If a dad or mum in the proband is understood to have the pathogenic variant recognized from the proband, the chance to 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 produce aHUS (see https://jasperqngxn.mybjjblog.com/how-air-handling-unit-ahu-hire-can-save-you-time-stress-and-money-45185796