Paroxysmal Nocturnal Hemoglobinuria (PNH)

In paroxysmal nocturnal hemoglobinuria (PNH), the bone marrow—the soft, spongy tissue that acts as the blood manufacturing system for the entire body—produces defective red blood cells. The body's natural defense system then destroys these defective red blood cells in a process known as hemolysis.

Healthy red blood cells help deliver oxygen and remove waste from the body. When red blood cells are damaged or destroyed, the result is acquired anemia, abnormal clotting (thrombosis), impaired bone marrow function, and a 3–5% chance of developing leukemia.

No one knows what causes this disorder. 


Because of the wide range of symptoms for PNH, patients often go months or years before receiving the correct diagnosis. Symptoms may include:

  • Severe abdominal pain 
  • Severe headaches
  • Back pain
  • Fatigue and excessive weakness
  • Recurring infections
  • Bright red blood in the urine (hemoglobinuria) in the morning, triggered by infections, alcohol, exercise, stress, or reaction to medication
  • Dark tea-colored urine
  • Blood clots (thrombosis) in the veins or arteries


To confirm the diagnosis, a physician may order the following blood tests:

  • A complete blood count to check the numbers of red and white blood cells
  • Sucrose hemolysis (sugar water), a blood test to detect fragile red blood cells by testing their ability to withstand swelling in a low-salt solution 
  • The Ham test, a blood test to find out whether red blood cells become more fragile when they are placed in mild acid.
  • Flow cytometry, a technique for identifying and sorting cells and their components (as DNA) by staining them with a fluorescent dye and illuminating them with a laser beam

Risk Factors

PNH affects only about 8,000 to 10,000 people in North America and Western Europe. It is an acquired disease and is not genetically inherited from a family member. Some patients with aplastic anemia, a disease that affects the bone marrow and causes low blood counts, can develop PNH.

  • Both men and women can get PNH
  • PNH occurs across all races
  • PNH can occur at any age; the average age at diagnosis is in the early 30s


A genetic cause for PNH has recently been identified and will hopefully lead to more effective treatments.

Currently, those with few or no symptoms are given folic acid and iron supplementation to increase their red blood cell production.

Anemic patients whose red blood cells are rapidly being killed off are given prednisone to slow the rate of destruction.

Those with acute thrombosis (clotting) may receive thrombolytic therapy (streptokinase, urokinase, or tissue plasminogen activator) and anticoagulation drugs, along with aspirin and ibuprofen to help prevent blood clots.

PNH patients may also be treated with antithymocyte globulin (ATG) or red cell or platelet transfusions.

The drug eculizumab (Soliris) is also used to treat the disease.

Bone Marrow Transplant

Allogeneic (from a donor) bone marrow transplantation (BMT) may be prescribed as a curative therapy for select patients with PNH. A transplant replaces all of the bone marrow stem cells with those of a healthy sibling.

Learn More About Bone Marrow/Stem Cell Transplantation