National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Atypical hemolytic uremic syndrome

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Other Names:
aHUS; Atypical HUS; HUS, atypical
Categories:
Atypical hemolytic uremic syndrome (aHUS) is a disease that causes abnormal blood clots to form in small blood vessels in the kidneys. These clots can cause serious medical problems if they restrict or block blood flow, including hemolytic anemia, thrombocytopenia, and kidney failure. It can occur at any age and is often caused by a combination of environmental and genetic factors. Genetic factors involve genes that code for proteins that help control the complement system (part of your body’s immune system). Environmental factors include certain medications (such as anticancer drugs), chronic diseases (e.g., systemic sclerosis and malignant hypertension), viral or bacterial infections, cancers, organ transplantation, and pregnancy. In about 60% of aHUS, a gene mutation may be identified. The genes associated with genetic aHUS include C3, 
CD46 (MCP), CFB, CFH, CFHR1, CFHR3, CFHR4, CFI, DGKE, and THBD. Mutations in these genes  increase the likelihood (predisposition) to developing aHUS, rather than directly causing the disease. Most cases are sporadic. In familiar cases, predisposition to aHUS is inherited in an autosomal dominant or an autosomal recessive pattern of inheritance.[1][2]


Atypical hemolytic uremic syndrome differs from a more common condition called typical hemolytic uremic syndrome. The two disorders have different causes and different signs and symptoms.[2]

Last updated: 1/23/2017

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

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Medical Terms Other Names
Learn More:
HPO ID
80%-99% of people have these symptoms
Abnormal lactate dehydrogenase level 0045040
Acute kidney injury 0001919
Hematuria
Blood in urine
0000790
Microangiopathic hemolytic anemia 0001937
Proteinuria
High urine protein levels
Protein in urine
[ more ] 		0000093
Thrombocytopenia
Low platelet count
0001873
30%-79% of people have these symptoms
Decreased level of thrombomodulin 0040229
Decreased serum complement factor B 0005416
Decreased serum complement factor I 0005356
Percent of people who have these symptoms is not available through HPO
Anuria
Absent urine output
0100519
Autosomal dominant inheritance 0000006
Autosomal recessive inheritance 0000007
Cognitive impairment
Abnormality of cognition
Cognitive abnormality
Cognitive defects
Cognitive deficits
Intellectual impairment
Mental impairment
[ more ] 		0100543
Coma 0001259
Decreased serum complement C3 0005421
Decreased serum complement factor H 0005369
Diarrhea
Watery stool
0002014
Dysphasia 0002357
Elevated serum creatinine
Elevated creatinine
High blood creatinine level
Increased creatinine
Increased serum creatinine
[ more ] 		0003259
Fever 0001945
Hemiparesis
Weakness of one side of body
0001269
Hemolytic-uremic syndrome 0005575
Hyperlipidemia
Elevated lipids in blood
0003077
Hypertension 0000822
Increased blood urea nitrogen 0003138
Purpura
Red or purple spots on the skin
0000979
Reticulocytosis
Increased immature red blood cells
Increased number of immature red blood cells
[ more ] 		0001923
Schistocytosis 0001981
Seizure 0001250
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Last updated: 7/1/2020
GeneTests lists the names of laboratories that are performing genetic testing for atypical hemolytic-uremic syndrome. To view the contact information for the clinical laboratories conducting testing click here and follow the "testing" link pertaining to each gene.

Please note:  Most of the laboratories listed through GeneTests do not accept direct contact from patients and their families; therefore, if you are interested in learning more, you will need to work with a health care provider or a genetics professional.  In the Genetic Services section of this letter we provide a list of online resources that can assist you in locating a genetics professional near you.
Last updated: 3/26/2012

FDA-Approved Treatments

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition. Learn more orphan products.

If you need medical advice, you can look for doctors or other healthcare professionals who have experience with this disease. You may find these specialists through advocacy organizations, clinical trials, or articles published in medical journals. You may also want to contact a university or tertiary medical center in your area, because these centers tend to see more complex cases and have the latest technology and treatments.

If you can’t find a specialist in your local area, try contacting national or international specialists. They may be able to refer you to someone they know through conferences or research efforts. Some specialists may be willing to consult with you or your local doctors over the phone or by email if you can't travel to them for care.

You can find more tips in our guide, How to Find a Disease Specialist. We also encourage you to explore the rest of this page to find resources that can help you find specialists.

Healthcare Resources

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Clinical Research Resources

  • ClinicalTrials.gov lists trials that are related to Atypical hemolytic uremic syndrome. Click on the link to go to ClinicalTrials.gov to read descriptions of these studies.

    Please note: Studies listed on the ClinicalTrials.gov website are listed for informational purposes only; being listed does not reflect an endorsement by GARD or the NIH. We strongly recommend that you talk with a trusted healthcare provider before choosing to participate in any clinical study.

Patient Registry

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

Social Networking Websites

  • RareConnect has an online community for patients and families with this condition so they can connect with others and share their experiences living with a rare disease. The project is a joint collaboration between EURORDIS (European Rare Disease Organisation) and NORD (National Organization for Rare Disorders).

Organizations Providing General Support

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • The Merck Manual provides information on the complement system. The Merck Manuals are a series of healthcare books for medical professionals and consumers.
  • Genetics Home Reference (GHR) contains information on Atypical hemolytic uremic syndrome. This website is maintained by the National Library of Medicine.
  • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

In-Depth Information

  • GeneReviews provides current, expert-authored, peer-reviewed, full-text articles describing the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions.
  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Atypical hemolytic uremic syndrome. Click on the link to view a sample search on this topic.

Selected Full-Text Journal Articles

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know. Submit a new question

  • My brother in law has just been diagnosed with atypical hemolytic-uremic syndrome (aHUS) and has suffered kidney failure.  We have found out his cousin also has it. One of our concerns is for my husband and our two children.  Is there a way that they can be tested to rule out aHUS? See answer


  1. Alpers CE. The Kidney. In: Kumar ed. Robbins and Cotran Pathologic Basis of Disease, Professional Edition , 8th ed. Philadelphia, PA: Saunders; 2009;
  2. Atypical hemolytic-uremic syndrome. Genetics Home Reference. 2010; http://ghr.nlm.nih.gov/condition/atypical-hemolytic-uremic-syndrome. Accessed 9/27/2010.