Get ready for some PNH science!

This is what happens in your blood when you have PNH

Normal red blood cell

Step 1

Normal red blood cells have a protein layer, called CD59, that protects them from the immune system.

PNH red blood cell

Step 2

PNH red blood cells lack the CD59 layer due to a mutation in the PIG-A gene. This leaves them open to being attacked by the complement system (part of the immune system).

The complement system attacks PNH red blood cells through a process called hemolysis.

Step 3

"Hemo" = refers to blood
"Lysis" = means to burst

There are two types of hemolysis that can happen:

• Intravascular = hemolysis inside the circulatory system (made up of blood vessels that carry blood to and away from the heart)
• Extravascular = hemolysis outside the circulatory system (e.g., inside the spleen)

When PNH red blood cells are destroyed, the hemoglobin that they contain is released and removed from the body.

Step 4

This results in lower levels of hemoglobin, known as anemia, triggering many PNH symptoms, such as fatigue and shortness of breath.

When hemolysis happens quickly, and more red blood cells are being destroyed than made, it can cause a hemolytic crisis. When this happens, hemoglobin levels drop quickly. This can sometimes result in the need for a blood transfusion, and can also cause a flare of PNH symptoms.

What causes a hemolytic crisis?

• Lack of or defects in certain proteins that are inside red blood cells
• Autoimmune diseases
• Bacterial or viral infections
• Side effects to certain medications
• Reactions to blood transfusions