hemoglobinurias

Hemoglobinuria refers to the presence of free hemoglobin in the urine. This condition is usually a symptom of underlying red blood cell destruction, a process known as hemolysis. When red blood cells break down, their hemoglobin is released into the bloodstream. If the rate of hemolysis exceeds the capacity of haptoglobin, a protein that binds free hemoglobin, the excess hemoglobin is filtered by the kidneys and excreted in the urine.

The most common cause of hemoglobinuria is the intravascular hemolysis of red blood cells. This can occur in various conditions. For example, paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired clonal disorder of hematopoietic stem cells that leads to complement-mediated lysis of red blood cells. Other causes include certain infections like malaria, severe burns, mismatched blood transfusions, and some autoimmune hemolytic anemias.

The appearance of the urine in hemoglobinuria can range from pink to dark red or even black, depending on the concentration of hemoglobin. While the presence of hemoglobin in urine is the defining characteristic, it is often accompanied by symptoms related to the underlying cause of hemolysis. These can include fatigue, jaundice, abdominal pain, or fever. Diagnosis typically involves urinalysis to detect hemoglobin and blood tests to assess for anemia and evidence of hemolysis. Treatment focuses on addressing the underlying cause.