Overgrowth Syndromes

Overgrowth syndromes are a rare group of genetic disorders that cause excessive growth before and after birth.

This excessive growth can affect almost any part of the baby’s body, including bones, muscles, blood vessels, organs, skin and fat. It may be “localized,” meaning it affects only a certain area of the body, or “generalized,” meaning the child’s whole body is affected.

Overgrowth syndromes can cause serious physical deformities and significant, in some cases life-threatening health issues.

The overgrowth is typically present at birth and may continue throughout childhood.

How will overgrowth affect my baby?

Babies with these genetic disorders are often larger than average at birth.

The newborn may be significantly heavier (macrosomia) and longer than normal, and may have an abnormally large head (macrocephaly).

While each overgrowth syndrome has its own unique pattern of signs and symptoms, common complications associated with these disorders include:

• Intellectual disabilities
• Congenital defects (such as heart or kidney defects)
• Increased risk of developing certain cancers during childhood

Cause

Overgrowth syndromes are caused by gene mutations or abnormalities. The exact genetic cause is sometimes unknown.

In some children the overgrowth may be the result of an inherited gene change, while other children have a new gene change with no family history.

Examples of Overgrowth Syndromes

Overgrowth syndromes are an extremely diverse group of conditions, each with its own distinctive group of signs and symptoms. However, some symptoms are overlapping – meaning they can be found in more than one syndrome – which can complicate diagnosis.

Some examples of overgrowth syndromes and a few of their characteristics include:

• Beckwith-Wiedemann syndrome – an abnormally large body (macrosomia), parts of the body larger on one side (hemihyperplasia), abdominal defects such as omphalocele (the intestines and other organs protrude out through the navel), enlarged abdominal organs, kidney abnormalities, an abnormally large tongue (macroglossia), cardiac anomalies, ear creases/pits
• Sotos syndrome – a large, long head, distinctive facial features including a protruding forehead and  pointed chin, brain abnormalities and cognitive impairment, large hands and feet, congenital heart disease, enlarged abdominal organs, scoliosis
• Simpson-Golabi-Behmel syndrome – an abnormally large body and head, square-shaped face, unusually large mouth and tongue with a deep groove in the lower lip and tongue, short hands, fingers, and toes, heart defects, extra nipples, congenital diaphragmatic hernia, agenesis of the corpus callosum, intellectual disability, enlarged kidneys
• Weaver syndrome – tall stature, joint deformities that restrict movement, scoliosis, large hands and feet, a broad forehead, widely spaced eyes, lower jaw set further back than upper jaw, bent fingers, low muscle tone (hypotonia)
• Proteus syndrome – symptoms appear within the first years of life and progressively worsen, including overgrowth of bones, blood vessels, fat and skin, with asymmetric leg bones causing difficulty walking, intellectual disability, seizures, vision loss, life-threatening blood clots
• PIK3CA-related overgrowth spectrum (PROS) – associated with multiple conditions in which overgrowth of different tissue types occur across the body, including:
  • Megalencephaly-capillary malformation syndrome (MCAP) – large brain with enlargement of the capillaries that causes malformations
  • Hemimegalencephaly – overgrowth of only one hemisphere of the brain that may cause intellectual disability and seizures
  • Fibroadipose hyperplasia – patchy overgrowth of a limb or part of the body due to fatty, fibrous and/or blood vessel overgrowth
  • CLOVES syndrome – fatty overgrowth in the trunk, overgrowth of the arms, hands, legs or feet, spine abnormalities including curvature of the spine, deformities of the blood vessels, birthmarks
  • Klippel-Trènaunay syndrome – overgrowth of blood vessels causing red birthmark (known as a port-wine stain) and varicose veins, overgrowth of bones and soft tissue, often in one leg, abnormalities of the lymphatic system (part of the immune system), fused or extra toes or fingers, internal bleeding
• Parkes-Weber syndrome – limb overgrowth, capillary abnormalities causing port-wine stains (red/purple skin), large veins, arteriovenous malformations, heart failure
• Sturge-Weber syndrome – facial (port-wine) birthmark caused by an overabundance of capillaries beneath the skin, neurological abnormalities, seizures, muscle weakness or paralysis on one side of the body, headaches, eye/vision abnormalities, endocrine disorders
• Madelung’s disease – large accumulation of fatty tumors around the neck, shoulders, upper arms and trunk, impaired nerve function in the arms and legs, diabetes, hypertension, liver disease
• Pallister-Killian syndrome – extremely weak muscle tone that can affect breathing, feeding and walking, severe intellectual disability, limited speech, distinctive facial features and large tongue, sparse hair, areas of unusual skin coloring, congenital diaphragmatic hernia
• Perlmansyndrome – enlarged kidneys, increased risk for kidney cancer (Wilms tumor), neurodevelopmental delay, high neonatal mortality

Diagnosis

During Pregnancy

An overgrowth syndrome may be suspected following a routine prenatal ultrasound or visit that detects the fetus is unusually large for their gestational age (LGA).

If the two common causes of large for gestational age are ruled out – incorrect pregnancy dating and maternal diabetes – an overgrowth syndrome may be considered, especially if additional fetal anomalies are detected. Imaging may also show polyhydramnios (too much amniotic fluid), a pregnancy complication common with overgrowth syndromes.

A diagnosis of overgrowth syndrome typically isn’t confirmed until after birth. However, detection or suspicion of these genetic disorders during pregnancy enables your family and your healthcare team to prepare for any special care or treatment your baby may need at birth.

A geneticist and genetic counselor experienced in the diagnosis and treatment of these rare disorders should be involved in the diagnostic process.

At Birth

An overgrowth syndrome may be diagnosed or confirmed after birth based on:

• Physical exams and imaging to evaluate the overgrowth and the baby’s health (imaging may include ultrasound, MRI, x-rays, and/or CT scans)
• The symptoms and characteristics associated with each overgrowth syndrome
• Genetic testing of a blood or tissue sample (biopsy)

Accurate diagnosis is important for appropriate treatment planning, including monitoring for cancer throughout childhood as needed, and for genetic counseling.

In some cases, where the baby’s signs and symptoms are common across more than one overgrowth syndrome, a specific diagnosis can be more challenging, particularly if there is no genetic test available.

Specialized Evaluation and Prenatal Care

If an overgrowth syndrome is diagnosed or suspected during pregnancy, you may be referred to a fetal center for further evaluation.

At Texas Children’s Fetal Center, we arrange for you to visit as quickly as possible for a comprehensive assessment by a team of specialists experienced in the diagnosis and treatment of these rare genetic disorders. Your team may include maternal-fetal medicine physicians (OB/GYNs specializing in high-risk pregnancies), fetal imaging experts, neonatologists, genetic counselors, and geneticists from Texas Children’s Genetics Clinic, the largest genetics clinic in the country.

Additional testing will be performed using state-of-the-art imaging technologies and techniques that provide detailed views of your baby’s condition, for the most accurate diagnosis. Testing may include:

• High-resolution anatomy ultrasound to evaluate the baby’s condition and look for abnormalities
• Ultra-fast MRI for a more detailed view of fetal anatomy
• Fetal echocardiogram to evaluate the baby’s heart
• Amniocentesis to help diagnose genetic conditions associated with overgrowth

Our specialists will then meet with you about the results, discuss delivery and treatment planning, and answer any questions your family has, to help you make the most informed decisions regarding your baby’s care and treatment.

Mother and baby will be closely monitored throughout pregnancy with frequent ultrasounds to assess the progression of the overgrowth and watch for signs of complications.

Delivery

A cesarean delivery may be necessary due to the size of the baby, to prevent injury to the newborn or the mother.

We recommend delivery at a hospital with the expertise and resources required to care for pregnancies involving overgrowth syndromes, including the highest level neonatal intensive care unit (NICU). 

Delivery and postnatal care should be carefully planned and coordinated by a team of maternal-fetal medicine physicians, neonatologists, and pediatric specialists. Our Fetal Center team works closely with experts from Texas Children’s Hospital, consistently ranked one of the best children’s hospitals in the nation by U.S. News & World Report. For our patients, that means seamless access to the critical care services and pediatric specialists your baby may need after birth, with no transfers required.

Treatment After Birth

There is no cure for overgrowth syndromes. Treatment depends on each baby’s unique symptoms and condition. 

In general, postnatal care may include:

• Physical exams, imaging and genetic testing to confirm the diagnosis
• Medical or surgical treatment to relieve symptoms
• Close monitoring of the continued overgrowth
• Regular tumor screening, as needed

Postnatal Care Team

Children with overgrowth syndromes typically require coordinated care across multiple specialists and healthcare professionals.

While the healthcare needs vary for each child, in general a postnatal care team may include:

• Neonatologist
• Primary care pediatrician
• Pediatric surgeon
• Geneticist/genetic counselor
• Pediatric neurologist
• Developmental pediatrician
• Pediatric orthopedic surgeon
• Pediatric oncologist
• Social worker
• Pediatric psychologist

Why Texas Children’s Fetal Center?

• A single location for expert maternal, fetal, and pediatric care. At Texas Children’s Hospital, mother and baby receive the specialized care required for the diagnosis and treatment of an overgrowth syndrome all in one location, for highly coordinated care and treatment planning, including immediate access to our level IV NICU if needed.
• A skilled, experienced team with proven outcomes. We have a dedicated team of maternal-fetal medicine specialists, fetal imaging experts, geneticists, neonatologists, and others who work in concert to care for you and your baby every step of the way, using proven protocols we’ve developed over the years. With their combined expertise and unified approach, this team offers the best possible care for pregnancies involving overgrowth syndromes.
• We care for your child at every stage of life. Our comprehensive approach starts with your first prenatal visit and continues through delivery, postnatal care, and childhood, thanks to one of the nation’s leading teams of fetal and pediatric specialists for the care and treatment of rare genetic disorders.

Videos

• Texas Children’s Fetal Center: Our care began before he/she was born

Additional Resources

• 6 things to consider when choosing a fetal center