It’s a rare blood disease that stems from your genes. If you have it, your immune system attacks red blood cells in your body and breaks them down. They lack certain proteins that protect them.
You can get paroxysmal nocturnal hemoglobinuria (PNH) at any age. You aren’t born with it. Although it can be life-threatening, treatments can help you feel better and control some of its complications.
The condition affects everyone differently. Some people have only minor problems. For others, it's much more severe. The biggest risk is blood clots. About 40% of people with PNH have one at some point.
PNH is genetic. But you don't get it from your parents, and you can't pass it on to your kids.
A change in a gene, called a mutation, causes your body to make abnormal red blood cells. These cells don’t have proteins that shield them from your immune system. So your body breaks them down. Scientists call this process “hemolysis.”
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, though not everyone does. In this condition, your bone marrow stops making new blood cells.
The condition gets its name from one of its symptoms: dark or bright red blood in your urine at night or in the morning. "Paroxysmal" means "sudden," "nocturnal" means "at night," and "hemoglobinuria" means "blood in the urine." It happens in over 60% of people with PNH.