In patients with BWS, hypomethylation at IC2 occurs in 50–60%; paternal uniparental disomy (pUPD) 11p15.5 occurs in 10–20%; hypermethylation at IC1 occurs in 5–10%; and CDKN1C mutations occur in 5–10% (in 5% of sporadic cases and in 40% of familial BWS cases) [1,2,4,5,6,7,8,9]. Here, CDKN1C is linked to Beckwith-Wiedemann syndrome.