GPC3 Gene

Simpson-Golabi-Behmel syndrome is a condition that affects many parts of the body and occurs primarily in males. This condition is classified as an overgrowth syndrome, which means that affected infants are considerably larger than normal at birth (macrosomia) and continue to grow and gain weight at an unusual rate. The other signs and symptoms of Simpson-Golabi-Behmel syndrome vary widely. People with mild cases often live into adulthood.

People with Simpson-Golabi-Behmel syndrome have distinctive facial features including widely spaced eyes (ocular hypertelorism), an unusually large mouth (macrostomia), a large tongue (macroglossia) that may have a deep groove or furrow down the middle, a broad nose with an upturned tip, and abnormalities affecting the roof of the mouth (the palate). The facial features are often described as "coarse" in older children and adults with this condition.

Other features of Simpson-Golabi-Behmel syndrome involve the chest and abdomen. Affected infants may be born with one or more extra nipples, an abnormal opening in the muscle covering the abdomen (diastasis recti), a soft out-pouching around the belly-button (an umbilical hernia), or a hole in the diaphragm (a diaphragmatic hernia) that allows the stomach and intestines to move into the chest and crowd the developing heart and lungs.

Simpson-Golabi-Behmel syndrome can also cause heart defects, malformed or abnormally large kidneys, an enlarged liver and spleen (hepatosplenomegaly), and skeletal abnormalities. Additionally, the syndrome can affect the development of the gastrointestinal system, urinary system, and genitalia. Some people with this condition have mild to severe intellectual disability, while others have normal intelligence.

About 10 percent of people with Simpson-Golabi-Behmel syndrome develop cancerous or noncancerous tumors in early childhood. The most common tumors are a rare form of kidney cancer called Wilms tumor and a cancerous tumor called a neuroblastoma that arises from developing nerve cells.

Wilms tumor is a form of kidney cancer that primarily develops in children. Nearly all cases of Wilms tumor are diagnosed before the age of 10, with two-thirds being found before age 5.

Wilms tumor is often first noticed because of abdominal swelling or a mass in the kidney that can be felt upon physical examination. Some affected children have abdominal pain, fever, a low number of red blood cells (anemia), blood in the urine (hematuria), or high blood pressure (hypertension). Additional signs of Wilms tumor can include loss of appetite, weight loss, nausea, vomiting, and tiredness (lethargy).

Wilms tumor can develop in one or both kidneys. About 5 to 10 percent of affected individuals develop multiple tumors in one or both kidneys. Wilms tumor may spread from the kidneys to other parts of the body (metastasize). In rare cases, Wilms tumor does not involve the kidneys and occurs instead in the genital tract, bladder, abdomen, chest, or lower back. It is unclear how Wilms tumor develops in these tissues.

With proper treatment, children with Wilms tumor have a 90 percent survival rate. However, the risk that the cancer will come back (recur) is between 15 and 50 percent, depending on traits of the original tumor. Tumors usually recur in the first 2 years following treatment and develop in the kidneys or other tissues, such as the lungs. Individuals who have had Wilms tumor may experience related health problems or late effects of their treatment in adulthood, such as decreased kidney function, heart disease, and development of additional cancers.