Paroxysmal Nocturnal Hemoglobinuria (PNH)

PNH is a rare and serious blood disease that causes red blood cells to break apart. Doctors call this breaking apart "hemolysis". It happens because your blood cells are missing a protein that protects them from your body's immune system.

When your red blood cells break apart, the hemoglobin inside them is released. Hemoglobin is the red part of red blood cells. Its job is to carry oxygen around your body. The release of hemoglobin causes most PNH symptoms.

The disease can affect people of any age. It may lead to aplastic anemia, myelodysplastic syndromes, or acute myelogenous leukemia.

Where does the name come from?

Here's where the name "paroxysmal nocturnal hemoglobinuria" comes from:

  • Paroxysmal - means "sudden and irregular"
  • Nocturnal - means "at night"
  • Hemoglobinuria - means "hemoglobin in urine"; hemoglobin is the red part of red blood cells - it makes your urine look dark

So, "paroxysmal nocturnal hemoglobinuria" means sudden, irregular episodes of passing dark colored urine, especially at night or in the early morning. It is important to note that many people with PNH do not have dark urine.

What is the complement system?

The complement system is a group of proteins in the blood. They help support (complement) the work of white blood cells by fighting infections.

These proteins are always active at a very low level. But when bacteria, viruses, and other foreign or abnormal cells get into your body, these proteins become more active. They work together to attack and destroy the abnormal cells in your body.

Normal red blood cells have a shield of proteins. This shield protects the cells from being attacked by the complement system. The gene in charge of making this protective shield is called PIG-A.