Conversely, homozygous inactivating mutations of GCK have been repeatedly reported (Bennett et al., 2011; Njølstad et al., 2001; Raimondo et al., 2014; Turkkahraman et al., 2008) to cause permanent neonatal diabetes mellitus (PNDM; OMIM entry #606176). This evidence concerns the gene GCK and permanent neonatal diabetes mellitus.