Glossary
Anemia
A condition in which your body does not have enough hemoglobin (the oxygen-carrying component of your blood) inside the red blood cells (RBCs). Alternatively, the number of RBCs may be reduced. This may cause tiredness and other symptoms and contribute to fatigue.
Aplastic anemia
A condition where the bone marrow does not produce enough new red blood cells and possibly all other blood cells. The term “aplastic” means that the bone marrow is unable to produce new blood cells properly. Patients with aplastic anemia have lower counts of all three blood cell types: red blood cells, white blood cells, and platelets. PNH is often found in combination with aplastic anemia.
Blood clot
When platelets and fibrinogen, a protein that is the essential component of the coagulation system within the blood, bind together, they form a blood clot (also called “thrombus”). These clots can block blood flow in the veins and arteries, depending on their size and location (see Thrombosis), and can cause serious problems in patients with PNH.
Bone marrow
Soft tissue inside your large bones. Bone marrow contains stem cells, which form red blood cells, white blood cells, and platelets through a process called hematopoiesis.
Complement
Part of your body’s defense system that destroys foreign organisms (e.g., bacteria) as well as whole cells (self or foreign). In PNH, complement is responsible for the destruction of red blood cells that lack specific protective proteins.
Complete blood count (CBC)
Tests performed on a small amount of your blood that can provide information about the amount of each type of blood cell.
Glycosyl-phosphatidylinositol (GPI)
An important type of anchor that attaches proteins to the cell surface. PNH red blood cells lack GPI-anchored proteins. Without these GPI anchors, certain proteins are missing from the surface of cells, leaving the cells vulnerable to destruction by the body’s complement system (see Complement).
Hematocrit
The amount of your blood volume that is occupied with red blood cells.
Hemoglobin
The brownish-red substance in red blood cells that carries oxygen throughout your body.
Hemoglobinuria
Hemoglobin in the urine. Hemoglobinuria is the technical term for the “cola-colored” or dark urine seen in approximately 25% of patients with PNH at diagnosis. When the red blood cells that are missing the protective protein are destroyed, as they are in PNH, hemoglobin is released from the red blood cells. If hemoglobin is not all processed by the body’s systems, it is sent out as waste and gives the urine a characteristic cola-brown color.
Hemolysis
The destruction of red blood cells. Destruction of red blood cells is the main cause of major health problems associated with PNH.
Lactate dehydrogenase (LDH)
An enzyme that is found in many organs in the body, and is especially abundant in red blood cells. LDH is a key marker of hemolysis, the underlying cause of the signs and symptoms associated with PNH.
Myelodysplastic syndromes (MDS)
A large and heterogenous group of blood disorders in which there are problems with the proper production of blood cells within the bone marrow. MDS typically occur in elderly people and have a certain risk of converting into so-called “acute leukemia.” For this reason, MDS sometimes are also called “preleukemic states.” PNH is sometimes, but not often, found in combination with MDS (i.e., about 2% of all PNH patients also suffer from MDS).
Paroxysmal nocturnal hemoglobinuria (PNH)
A disease characterized by chronic red blood cell destruction, often resulting in serious health problems. Signs and symptoms can include stomach pain, difficulty swallowing, anemia, shortness of breath, tiredness (fatigue), and life-threatening complications such as blood clots, kidney failure, and damage to vital organs.
Platelets (thrombocytes)
Cells in your blood that are essential components in the clotting process. In concert with certain proteins, platelets help stop bleeding when you’ve cut yourself and block blood flow inside blood vessels. In certain disease states, such as PNH, they may stick together and form a potentially harmful clot inside blood vessels.
PNH clone
A group of cells in your body that are affected by the genetic defect that causes PNH. The extent to which your blood cells are affected by PNH is often described in terms of one’s clone size.
Red blood cells (RBCs)
Red blood cells are constantly traveling through your body delivering oxygen and removing waste (carbon dioxide). PNH red blood cells are continually attacked and destroyed by part of the body’s defense system known as complement because they are missing important protective proteins.
Thromboembolism
The blocking of a blood vessel by a particle that has broken away from a blood clot at its site of formation.
Thrombosis
The formation or development of a blood clot that often blocks blood from flowing through a vessel (vein or artery). Blood clots can cause life-threatening complications for anyone, including patients with PNH. Hemolysis significantly increases the risk of blood clots in patients suffering from PNH (see Blood clot).