PNH occurs because of a genetic change in bone marrow bone marrow: The soft, spongy tissue inside most bones. Blood cells are formed in the bone marrow. stem cells stem cells: Cells in the body that develop into other cells. There are two main sources of stem cells. Embryonic stem cells come from human embryos and are used in medical research. Adult stem cells in the body repair and maintain the organ or tissue in which they are found. Blood-forming (hemapoietic) stem… . This creates a family of abnormal blood cells referred to as a PNH clone clone: To make copies. Bone marrow stem cells clone themselves all the time. The cloned stem cells eventually become mature blood cells that leave the bone marrow and enter the bloodstream. . These PNH blood cells lack a key protein that protects them from being destroyed by your immune system.
Causes of PNH
PNH happens because of a change (mutation) in the
PIG-A gene
PIG-A gene:
The gene that is in charge of making a protective shield of proteins on normal red blood cells. Paroxysmal nocturnal hemoglobinuria (PNH) occurs because of a change (mutation) in the PIG-A gene of a single stem cell in the bone marrow.
of a single stem cell in your bone marrow. This gene controls the creation of substance that helps certain proteins to stick to blood cells. Therefore, any blood cells created by this mutant bone marrow stem cell are abnormal.
Here are the steps that lead to PNH:
- The abnormal stem cell makes copies of or "clones" itself. This leads to a whole population of stem cells that have mutant PIG-A.
- The abnormal stem cells turn into mature red blood cells that have mutant PIG-A. These are called PNH red blood cells.
- The PNH red blood cells lack the shield of proteins that protect normal red blood cells from a part of your immune system called the complement system complement system: A group of proteins that move freely in the bloodstream. These proteins support (complement) the work of white blood cells by fighting infections. . These PNH cells are attacked and destroyed by the complement system proteins.
Many healthy people have a small number of stem cells with a PIG-A mutation mutation: Any change or alteration in a gene. A mutation may cause disease or may be a normal variation. Paroxysmal nocturnal hemoglobinuria (PNH) occurs because of a mutation in the PIG-A gene of a single stem cell in the bone marrow. . But in people with PNH, these stem cells grow fast and make lots of mature PNH red blood cells.
Some doctors believe this happens because people with PNH have bone marrow that is weaker than normal. A person's bone marrow may be weakened because they have aplastic anemia aplastic anemia: (ay-PLASS-tik uh-NEE_mee-uh) A rare and serious condition in which the bone marrow fails to make enough blood cells - red blood cells, white blood cells, and platelets. The term aplastic is a Greek word meaning not to form. Anemia is a condition that happens when red blood cell count is low. Most… or another bone marrow failure bone marrow failure: A condition that occurs when the bone marrow stops making enough healthy blood cells. The most common of these rare diseases are aplastic anemia, myelodysplastic syndromes (MDS) and paroxysmal nocturnal hemoglobinuria (PNH). Bone marrow failure can be acquired (begin any time in life) or can be… disease. Weakened bone marrow may also result from a mild bone marrow disease that was never diagnosed.
If you have had aplastic anemia, you are more likely to get PNH. There are no other known factors that increase your chances of getting PNH.