If a mother or father on the proband is understood to possess the pathogenic variant discovered within 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 acquire aHUS (see https://andresnfvj.ampblogs.com/the-definitive-guide-to-air-handling-unit-ahu-hire-68937174