There are many characteristics that are associated with BWS, but most children who are affected have only a few of them. The diagnosis should be made when at least two of the major and one of the minor criteria are noted. The most commonly found are described below:
ABDOMINAL WALL DEFECTS: These vary in severity. The worst problem is an omphalocele which allows intestines and possibly other organs to protrude externally into a covering membrane (although, typically, these are “bowel only” omphaloceles). Less serious is an umbilical hernia (seen in this case). Alternatively, lax abdominal musculature can lead to a “prune belly” appearance.
MACROGLOSSIA: An enlarged tongue, which may cause breathing, feeding and speaking difficulties (very dramatic in this fetus).
MACROSOMIA: Height and weight over the 90th percentile (one may reason that this fetus is macrosomic because at 34 weeks gestation, the abdominal circumference is already greater than that of a 40 week fetus).
VISCEROMEGALY: Enlarged abdominal organs, usually the kidneys, but also liver, spleen, adrenals and pancreas (the kidneys and pancreas are seen to be enlarged in this fetus).
POLYHYDRAMNIOS AND THICKENED PLACENTA: Polyhydramnios is often seen with macrosomia, but may also have other origins in BWS (it is present in this case, but not easily visible on the sonograms selected to illustrate the syndrome). The placenta commonly weighs twice normal in size.
OTHER IMPORTANT FEATURES (USUALLY SEEN POSTNATALLY):
HYPOGLYCEMIA: This occurs in approximately 40% of BWS children shortly after birth. Brain damage and other complications can result if it is not diagnosed and treated. Untreated hypoglycemia may account for some of the sporadic mental retardation encountered with the syndrome.
WILMS TUMORS, HEPATOBLASTOMA, ADRENAL TUMORS: Around 7.5% of BWS children will develop Wilms tumor. Because of the aggressiveness of these tumors, abdominal ultrasound scans should take place at relatively short intervals up to the age of 7 or 8 years. The susceptibility to these tumors diminishes and is not usually a problem after the age of 8. Children with one side of the body bigger than the other (hemihypertrophy) or enlarged kidneys appear to be more susceptible to Wilms tumor than other BWS children. Abdominal sonograms performed to assess for interval development of Wilms tumor should also search for other abdominal neoplasia (especially those of the liver and adrenal).
HOW IS BWS FOUND IN FETUSES?
Many cases of BWS come to light because maternal serum alpha-fetoprotein testing demonstrates an elevated level. In utero sonography then typically detects the omphalocele in early pregnancy. During the evaluation for the detected omphalocele, a karyotype is performed but will be normal, as is the fetal echocardiogram (although there are occasional cardiac defects). Unfortunately, macrosomia, macroglossia, visceromegaly, polyhydramnios and placentomegaly are later findings. Thus, the patient typically is in the third trimester before the diagnosis becomes evident. Counseling of patients whose fetus demonstrates an omphalocele in early pregnancy should contain a caution about BWS.
MODE OF INHERETANCE: The mode of inheritance in BWS is complex. The syndrome is usually sporadic, but may be inherited.
A locus on chromosome 11 is strongly implicated.
FREQUENCY: The frequency is estimated at 1 in 15,000 live births. Incidence is higher in fetuses conceived through in vitro fertilization.
RACE: No race predilection exists.
SEX PREDILECTION: No sex predilection exists.