Definition of Paroxysmal nocturnal hemoglobinuria (PNH)

Paroxysmal nocturnal hemoglobinuria (PNH): a rare genetic disease in which red blood cells break down too early. This breakdown leaks hemoglobin into the bloodstream that then passes into the urine (hemoglobinuria), imparting a dark color to the urine. The condition is named "nocturnal" because this hemoglobinuria most often occurs at night or in the early morning. People with this condition are also at increased risk for the development of blood clots. Symptoms include the darkened urine that comes and goes, headache, abdominal pain, back pain, shortness of breath, and easy bruising or bleeding. PNH results from an acquired mutation in the gene known as PIG-A in the red blood cells. This gene allows a substance called glycosyl-phosphatidylinositol (GPI) to help certain proteins adhere to cells. Treatment may include steroids or drugs that suppress the immune system. Blood transfusions for low red blood cell counts (anemia) may be needed. Blood thinner medications may also be needed to prevent blood clots. Soliris (eculizumab) is a drug that blocks the breakdown of red blood cells that is used in the treatment of PNH. Bone marrow transplantation can cure PNH.