If a mum or dad in the proband is thought to hold the pathogenic variant identified from the proband, the danger for the sibs of inheriting the pathogenic variant is 50%. As a consequence of decreased penetrance, sibs who inherit the pathogenic variant may or may not establish aHUS (see https://ahu-hire38269.blognody.com/32838149/the-5-second-trick-for-ahu-hire