Beckwith-Wiedemann syndrome due to imprinting defect of 11p15

Beckwith-Wiedemann syndrome due to imprinting defect of 11p15 (BWS) is a specific molecular subtype of Beckwith-Wiedemann syndrome caused by epigenetic alterations (imprinting defects) in the 11p15.5 chromosomal region. This region contains two imprinting control centers: IC1 (regulating IGF2 and H19) and IC2 (regulating CDKN1C and KCNQ1OT1). The most common imprinting defect is loss of methylation at IC2 (also called KvDMR1 or KCNQ1OT1:TSS-DMR), accounting for approximately 50% of all BWS cases, while gain of methylation at IC1 (H19/IGF2:IG-DMR) accounts for approximately 5-10% of cases. These epigenetic changes lead to dysregulation of growth-related genes, resulting in the characteristic overgrowth phenotype. Beckwith-Wiedemann syndrome affects multiple body systems. Key clinical features include macrosomia (large body size), macroglossia (enlarged tongue), hemihyperplasia (asymmetric overgrowth of one side of the body), omphalocele or other abdominal wall defects, visceromegaly (enlarged abdominal organs), neonatal hypoglycemia, ear anomalies (anterior ear lobe creases and posterior helical pits), and renal abnormalities. A significant concern is the increased risk of embryonal tumors, particularly Wilms tumor and hepatoblastoma, especially during the first 8-10 years of life. The specific tumor risk varies by molecular subtype: IC1 gain of methylation carries a higher risk of Wilms tumor, while IC2 loss of methylation is associated with a lower overall tumor risk. Treatment is primarily supportive and symptom-based. Neonatal hypoglycemia requires prompt management to prevent neurological complications. Macroglossia may necessitate surgical tongue reduction if it interferes with feeding or breathing. Abdominal wall defects are managed surgically. Tumor surveillance protocols, including regular abdominal ultrasound screening and serum alpha-fetoprotein monitoring, are recommended throughout childhood, with the specific screening protocol tailored to the molecular subtype. Genetic counseling is important, as most cases with imprinting defects at IC2 are sporadic with low recurrence risk, while IC1 gain of methylation cases also tend to be sporadic but require careful evaluation for potential underlying genetic causes.

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