RPGRIP1L and Meckel syndrome, type 1: Even within the spectrum of MKS, pleiotropy exists between different types of mutations; for example, while homozygous truncating mutations of RPGRIP1L typically produce MKS it has been shown that the presence of at least one missense mutation can modify the disease severity and lead to less severe and later onset disease (Reiter and Leroux, 2017).