Biallelic loss of function (LoF) variants in MCM3 (Mandelian inheritance in Man (MIM) *602,693), MCM5 (MIM*602,696), MCM7 (MIM*600,592), ORC1 (MIM *601,902), ORC4 (MIM *603,056), ORC6 (MIM *607,213), CDT1 (MIM *605,525), CDC45 (MIM*603,465), and CDC6 (MIM *602,627) have been identified in individuals with Meier–Gorlin syndrome (MGS). This evidence concerns the gene MCM5 and Mungan syndrome.