Beckwith-Wiedemann syndrome (BWS) is a growth disorder that can affect several parts of the body. Babies and children are larger than normal usually until age 8, when growth slows down, resulting in an average height in adults. Symptoms may include one side or area of the body growing more than the other side (asymmetric growth or hemihyperplasia), omphalocele or other abdominal wall defect at birth, low blood sugar (hypoglycemia) in infancy, an abnormally large tongue (macroglossia), abnormally large abdominal organs, creases or pits in the skin near the ears, and kidney abnormalities. Affected children have an increased risk to develop tumors, particularly a rare form of kidney cancer called Wilms tumor, a cancer of muscle tissue called rhabdomyosarcoma, and a form of liver cancer called hepatoblastoma. Some people only have one symptom while others may have many of the symptoms. The cause of BWS is complex and is different for different people, but involves genes that control body growth. The genes, including the CDKN1C, H19, IGF2, and KCNQ1OT1 genes, are located on chromosome 11. In most cases BWS is caused by problems with the genomic imprinting of these genes. Genomic imprinting refers to having some genes that are active (expressed) only when inherited from the father and others that are active only when inherited from the mother. Less commonly, changess in the CDKN1C gene or larger changes to chromosome 11, such as a translocation, deletion, or duplication, may cause BWS. Diagnosis of BWS is based on symptoms with the support of genetic testing. At present however, there is no clearly accepted diagnostic criteria as doctors are trying to understand the full spectrum of possible symptoms.