If a dad or mum from the proband is thought to have the pathogenic variant recognized during the proband, the risk on the sibs of inheriting the pathogenic variant is 50%. On account of reduced penetrance, sibs who inherit the pathogenic variant may or may not establish aHUS (see Penetrance). https://edgargfbun.ivasdesign.com/53908232/the-greatest-guide-to-ahu-s