Overgrowth syndrome refers to a group of genetic disorders characterized by an unusually large birth size and excessive growth after birth. In some cases, specific body parts may be abnormally large. This group of conditions, sometimes referred to synonymously as gigantism, involve symptoms that are typically visible at birth.
Definition & Facts
There are many specific types of overgrowth syndromes each with their own unique features. The most commonly seen are Sotos syndrome and Beckwith-Wiedemann syndrome. Other overgrowth syndromes that may be diagnosed include:
- Simpson-Golabi-Behmel syndrome
- Weaver syndrome
- Proteus syndrome
- Sturge-Weber syndrome
- Macrocephaly-capillary malformation
- CLOVES syndrome
- Fragile X syndrome
Prognosis for those affected by overgrowth syndrome is generally good and the presence of the syndrome itself does not typically cause a reduction in life expectancy. The total number of diagnosed cases is unknown, but the condition occurs fairly commonly. Some overgrowth syndromes, such as Weaver syndrome and macrocephaly-capillary malformation are very rare with a limited amount of cases ever reported. By contrast, Sotos syndrome occurs in 1 out of every 15,000-20,000 births, and Beckwith-Wiedemann occurs in about 1 out of every 14,000 births.
Symptoms & Complaints
In the first six years, children often grow unusually tall, typically reaching a height in the 97th percentile. Growth commonly slows down as children age. By the time affected children reach adulthood, height is usually on the high end of the normal range. Some of the disorders may cause an increased risk of developing cancer. This usually occurs in childhood.
Affected children may experience mild to moderate intellectual disability and developmental delays. They may have difficulty reaching milestones like walking and speech, and may have hearing problems or vision problems.
Intelligence quotient (IQ) can range from less than 30 to over 100. Children may also experience issues with social development and sometimes have difficulty forming relationships with their peers.
Infants may have jaundice or have difficulty eating. The syndrome may also be accompanied disorders such as cardiovascular disease, kidney disease, or brain disease, scoliosis, seizures, neoplasia, and a higher risk of tumor development. Additional symptoms may include pain, difficulty breathing, fatigue, gastrointestinal disease, and difficulty sleeping.
In some cases, overgrowth syndromes are caused by overproduction of growth hormones by the pituitary gland prior to adolescence. One such disorder is acromegaly. When growth hormones are overproduced and bony growth plates have not closed, the long bones can grow excessively, causing individuals to reach extreme heights.
Other overgrowth syndromes are caused by chromosomal abnormalities. Affected individuals often have no family history of the disorder, suggesting that some of these syndromes may be the result of random genetic mutations or abnormalities. Less often, these syndromes are inherited.
Diagnosis & Tests
As more is learned about the specifics of each type of syndrome, physicians are better able to make accurate diagnoses. Prenatal diagnosis may be done by testing fetal cells that are collected through amniocentesis. Once a child is born, initial diagnosis is done by a thorough clinical evaluation and an assessment of the child’s physical characteristics.
Diagnosis can also be confirmed through DNA tests. Pediatricians will regularly track a child’s growth rate and compare it to established normal rates for children of the same age. This may aid in diagnosis that occurs later in life.
Treatment & Therapy
Hormone replacement therapy in the form of sex steroids (estrogen and testosterone) were used to treat overgrowth syndromes. The objective of the treatment was to fuse the ends of the bones and stop bone growth. It was found, however, that this treatment was not effective enough to warrant the potential side effects and in some cases it actually caused growth spurts.
In order to properly treat the array of medical issues that are often found in affected individuals, parents may need to consult with a team of specialists including a pediatrician, endocrinologist, geneticist, neurologist, surgeon, speech pathologist, orthopedist, ophthalmologist, physical and occupational therapists, and other health professionals.
When dealing with children who have been affected by an overgrowth syndrome, it is easy to unintentionally expect too much from them. It’s important that they are treated according to their age instead of their size. Activities and social interactions should be age-appropriate.
Treatment for overgrowth syndromes focus on managing accompanying symptoms, often through the use of various medications and occasionally, through surgeries. Regular monitoring will be needed to watch for common disorders that may be associated with the disorder. The ultimate goal of all treatments will be to make the patient comfortable and improve the quality of life.
Early intervention such as infant stimulation programs and special education may be helpful for dealing with developmental delays and intellectual and physical disabilities. Social support for both the child and the family is often necessary for coping with the condition. Depending on the specific syndrome diagnosis, clinical trials may also be available.
Prevention & Prophylaxis
Ultrasounds of the heart, abdomen, and kidneys are recommended to proactively watch of disorders. Low blood sugar is also common in affected individuals, so regular blood sugar monitoring is recommended. Children should receive a spinal examination to test for scoliosis every one to two years and blood pressure should be monitored regularly.
In order to detect potential problems and proactively intervene as necessary, children should receive eye examinations and hearing examinations, speech, and language evaluations every one to two years.
There are no known methods for preventing children from being affected by overgrowth syndromes. It is recommended that families that have had an affected child seek genetic counseling. A genetic counselor will not be able to prevent the passing of the disorder, but may be able to provide an analysis and insight regarding the likelihood of passing on overgrowth syndrome to future children.