Germline mutations in the maternally expressed CDKN1C gene are found in 5% of sporadic BWS and ~40% of cases with a positive family history, while chromosomal rearrangements (translocations or inversions) are relatively rare (~1% of cases) [3,4,5,6,7,8,9]. The gene discussed is CDKN1C; the disease is Beckwith-Wiedemann syndrome.