Paroxysmal nocturnal hemoglobinuria (PNH)
Paroxysmal nocturnal hemoglobinuria is a rare disease in which red blood cells break down earlier than normal.
People with this disease have blood cells that are missing a gene called PIG-A. This gene allows a substance called glycosyl-phosphatidylinositol (GPI) to help certain proteins stick to cells.
Without PIG-A, important proteins cannot connect to the cell surface and protect the cell from substances in the blood called complement. As a result, red blood cells break down too early. The red cells leak hemoglobin into the blood, which can pass into the urine. This can happen at any time, but is more likely to occur during the night or early morning.
Risk factors, except for prior aplastic anemia, are not known.
Symptoms may include:
- Abdominal pain
- Back pain
- Blood clots, may form in some people
- Dark urine, comes and goes
- Easy bruising or bleeding
- Shortness of breath
- Weakness, fatigue
- Chest pain
- Difficulty swallowing
Exams and Tests
Red and white blood cell counts and platelet counts may be low.
Red or brown urine signals the breakdown of red blood cells and that hemoglobin is being released into the body's circulation and eventually into the urine.
Tests that may be done to diagnose this condition include:
- Complete blood count (CBC)
- Coombs test
- Flow cytometry to measure certain proteins
- Ham (acid hemolysin) test
- Serum hemoglobin and haptoglobin
- Sucrose hemolysis test
- Urine hemosiderin, urobilinogen, hemoglobin
- LDH test
- Reticulocyte count
Steroids or other medicines that suppress the immune system may help slow the breakdown of red blood cells. Blood transfusions may be needed. Supplemental iron and folic acid are provided. Blood thinners may also be needed to prevent clots from forming.
Soliris (eculizumab) is a drug used to treat PNH. It blocks the breakdown of red blood cells.
Bone marrow transplantation can cure this disease. It may also stop the risk of developing PNH in people with aplastic anemia.
All people with PNH should receive vaccinations against certain types of bacteria to prevent infection. Ask your health care provider which ones are right for you.
The outcome varies. Most people survive for more than 10 years after their diagnosis. Death can result from complications such as blood clot formation (thrombosis) or bleeding.
In rare cases, the abnormal cells may decrease over time.
Complications may include:
- Acute myelogenous leukemia
- Aplastic anemia
- Blood clots
- Hemolytic anemia
- Iron deficiency anemia
When to Contact a Medical Professional
Call your provider if you find blood in your urine, if symptoms worsen or do not improve with treatment, or if new symptoms develop.
There is no known way to prevent this disorder.
Brodsky RA. Paroxysmal nocturnal hemoglobinuria. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 31.
Michel M. Autoimmune and intravascular hemolytic anemias. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 151.