NORD gratefully acknowledges Charles J. Parker, MD, Professor of Medicine, Division of Hematology and Hematologic Malignancies, University of Utah School of Medicine, for assistance in the preparation of this report.
Paroxysmal nocturnal hemoglobinuria (PNH) is a rare disorder in which red blood cells break apart prematurely. It is an acquired hematopoietic stem cell disorder. Hematopoietic stem cells are created in the bone marrow, the spongy center of the long bones of the body. These cells grow and eventually develop into red blood cells, white blood cells and platelets. Some hematopoietic stem cells in individuals with PNH are defective and consequently produce defective blood cells. These defective red blood cells of PNH are extremely susceptible to premature destruction by a particular part of a person’s own immune system called the complement system.
The destruction of red blood cells (hemolysis) by complement leads to episodes of hemoglobin in the urine (hemoglobinuria). Hemoglobin is the red, iron-rich, oxygen-containing pigment of the blood. Individuals with hemoglobinuria may exhibit dark-colored or blood colored urine. This finding is most prominent in the morning, after the urine has concentrated overnight during sleep. However, hemolysis in individuals with PNH is a constant process, it does not occur only at night. Hemoglobin in the urine may not always be visible to the eye.
In addition to hemolysis, individuals with PNH are also susceptible to developing repeated, potentially life-threatening blood clots (thromboses). Affected individuals also have some degree of underlying bone marrow dysfunction. Severe bone marrow dysfunction results in low levels of red and white blood cells and platelets (pancytopenia). The specific symptoms of PNH vary greatly from one person to another and affected individuals usually do not exhibit all of the symptoms associated with the disorder.
Please note that some of these organizations may provide information concerning certain conditions potentially associated with this disorder.
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