Hemihyperplasia, formerly called hemihypertrophy, is a rare disorder in which one side of the body
grows more than other, causing asymmetry.
In a normal cell, there is a mechanism that turns off growth once the
cell reaches a certain size. However, in hemihypertrophy, the cells on one side
aren’t able to stop growing. This causes the body to continue growing or
enlarge abnormally. This disorder is congenital, which means that it is evident
No one is sure what causes hemihyperplasia, but there is
some evidence that this disease runs in families. Genetics seems to play a
role, but the genes that seem to cause hemihyperplasia can differ from person
to person. A mutation on gene 11 is suspected to be the cause.
How Many People are Diagnosed with Hemihyperplasia?
Statistics vary on how many people actually have this
disorder. There are several reasons for this. First, the symptoms of
hemihyperplasia are similar to other diseases, so sometimes the diagnosis can
be confused with other diseases. Also, sometimes the asymmetry or overgrowth of
one side can be so slight that it isn’t easily recognizable. Hemihyperplasia
affects approximately 1 in 13,200 births, though other research indicates about
1 in 86,000 births (Beck, 1968, Parker 1969).
What Are the Symptoms?
The most obvious symptom of hemihyperplasia is the tendency
for one side of the body to be larger than the other side. An arm or a leg can
be longer or larger in circumference. In some cases, the trunk or the face on
one side is larger. Sometimes this isn’t really noticeable unless the
individual lies on a bed or flat surface (called the bed test). In other cases
the difference in posture and gait (how someone walks) is very obvious.
Children with hemihyperplasia are at an increased risk for
tumors, specifically those that occur in the abdomen. Wilms tumors, which occur
in the kidneys, are the most common. Tumors are an abnormal cancerous growth
that can be benign (harmless) or malignant (harmful). Like hemihyperplasia, the
cells that form a tumor have often lost the ability to stop or “turn off” the
growth mechanism. Other types of tumors
that are associated with hemihyperplasmia are hepatoblastomas (tumor of the liver), adrenal cell carcinomas, and leiomyosarcomas
(tumor of the muscle tissue).
How Is it Diagnosed?
A diagnosis is usually made by a physical exam. Symptoms of
this disease are associated with other diseases, like Beckwith-Wiedemann syndrome (BWS), Proteus syndrome, Russell-Silver
syndrome, and Sotos syndrome. Before
diagnosing, your health care provider should rule out these diseases. They may
also order radiologic exams to screen for tumors.
Because this disorder is rare and often overlooked, it is
recommended that the diagnosis be made by a clinical geneticist who is familiar
with the syndrome.
How Is it Treated?
There is no cure for this disorder. Treatment is centered on
screening the patient for tumor growth and treating the tumors. For abnormal
limbs size, orthopedic treatment and corrective shoes can be recommended.
What Else Do I Need to Know?
If you think your child has hemihyperplasia or if you have a
diagnosis, you should also consider the following:
- Get a referral to a clinical geneticist for
- Know your doctor’s plan for tumor surveillance.
Some guidelines recommend screening for tumors for the first six years. Others
recommend abdominal ultrasounds every three months until the age of 7.
- Consult the doctor in whether a serum
alpha-fetoprotein (SAF) measurement should be taken. Some guidelines recommend
that the SAF level be measured every three months until the age of 4. In some
cases, the SAF, a type of protein, is very high in infants with
If your child is
diagnosed with hemihyperplasia, it is a good idea to regularly perform an abdominal
examination of your child. Ask your doctor for recommendations on how to do
this. Parental involvement in treatment has shown to be effective in some