Acquired complement mediated aHUS

aHUS associated with autoantibodies against FH was first reported in 2005, and functional analyses have demonstrated disruption of complement regulation by multiple mechanisms.

There is a strong association with homozygous deletion of CFHR3 and CFHR1, which encode complement factor H-related proteins (FHR), though the mechanism is not understood: 

aHUS associated with autoantibodies against FH predominantly presents in childhood, frequently with a gastrointestinal prodrome.

Autoantibodies against FI have also been reported, but are rare and their functional relevance remains to be established.