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

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.

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

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