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At a glance

A most often sporadically occurring syndrome with exomphalos, macroglossia, gigantism, and hypoglycemia caused by hyperinsulinism.

Synonyms

Wiedemann-Beckwith Syndrome; Beckwith Syndrome; Wiedemann Syndrome; Wiedemann-Beckwith-Combs Syndrome; Infantile Gigantism; EMG Syndrome; Exomphalos-Macroglossia-Gigantism Syndrome; Familial Macroglossia-Omphalocele Syndrome; Macroglossia-Omphalocele-Visceromegaly Syndrome.

History

First described in three autopsy cases by the American pediatric pathologist John Bruce Beckwith in 1963. The German pediatrician Hans-Rudolf Wiedemann reported on two further (living) patients 1 year later and added the findings of hypoglycemia and postnatal gigantism to the picture.

Incidence

Has been estimated to be in the range of 1: 10,500 to 13,700, although some experts consider the true incidence to be higher as many cases may go undiagnosed due to a mild phenotype. Males and females are affected equally.

Genetic inheritance

While approximately 15% of all cases are inherited in an autosomal dominant mode with incomplete penetrance and variable expressivity, the vast majority of cases are sporadic. BWS is caused by mutations in the ICR1 (H19-IGF2-imprinting control region) gene (in 25% of patients, paternal uniparental disomy in 80% of those), or the H19 gene, or the KCNQ1OT1 (Potassium Channel, Voltage-Gated, KQT-Like Subfamily, Member 1, overlapping transcript 1) gene (in about 50%) or rarely (in 5%), by mutations in the CDKN1C (Cyclin-dependent kinase inhibitor 1C) gene, all located on chromosome 11p5. In the remaining 20% of BWS patients, the molecular basis remains undetermined. There is now a recognized association between assisted reproduction technology and BWS, but the absolute risk of BWS in an individual conceived by assisted reproduction technology appears to be very low (no more than 1 in 1,000).

Pathophysiology

The 11p15 chromosome region contains growth-promoting (IGF-2 and KCNQ1OT1) and tumor-suppression genes (H19 and CDKN1C). The mutations of these genes lead to somatic overgrowth and predisposition to tumors. Altered placental endocrine physiology (placental mesenchymal dysplasia) may play a role in producing many of the features already found during the neonatal period. Omphalocele, anomalies of intestinal rotation and fixation, and diaphragmatic eventration may be secondary to early visceromegaly.

Diagnosis

During pregnancy, polyhydramnios, enlargement of the placenta (up to twice the normal size) with increased length of the umbilical cord are characteristic. The birth weight for boys and girls is around the 95th and 75th percentile, respectively. Growth velocity is increased in the first 4 to 6 years of life (postnatal growth >90th percentile) and associated with advanced bone age, but normalizes thereafter. Severe hypoglycemia is present in approximately 30 to 60% of newborns, with the highest incidence found in the first 3 days of life. Macroglossia and omphalocele or umbilical defects, ear lobe grooves, and circular depression on the posterior rim of helix are other features. Final confirmation of the diagnosis requires molecular/cytogenetic testing.

Beckwith-Wiedemann Syndrome: Pronounced ...

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