What is hemihypertrophy?
Hemihypertrophy, also referred to as hemihyperplasia, is a condition in which one side of the body or a part of one side of the body is larger than the other.
Hemihypertrophy is related to several congenital syndromes including Beckwith-Wiedemann syndrome and Russell-Silver syndrome. These syndromes are both congenital, which means they are present at birth, and they are genetic, meaning they are passed down from the parents. If a child has hemihypertrophy and it is not related to a syndrome such as these, it is called "isolated hemihypertrophy."
Hemihypertrophy is an overgrowth disorder, and the asymmetry, or unevenness of the body, can range from mild to severe.
Diagnosing hemihypertrophy as soon as possible is important because it is associated with an increased risk for tumors such as Wilms tumor and hepatoblastoma, a type of solid tumor.
Hemihypertrophy is different from many genetic diseases because the genes that cause the disorder can differ from person to person. Genes are made up of deoxyribonucleic acid (DNA), which are made up of chromosomes. Genes form a kind of blueprint for the body and tell it how to form and function. When a gene is mutated or missing, it affects how the body grows.
Hemihypertrophy in children
Hemihypertrophy can be inherited from a child's parents, although it is not always clear which gene causes the disorder. A mutation on chromosome 11 is often associated with hemihypertrophy when linked to Beckwith-Wiedemann syndrome.
What are the signs and symptoms of hemihypertrophy?
The most noticeable sign of hemihypertrophy is that one side of the body is larger than the other. Many times, a leg or an arm will be longer or larger in circumference than the other. However, it isn't always obvious. Sometimes hemihypertrophy is hard to notice unless your child is laying down flat – this is called the "bed test" In other instances, you may notice a difference in their posture or gait (how they walk).
What tests are used to diagnose hemihypertrophy?
Hemihypertrophy is often associated with overgrowth syndromes such as Beckwith-Wiedemann syndrome, proteus syndrome, neurofibromatosis Type 1 and mosaic trisomy 8. It is also associated with vascular malformations such as Klippel-Trenaunay syndrome and megalencephaly-cutis marmorata telangiectatica congenital (CMTC).
At Children's Hospital Colorado, we first do genetic testing to identify if the condition is associated with another disease. For the test, we will need to get a DNA sample by swabbing the inside of the cheek or by taking a blood sample. Further testing and treatment will differ depending on if there is a second disease found during the genetic test.
Screening for tumors related to hemihypertrophy
Due to the increased risk of tumors, we also recommend screening for all children with hemihypertrophy. For tumor screening, we use imaging tests such as ultrasounds and magnetic resonance imaging (MRI).
If the genetic testing reveals no other associated syndromes, but your child's doctor still observes asymmetrical growth, they will most likely be diagnosed with isolated hemihypertrophy.
How is hemihypertrophy treated?
Although children with hemihypertrophy can develop problems in their bones and joints, most of the treatment focuses on combating the increased risk of tumors.
Wilms tumors are one of types of tumors that are more commonly linked to hemihypertrophy. The Wilms tumor usually develops before the age of 5, but some children can develop them later.
Children with hemihypertrophy also have an increased risk of developing a liver cancer called hepatoblastoma. Most hepatoblastomas develop by 2 years old.
The importance of regular cancer screenings
Given the importance of early detection, all children with hemihypertrophy should receive cancer screenings, which consists of an abdominal ultrasound every 3 to 4 months until the age of 10.
If we detect a developing Wilms tumor, we usually start treatment with a low dosage of chemotherapy to slow the tumor's growth. This treatment is followed by a partial nephrectomy in which we remove the affected part of the kidney, taking care to save as much of the kidney as possible.
Why choose us for treatment of hemihypertrophy?
Children's Colorado has medical specialists experienced in treating all types of tumors related to hemihypertrophy. From our Surgical Oncology Program that diagnoses, monitors and treats hemihypertrophy-related tumors, to our Genetics and Inherited Metabolic Diseases Program that helps to diagnose related genetic diseases, we work in close collaboration to care for every one of your child's needs. We also work closely with our Vascular Anomalies Center if the particular case of hemihypertrophy is related to a vascular malformation. Having a multidisciplinary team in one location helps us treat this complex condition while easing the burden on you and your child.
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