Atypical hemolytic uremic syndrome 4 (aHUS 4) is a rare genetic disease in which red blood cells are abnormally destroyed, leading to a decreased red blood cell count (anemia) and destruction of the platelets (thrombocytopenia). Platelets are found circulating in the blood and are involved in clot formation to stop bleeding. aHUS 4 is a chronic and often progressive condition. This particular type of aHUS is caused by a defect in complement factor B, which is a protein involved in the complement system. The complement system is a part of the immune system that helps to get rid of things that may be harmful to the body.
Early symptoms of aHUS 4 include malaise, tiredness, lethargy, and irritability. Later, individuals usually develop swelling, blood in the urine, protein in the urine, and a reduced amount of albumin in the blood. Albumin is a major protein in blood that helps to regulate blood pressure and transport proteins and other substances. The debris from destroyed red blood cells in aHUS 4 can clog or damage the tiny blood vessels in the kidney, which is the organ that filters blood and produces urine. Kidney failure may occur and is a feared complication of this condition.
aHUS 4 is often diagnosed based on family history, genetic testing, and signs of a low red blood cell count (anemia), a low platelet count (thrombocytopenia), and kidney damage. Treatment may include IV fluid and nutrient replacement, blood transfusions, and medication to help maintain blood pressure. If the kidneys stop working, then dialysis may be needed in order to filter the blood. If you or a loved one has been diagnosed with aHUS 4, talk to your doctor about the most current treatment options. In addition, a genetic counselor can help discuss inheritance and risks to other family members.