Paroxysmal nocturnal hemoglobinuria (PNH) results from a mutation in a hematopoietic stem cell; the mutated cell then expands in the bone marrow. This mutation is usually acquired in adulthood, and the disorder is not inherited or passed down to children.
The disease causes the breakdown of circulating red cells (hemolysis), which can produce symptoms including red or darkened urine and a low red blood cell count (anemia). PNH patients can also develop aplastic anemia, which is accompanied by a decreased platelet and/or white blood count in addition to anemia. Conversely, patients with aplastic anemia sometimes develop PNH. Patients are also at increased risk of developing blood clots, which cause symptoms such as severe leg, abdominal, or chest pain, shortness of breath, jaundice, or headache.
Physicians diagnose PNH using one of two blood tests — either a Ham test or flow cytometry. Treatments for PNH patients with hemolytic anemia include transfusion, folic acid, and if appropriate, iron supplements. Low red blood cell, platelet, and white cell counts can be treated with steroids or with the same immunosuppressive drugs used to treat aplastic anemia. Blood clots are usually treated with anticoagulants, and sometimes, if severe, with tissue plasminogen activator (TPA). PNH can be cured by bone marrow transplantation; this procedure should be considered on an individual basis, based on the patient’s age and symptoms.