What causes aHUS?

Approximately 60-70% of aHUS cases are caused by defects in the DNA (genetic variations) or in the immune system, particularly in the body’s complement system. [1,2] For the remaining 30-40% of patients diagnosed with aHUS, the underlying cause of the disease is still not completely understood. [1-3] A family link is observed in about 20% of aHUS patients. [1,3]

While variations (also known as mutations) in genes of the complement system play a role in the development of aHUS, they are not always enough for the disease to occur. [3] It has been shown that across family members who have the same mutation(s) in the complement system, only about half will develop aHUS. [1]

These mutations then appear more as a risk factor of the disease, rather than a direct cause. [1] Often a trigger is required for aHUS to occur in those individuals that are already predisposed through a mutation. [3]

1. Loirat C, Frémeaux-Bacchi V. Atypical hemolytic uremic syndrome. Orphanet J Rare Dis. 2011;6:60.
2. Campistol JM, Arias M, Ariceta G, et al. An update for atypical haemolytic uraemic syndrome: diagnosis and treatment. A consensus document. Nefrologia. 2015;35(5):421-447.
3. Raina R, Krishnappa V, Blaha T, et al. Atypical Hemolytic-Uremic Syndrome: An Update on Pathophysiology, Diagnosis, and Treatment. Ther Apher Dial. 2019;23(1):4-21.
4. Nester CM, Barbour T, de Cordoba SR, et al. Atypical aHUS: State of the art. Mol Immunol. 2015;67(1):31-42.