PNH glossary

A

Absolute reticulocyte count (ARC)

A test that measures the amount of young red blood cells in your blood. High reticulocyte counts may be a sign of PNH, as the body is constantly making new red blood cells to replace the ones being destroyed by the immune system.

Anemia

A condition that occurs when there are not enough red blood cells to effectively carry oxygen around the body, which can cause fatigue, shortness of breath and headaches.

Aplastic anemia

A rare blood disease that is a known risk factor for PNH. Aplastic anemia occurs when a person’s bone marrow does not make enough new blood cells. Some scientists believe that aplastic anemia weakens the body’s bone marrow, which then affects its ability to produce healthy red blood cells.

B

Bilirubin test

A test that measures the total amount of bilirubin (a substance made when red blood cells break down) in your blood. A high level of bilirubin may mean that red blood cells are being destroyed, which may cause fatigue and difficulty breathing.

Blinded trial

A type of study in which participants do not know if they are taking the potential medicine or a placebo (a substance that has no therapeutic effects).

Blood transfusion

A medical procedure in which blood from a donor is given to another person through an intravenous (IV) line – a narrow tube placed within the vein of the arm.

Bone marrow

The soft fatty tissue inside certain bones that houses stem cells, some of which will ultimately become blood cells. Bone marrow provides the nutrients and environment needed for blood cells to be created. Once these cells are fully mature and ready to go to work, they leave the bone marrow and enter the bloodstream.

Bone marrow transplantation (BMT)

A treatment that replaces a person’s bone marrow stem cells with cells from a donor. BMT may be a treatment option for those with PNH who do not respond to other treatments or have a significant decrease in red and white blood cells and platelets.

C

C3

A protein located in the blood that acts as a central point of the complement system, regulating its activation.

C5

A protein located in the blood that plays an important role in inflammation and intravascular hemolysis caused by the complement system.

Chronic illness

A long-term disease or condition.

Circulatory system

A system, also referred to as the cardiovascular system, that consists of the heart, blood, vessels and glands. Its role is to circulate blood and lymph through the body.

Clone size

The percentage of red blood cells impacted by PNH. A large clone size means you have a high percentage of blood cells that can be attacked by the complement system, which may lead to more severe symptoms.

Complement system

The complement system, also referred to as the complement cascade, is an army of more than 50 different proteins that work together to get rid of dangerous cells and fight infection.

Complete blood count (CBC)

A common blood test that analyzes the amount of red and white blood cells, hemoglobin and platelets in your blood. For people with PNH, red blood cell and hemoglobin levels are typically lower than normal.

D

Dyspnea

Difficulty breathing or shortness of breath.

E

Electrocardiogram (ECG or EKG)

A test that checks how the heart is functioning by measuring its electrical activity.

Enzymes

Proteins found in all organs and cells in the body. Enzymes play an important role, as they are responsible for several chemical activities. These include breaking down food and helping to clot blood.

Etiology

The cause of a disease.

Extravascular hemolysis

Destruction of red blood cells that occurs in the liver or spleen.

F

Fatigue

Extreme tiredness or exhaustion. Fatigue is one of the most common symptoms of PNH.

Flow cytometry

The most common method of testing for PNH, this test confirms whether red blood cells are missing their protective shield. It also calculates the percentage of blood cells impacted by PNH, which is referred to as your clone size. A large clone size means you have a high percentage of blood cells that can be attacked by the complement system, which may lead to more severe symptoms.

G

Genes

Sections of our DNA that act as our body’s instruction manual. Each person has two copies of each gene, one inherited from each parent. They determine our characteristics and traits, including physical characteristics like eye and hair color. Some genes can be responsible for disease.

H

Haptoglobin assay

A test that measures the amount of haptoglobin (a protein associated with hemoglobin) in the blood. People with PNH typically have low haptoglobin levels.

Hemoglobin

The critical protein found inside red blood cells that enables other cells throughout the body to get the oxygen they need. Hemoglobin acts like drops of glue that can “stick” to oxygen and carry it from the lungs to other tissues. It can also “stick” to waste like carbon dioxide to help remove it from the body.

Hemoglobinuria

The presence of hemoglobin in the urine caused by the destruction of red blood cells.

Hemolysis

The “breaking apart” of red blood cells. It can occur when the immune system attacks these cells as though they were dangerous viruses or bacteria. When red blood cells break open, hemoglobin is released. Hemolysis causes many of the symptoms of PNH.

I

Immune system

A sophisticated defense network used to protect the body from dangers like disease and infection.

Inflammation

A response to an infection, irritation or injury. Characterized by redness, heat, swelling and pain.

Interim analysis

An analysis of the information collected from a clinical trial conducted before the trial is complete, like a “sneak peek” of the full results.

Intravascular hemolysis

The destruction of red blood cells inside a blood vessel.

Investigational New Drug

A drug that is not currently approved by the U.S. Food and Drug Administration (FDA) and is being researched in clinical trials.

L

Lactate dehydrogenase (LDH)

An enzyme found in the blood and tissues of the body, including the heart, kidneys, brain and lungs. Red blood cell destruction results in the release of LDH into the blood. People with PNH often have higher levels of LDH.

M

Myelodysplastic syndromes (MDS)

A condition that occurs when stem cells do not develop into healthy blood cells. Without enough healthy blood cells, anemia, infection and bleeding can occur. Research has found that a small number of people with PNH may also have MDS.

O

Open-label trial

A type of study in which both the researchers and the participants are aware of the treatment being given.

Organ

A structure in the body (e.g., the heart, the lungs) made up of cells and tissues.

P

Paroxysmal nocturnal hemoglobinuria (PNH)

A rare disease in which the body attacks and destroys its own red blood cells, leading to fatigue, weakness, headaches and other symptoms, including chest pain and abdominal pain.

Pathogen

A microorganism such as a bacterium or virus that causes disease.

PIG-A gene mutation

The specific change in the body’s DNA, known as a genetic mutation, that causes PNH.

Placebo-controlled trial

A clinical study in which some participants receive the potential medicine while others receive a “placebo” – a substance that looks the same but does not contain any medication. The results from these individuals are then compared.

Plasma

The fluid part of the blood responsible for transporting proteins, hormones and nutrients to cells throughout the body.

Platelets

Small, colorless cell fragments in the blood that help form clots when there’s an injury.

Progressive

A term used to describe a disease or medical condition that worsens over time.

Proteins

Large, complex molecules that play many important roles in the body and can be thought of as the “workhorses” of cells. Proteins are required for the structure, function and regulation of the body’s organs and tissues.

Q

Quality of life (QOL)

A term used to refer to a person’s health, comfort and happiness.

R

Randomized trial

A clinical study in which participants are randomly assigned to receive the potential medicine or placebo.

Red blood cells

The most common type of blood cell. Their job is to carry oxygen using an important molecule, hemoglobin, around the body.

Reticulocyte

An immature, or young, red blood cell.

S

Stem cells

Cells that can develop into many different types of cells in the body. All blood cells develop from a very small pool of specific stem cells.

T

Thrombosis

The formation of a blood clot in part of the circulatory system. Blood clots may be very serious, as they can travel to parts of the body and cause serious complications like stroke, heart attack and kidney failure.

W

White blood cells

Blood cells developed in the bone marrow that are responsible for fighting infection and disease.

A

Absolute reticulocyte count (ARC)

A test that measures the amount of young red blood cells in your blood. High reticulocyte counts may be a sign of PNH, as the body is constantly making new red blood cells to replace the ones being destroyed by the immune system.

Anemia

A condition that occurs when there are not enough red blood cells to effectively carry oxygen around the body, which can cause fatigue, shortness of breath and headaches.

Aplastic anemia

A rare blood disease that is a known risk factor for PNH. Aplastic anemia occurs when a person’s bone marrow does not make enough new blood cells. Some scientists believe that aplastic anemia weakens the body’s bone marrow, which then affects its ability to produce healthy red blood cells.

B

Bilirubin test

A test that measures the total amount of bilirubin (a substance made when red blood cells break down) in your blood. A high level of bilirubin may mean that red blood cells are being destroyed, which may cause fatigue and difficulty breathing.

Blinded trial

A type of study in which participants do not know if they are taking the potential medicine or a placebo (a substance that has no therapeutic effects).

Blood transfusion

A medical procedure in which blood from a donor is given to another person through an intravenous (IV) line – a narrow tube placed within the vein of the arm.

Bone marrow

The soft fatty tissue inside certain bones that houses stem cells, some of which will ultimately become blood cells. Bone marrow provides the nutrients and environment needed for blood cells to be created. Once these cells are fully mature and ready to go to work, they leave the bone marrow and enter the bloodstream.

Bone marrow transplantation (BMT)

A treatment that replaces a person’s bone marrow stem cells with cells from a donor. BMT may be a treatment option for those with PNH who do not respond to other treatments or have a significant decrease in red and white blood cells and platelets.

C

C3

A protein located in the blood that acts as a central point of the complement system, regulating its activation.

C5

A protein located in the blood that plays an important role in inflammation and intravascular hemolysis caused by the complement system.

Chronic illness

A long-term disease or condition.

Circulatory system

A system, also referred to as the cardiovascular system, that consists of the heart, blood, vessels and glands. Its role is to circulate blood and lymph through the body.

Clone size

The percentage of red blood cells impacted by PNH. A large clone size means you have a high percentage of blood cells that can be attacked by the complement system, which may lead to more severe symptoms.

Complement system

The complement system, also referred to as the complement cascade, is an army of more than 50 different proteins that work together to get rid of dangerous cells and fight infection.

Complete blood count (CBC)

A common blood test that analyzes the amount of red and white blood cells, hemoglobin and platelets in your blood. For people with PNH, red blood cell and hemoglobin levels are typically lower than normal.

D

Dyspnea

Difficulty breathing or shortness of breath.

E

Electrocardiogram (ECG or EKG)

A test that checks how the heart is functioning by measuring its electrical activity.

Enzymes

Proteins found in all organs and cells in the body. Enzymes play an important role, as they are responsible for several chemical activities. These include breaking down food and helping to clot blood.

Etiology

The cause of a disease.

Extravascular hemolysis

Destruction of red blood cells that occurs in the liver or spleen.

F

Fatigue

Extreme tiredness or exhaustion. Fatigue is one of the most common symptoms of PNH.

Flow cytometry

The most common method of testing for PNH, this test confirms whether red blood cells are missing their protective shield. It also calculates the percentage of blood cells impacted by PNH, which is referred to as your clone size. A large clone size means you have a high percentage of blood cells that can be attacked by the complement system, which may lead to more severe symptoms.

G

Genes

Sections of our DNA that act as our body’s instruction manual. Each person has two copies of each gene, one inherited from each parent. They determine our characteristics and traits, including physical characteristics like eye and hair color. Some genes can be responsible for disease.

H

Haptoglobin assay

A test that measures the amount of haptoglobin (a protein associated with hemoglobin) in the blood. People with PNH typically have low haptoglobin levels.

Hemoglobin

The critical protein found inside red blood cells that enables other cells throughout the body to get the oxygen they need. Hemoglobin acts like drops of glue that can “stick” to oxygen and carry it from the lungs to other tissues. It can also “stick” to waste like carbon dioxide to help remove it from the body.

Hemoglobinuria

The presence of hemoglobin in the urine caused by the destruction of red blood cells.

Hemolysis

The “breaking apart” of red blood cells. It can occur when the immune system attacks these cells as though they were dangerous viruses or bacteria. When red blood cells break open, hemoglobin is released. Hemolysis causes many of the symptoms of PNH.

I

Immune system

A sophisticated defense network used to protect the body from dangers like disease and infection.

Inflammation

A response to an infection, irritation or injury. Characterized by redness, heat, swelling and pain.

Interim analysis

An analysis of the information collected from a clinical trial conducted before the trial is complete, like a “sneak peek” of the full results.

Intravascular hemolysis

The destruction of red blood cells inside a blood vessel.

Investigational New Drug

A drug that is not currently approved by the U.S. Food and Drug Administration (FDA) and is being researched in clinical trials.

L

Lactate dehydrogenase (LDH)

An enzyme found in the blood and tissues of the body, including the heart, kidneys, brain and lungs. Red blood cell destruction results in the release of LDH into the blood. People with PNH often have higher levels of LDH.

M

Myelodysplastic syndromes (MDS)

A condition that occurs when stem cells do not develop into healthy blood cells. Without enough healthy blood cells, anemia, infection and bleeding can occur. Research has found that a small number of people with PNH may also have MDS.

O

Open-label trial

A type of study in which both the researchers and the participants are aware of the treatment being given.

Organ

A structure in the body (e.g., the heart, the lungs) made up of cells and tissues.

P

Paroxysmal nocturnal hemoglobinuria (PNH)

A rare disease in which the body attacks and destroys its own red blood cells, leading to fatigue, weakness, headaches and other symptoms, including chest pain and abdominal pain.

Pathogen

A microorganism such as a bacterium or virus that causes disease.

PIG-A gene mutation

The specific change in the body’s DNA, known as a genetic mutation, that causes PNH.

Placebo-controlled trial

A clinical study in which some participants receive the potential medicine while others receive a “placebo” – a substance that looks the same but does not contain any medication. The results from these individuals are then compared.

Plasma

The fluid part of the blood responsible for transporting proteins, hormones and nutrients to cells throughout the body.

Platelets

Small, colorless cell fragments in the blood that help form clots when there’s an injury.

Progressive

A term used to describe a disease or medical condition that worsens over time.

Proteins

Large, complex molecules that play many important roles in the body and can be thought of as the “workhorses” of cells. Proteins are required for the structure, function and regulation of the body’s organs and tissues.

Q

Quality of life (QOL)

A term used to refer to a person’s health, comfort and happiness.

R

Randomized trial

A clinical study in which participants are randomly assigned to receive the potential medicine or placebo.

Red blood cells

The most common type of blood cell. Their job is to carry oxygen using an important molecule, hemoglobin, around the body.

Reticulocyte

An immature, or young, red blood cell.

S

Stem cells

Cells that can develop into many different types of cells in the body. All blood cells develop from a very small pool of specific stem cells.

T

Thrombosis

The formation of a blood clot in part of the circulatory system. Blood clots may be very serious, as they can travel to parts of the body and cause serious complications like stroke, heart attack and kidney failure.

W

White blood cells

Blood cells developed in the bone marrow that are responsible for fighting infection and disease.