted from a liquid to a solid state; also called a thrombus. A blood clot is stationary within a vessel or the heart. If it moves from that location through the bloodstream, it is referred to as an embolus or embolism.

Blood Film

Blood is put on a slide so the cells can be observed using a microscope.

Blood transfusion

The transfer of blood or blood components from one person (the donor) into the bloodstream of another person (the recipient).  Often a life saving technique to replace blood cells or blood products lost through bleeding, or when your body can’’t make blood properly because of an illness such as some MPNs.

Bone marrow

Bone marrow is found inside many bones of the body.  In children, most bones are involved in the process of blood production, but as the body ages blood production is usually concentrated in the bones of the spine, sternum, rib, pelvis and small parts of the upper arm and leg.

Bone Marrow Aspirate

A sample of bone marrow (and sometimes a small ‘‘core’’ of bone) removed using a needle for study using a microscope.

Bone marrow transplant (BMT)

A procedure in which bone marrow that is diseased or damaged is replaced with healthy bone marrow. The bone marrow to be replaced may be deliberately destroyed by high doses of chemotherapy and/or radiation therapy.  The replacement marrow may be the patient’’s own marrow, treated, or it may come from another person (donor).


A gene which is mutated (changed) in about 30% of patients with ET or MF, mutations are sometimes referred to as type 1 or type 2.

Cannula / venflon

A small plastic tube inserted into a vein to give drugs, fluids or blood products to a patient.


Therapy for cancer using chemicals that stop the growth of cells.


A chronic condition is one that is long term in nature.  It comes from the Greek ‘‘chronos’’ and means lasting a long time.  MPNs are considered chronic conditions, and many symptoms of MPNs are also chronic.

Complete Blood Cell count (CBC)

A set values of the cellular (formed elements) of blood.  These measurements are determined by machines that analyse the different components of blood.  It is possible to take blood counts for each individual element of the blood, e.g. white blood cells, red blood cells, platelets, etc. 


An increase in the number of red blood cells in the body.


A hormone produced by the kidney that promotes the formation of red blood cells by the bone marrow.

Early satiety

Feeling full earlier than normal after eating usually caused by a large spleen.


A condition characterised by a lessened capacity for work, domestic and social activities, and reduced efficiency of accomplishment, usually accompanied by a feeling of weariness and tiredness.  Fatigue can be acute and come on suddenly or be chronic and persist.

Full Blood Count (FBC)

A blood test providing a breakdown of your red and white cells and your platelets.


White cells that fight off infections.  When MPN patients have elevated white blood cell levels, treatment with drugs like hydroxycarbamide or interferon can reduce the count.

Haematocrit (HCT)

Also known as Packed Cell Volume (PCV).  A measure of the thickness or viscosity of blood caused by excess red blood cells.


The oxygen-carrying pigment contained within red cells. Haemoglobin carries oxygen and carbon dioxide and contains iron.  People with too much haemoglobin are polycythaemic.  People with too little are anaemic.


A doctor who is specially trained in haematology [below].


The diagnosis, treatment, and prevention of diseases of the blood and bone marrow as well as of the immunologic, haemostatic (blood clotting) and vascular systems.


A form of anticoagulant used to treat or prevent clots and sometimes given in pregnancy.


An enlarged liver.

Imatinib(Glivec, STI 571)

Designer drug used to treat chronic myeloid leukaemiaand forms of MPNs. Under trial to treat myelofibrosis (MF).


JAK2 is molecule inside our cells that sends growth messages to the cell. Many MPN patients have a mutation or change in JAK2.

JAK2 V617F

Researchers in 2005 found a mutation (known as JAK2 V617F) in the JAK2 molecule in people with MPNs. The mutation affects the signalling performance of the JAK2 molecule.


Another term for white cells or granulocytes.

Low Molecular Weight Heparin

A form of anticoagulant used to treat or prevent clots and sometimes given in pregnancy.


This is a protein which is the receptor or docking station for the platelet hormone thrombopoietin.  The MPL gene can be mutated in patients with ET or MF. This was discovered in 2006. 


A condition in which the number of neutrophils (a type of white blood cell) in the bloodstream is decreased.


Removal of blood, can refer just to a test but also used to refer to a venesection.


Straw-coloured fluid through which our cells travel.


Platelets are sticky smaller cells that circulate in the blood.  Their function is to prevent bleeding when there has been an injury/cut to a blood vessel. When bleeding starts, platelets join together to form a clot which stops the flow of blood.

Platelet count

The calculated number of platelets [see above] in a volume of blood, usually expressed as platelets per cubic millimetre of whole blood. Normal platelet counts are in the range of 150,000 to 450,000 per microlitre (or 150 - 450 x 109 per litre).

Polycythaemia Vera

An increase in the number of red blood cells in the body.


Another word for itching. Pruritus can result from drug reaction, food allergy, kidney or liver disease, cancers, parasites, aging or dry skin, contact skin reaction, such as poison ivy, and for unknown reasons.

Red Blood Cells (RBCs)

Biconcave-shaped discs that contain haemaglobin, which carries oxygen and carbon dioxide to our bodies. Red blood cells survive for 120 days in the blood.

Saline drip

Salty water occasionally used in the vein to replace the fluid lost while having a venesection.  It is widely used for many other purposes and is known as a safe and versatile drug.


An organ located in the upper left part of the abdomen near the stomach.  The spleen produces lymphocytes (a type of white blood cell), filters blood, serves as a reservoir for blood, and destroys old blood cells.  The spleen can also supplement the bone marrow in the production of red blood cells in certain situations (as with MPNs).  This can sometimes lead to an enlarged spleen (splenomegaly).  An operation to remove the spleen is called a splenectomy.


A large spleen. 

Stem cells

Stem cells are cells that have the potential to develop into many different or specialised cell types.

Stroke(Cerebrovascular Accident or CVA)

The sudden death of some brain cells due to a lack of oxygen when the blood flow to the brain is impaired by blockage or rupture of an artery to the brain.


An abnormally high number of platelets in the blood, typically above 450,000 per microlitre.


A lower than normal number of platelets in the blood, typically below 150,000 per microlitre.


A high platelet count.


The formation or presence of a blood clot in a blood vessel.  The vessel may be any vein or artery.  The clot itself is termed a thrombus [see blood clot].


The removal of 450mls of blood from your arm as a treatment for too many red blood cells.  The method is the same as that of giving blood.  Also known as phlebotomy.


A tablet commonly used after a blood clot to thin the blood.

White Blood Cells (WBC)

There are five types of white blood cells: lymphocytes, monocytes, neutrophils, eosinophils and basophils. These cells are our body’’s defence against infection. There are far fewer white cells than red cells in our bodies.