Paroxysmal nocturnal hemoglobinuria (PNH)

Definition

Paroxysmal nocturnal hemoglobinuria is a rare disease in which red blood cells break down earlier than normal.

Alternative Names

Causes

Persons 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 destructive substances in the blood. The result is a break down of blood cells.

The disease can affect people of any age. It may be confused with aplastic anemia, and may turn into myelodysplastic syndrome or acute myelogenous leukemia

Risk factors, except for prior aplastic anemia, are not known.

Symptoms

• Abdominal pain
• Back pain
• Blood clots -- may form in some people
• Dark urine -- comes and goes
• Easy bruising or bleeding
• Headache
• Shortness of breath

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 may include:

• Complete blood count (CBC)
• Coombes' test
• Flow cytometry to measure certain proteins
• Ham's (acid hemolysin) test
• Urinalysis
• Serum hemoglobin and haptoglobin
• Sucrose hemolysis test

Treatment

Steroids or other drugs that suppress the immune system may help slow the break down of red blood cells. Blood transfusions may be needed. Supplemental iron and folic acid are provided. Blood thinners may also be needed to prevent clot formation.

Soliris (eculizumab) is a new drug used to treat PNH. It blocks the breakdown of red blood cells.

Bone marrow transplantation can cure this disease.

All patients with PNH should receive preventative vaccinations against certain types of bacteria to prevent infection. Ask your doctor which vaccinations are right for you.

Outlook (Prognosis)

The outcome varies. Most people survive greater 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.

Possible Complications

• Acute myelogenous leukemia
• Anemia
• Blood clots
• Death
• Iron deficiency anemia
• Myelodysplasia

When to Contact a Medical Professional

Call your health care provider if you find blood in your urine, if symptoms worsen or do not improve with treatment or if new symptoms develop.

Prevention

There is no known way to prevent this disorder.

US Food and Drug Administration. FDA Approves First-of-its-Kind Drug to Treat Rare Blood Disorder. Rockville, MD: National Press Office; March 16, 2007. Release P07-47.

Hillmen P, Young NS, Schubert J, et al. The complement inhibitor eculizumab in paroxysmal nocturnal hemoglobinuria. N Engl J Med. 2006 Sep 21;355(12):1233-43.