Words to know: MDS and MPN (bone marrow disorders)
- Bone marrow
- The soft tissue inside bones where blood cells are made.
- Stem cell
- A young cell in the marrow that can grow into any type of blood cell.
- MDS (myelodysplastic syndromes)
- Conditions where the marrow makes blood cells that do not grow up properly, leading to low blood counts.
- MPN (myeloproliferative neoplasms)
- Conditions where the marrow makes too many of one or more types of blood cells.
- Polycythemia vera (PV)
- An MPN where the marrow makes too many red blood cells.
- Essential thrombocythemia (ET)
- An MPN where the marrow makes too many platelets.
- Myelofibrosis
- A condition where scar tissue builds up in the marrow and the spleen often gets bigger.
- AML (acute myeloid leukemia)
- A fast-growing blood cancer that MDS or MPN can sometimes turn into.
- Blasts
- Very young, immature blood cells. More blasts in the marrow can mean more serious disease.
- Anemia
- Too few red blood cells, which can cause tiredness and shortness of breath.
- Platelets
- Small blood cells that help blood clot and stop bleeding.
- Hematocrit
- The percent of your blood made up of red blood cells.
- Phlebotomy
- Removing some blood from a vein, like donating blood, to thin the blood.
- Spleen
- An organ on the upper left side of the belly that filters blood. It can grow large in MPN.
- JAK2
- A gene that, when changed, causes most cases of MPN.
- Risk score
- A tool that combines test results to estimate how a condition may behave.
- Transfusion
- Getting red blood cells or platelets from a donor through an IV.
- Iron overload
- Too much iron in the body, often from many transfusions.
- Iron chelator
- A medicine that removes extra iron from the body.
- Hypomethylating agent
- A type of medicine, such as azacitidine or decitabine, that helps the marrow work better in MDS.
- JAK inhibitor
- A pill that blocks the overactive JAK signal in MPN, such as ruxolitinib.
- Allogeneic stem cell transplant
- Replacing your marrow with healthy stem cells from a donor. It can cure some people.
- Cytoreduction
- Using medicine to lower high blood counts.
- Clone
- A group of cells that all came from one changed cell.
Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.