When you have paroxysmal nocturnal hemoglobinuria (PNH), red blood cells in your body break apart before they should. It happens because the proteins that would normally protect them from your immune system are missing. Your immune system attacks the red blood cells and breaks them down.
You can get this rare blood disease at any age. You aren’t born with it; it happens over time. Although it can be life-threatening, there are treatments to help you feel better and, in some cases, cure it.
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PNH affects everyone differently. Some people have only minor problems, but for others, it's much more severe. The biggest concern is blood clots. About 40% of people with PNH have a blood clot at some point.
PNH comes from your genes, but you don't get it from your parents and you can't pass it on to your kids.
A change in a gene causes your bone marrow to make abnormal red blood cells. This change is called a mutation.
These blood cells don't have proteins that shield them from your immune system. Your immune system attacks them, breaking them down.
Some doctors believe PNH is related to weak bone marrow. People with a certain type of anemia, called aplastic anemia, are more likely to get PNH. The reverse is also true: People with PNH are more likely to get aplastic anemia. In aplastic anemia, your bone marrow stops making new blood cells.
Not everyone with PNH has aplastic anemia.
PNH gets its name from one of its more common symptoms. About half of people with PNH pass dark or bright red blood in their urine at night or in the morning. "Paroxysmal" means "sudden," "nocturnal" means "at night," and "hemoglobinuria" means" blood in the urine."