Paroxysmal Nocturnal Hemoglobinuria (PNH) is a rare and serious blood disease that causes red blood cells to break apart called “hemolysis”. It happens because blood cells are missing a protein that protects them from the body’s immune system. When 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 the body. The release of hemoglobin causes most PNH symptoms. Hemolysis can put a patient at risk for serious health problems.
A rare disease, the worldwide prevalence of PNH is estimated in the range of 1–5 cases per million, regardless of ethnicity. The disease can affect people of any age. It may be associated with aplastic anemia, Myelodysplastic syndromes, or acute myelogenous leukemia
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.
Paroxysmal Nocturnal Hemoglobinuria causes occur because of a change (mutation) in the PIG-A gene of a single stem cell in the bone marrow. 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 the complement system. So they may be attacked and destroyed by the complement system proteins. Many healthy people have a small number of stem cells with mutant PIG-A. But in people with PNH, these stem cells grow fast and make lots of mature PNH red blood cells.
A person’s bone marrow may be weakened because they have Aplastic anemia or another bone marrow failure disease. Weakened bone marrow may also result from a mild bone marrow disease that was never diagnosed.