If a dad or mum in the proband is thought to provide the pathogenic variant recognized in the proband, the danger into the sibs of inheriting the pathogenic variant is 50%. As a consequence of reduced penetrance, sibs who inherit the pathogenic variant may or may not develop aHUS (see https://ahu-hire19641.blog-kids.com/32060178/the-fact-about-air-handling-units-ahus-that-no-one-is-suggesting