Understanding atypical-HUS aids in rapid diagnosis and disease management
Review key details about atypical-HUS to help your patients manage this systemic, life-threatening disease.
What is atypical-HUS?
Atypical hemolytic uremic syndrome (atypical-HUS) is a rare, chronic disease that can onset at any age. It has an annual incidence* of about 0.35 to 2 per million people.1,5,32,33 Atypical-HUS is caused by dysregulation of the alternative pathway in the complement system, leading to thrombotic microangiopathy (TMA) and progressive organ damage.6,7 Patients with atypical-HUS can be at continuous risk of the life-threatening consequences of unpredictable complement-mediated TMA.5
Atypical-HUS manifests with:
Clinical characteristics of TMA4
- Microangiopathic hemolysis
- Symptoms of organ dysfunction
Absence of other underlying causes of TMA4†
- ADAMTS13 activity >5% (ruling out thrombotic thrombocytopenia purpura [TTP])
- Negative Shiga toxin-producing E. coli (STEC) test (ruling out STEC-HUS)
Learn more about how uncontrolled complement activity leads to an ongoing risk of TMA in atypical-HUS.1
*Incidence refers to the occurrence of new cases of atypical-HUS in a population over a 1-year period.31
†Where TTP and STEC-HUS have been ruled out, the TMA can be attributed to complement dysregulation. Atypical-HUS is a complement mediated TMA (CM-TMA) that has been more broadly or narrowly defined in different contexts, based on such factors as the presence and nature of a trigger and/or identification of an underlying genetic mutation.4,12,28COMPLEMENT SYSTEM & aHUS
Approximately 50% of adult patients with atypical-HUS are at risk for end-stage renal disease (ESRD) and death7‡
Chronic, uncontrolled complement activity in atypical-HUS leads to ongoing endothelial injury, organ damage, and sudden death.5,8 Familiarize yourself with the clinical complications of atypical-HUS to rapidly recognize the signs of damage in multiple organ systems and prevent further progression in your patients.
‡5-year ESRD-free survival7CLINICAL COMPLICATIONS
70% of patients (191/273) with atypical-HUS presented their first clinical manifestation while experiencing a trigger3
Triggers can amplify complement system activation and unmask underlying atypical-HUS. Some of these triggers include pregnancy or postpartum experiences, autoimmune disease, malignant hypertension, and organ transplantation.1,2 Understanding how patients may present with triggers can help to appropriately diagnose atypical-HUS.4aHUS TRIGGERS & DIAGNOSIS
Diagnosing atypical-HUS requires ruling out other causes of TMA
TMAs associated with triggers1
NOTE: The diagram is for illustrative purposes only; disease areas are not drawn to proportional scale and are not meant to reflect relative incidence.
Adapted from Azoulay E, et al. Chest. 2017;152(2):424-434.
Plasma therapy is the initial standard of care for undifferentiated TMA. However, there are limitations to plasma exchange/plasma infusion (PE/PI) in atypical-HUS. Patients remain at risk of impaired renal function and death, regardless of hematologic improvement after PE/PI. Differentiating your patients’ diagnosis between atypical-HUS or TTP is critical for rapid and appropriate disease management.4DIAGNOSING aHUS