Familial dysautonomia (FD), also called Riley-Day syndrome, is an inherited disorder that affects the nervous system. The nerve fibers of people born with FD don't work properly. For this reason, they have trouble feeling pain, temperature, skin pressure, and the position of their arms and legs. They can't fully experience taste.
In addition, people born with FD have a hard time regulating bodily functions, a condition called dysautonomia. These functions are managed by the autonomic nervous system -- the network of nerves that controls such "automatic" functions as breathing and sweating.
In people with FD, dysautonomia can affect many vital functions. It can cause difficulties in swallowing, digestion and passing urine. It also can interfere with the control of blood pressure, body temperature and the production of tears to keep the eyes moist.
FD primarily affects Jews of Eastern European (Ashkenazi) background. It is a genetic problem that is caused by an inherited mutation, or change, in a gene called IKBKAP. Scientists believe that a mutation in this gene interferes with the body's ability to produce a key protein necessary for nerves to develop and function normally.
FD only occurs when someone inherits two copies of the mutated or changed gene, one from each parent. If a child inherits only one copy of the mutated IKBKAP gene from one parent, and one normal gene from the other parent, he or she will be a "carrier" of FD. Although he will not show symptoms of the illness, a carrier can pass the gene to his or her children without ever even knowing that they have it.
Doctors estimate that about 1 of every 30 Ashkenazi Jews is a carrier of FD. This means that roughly 1 in every 3,600 children of Ashkenazi families is born with the disorder. In most cases, an FD carrier is unaware of the genetic problem until a close family member -- child, sibling, niece or nephew -- shows symptoms of the disorder.
Symptoms of FD usually begin during infancy and become worse with age. These symptoms can include:
Some children with FD may have repeated episodes of vomiting, called autonomic crises, which can occur every 15 to 20 minutes and can last for more than 24 hours. During these episodes, the child also may have very high blood pressure, a drenching sweat, skin blotches, pain in the abdomen, difficulty breathing and other symptoms. These episodes can be triggered by emotional or physical stress such as an infection.
Your doctor may suspect FD based on your child's symptoms, your family's Ashkenazi heritage and the results of your child's physical examination. Typical problems your doctor may find during an examination include a smooth, glossy tongue; decreased reflex response to tapping on a tendon; and the absence of overflow tears with crying.
To help confirm the diagnosis, your doctor may do histamine testing, in which a natural chemical called histamine is injected under your child's skin. Children who do not have FD will develop a small red skin bump called a wheal at the site of the histamine injection. Children with FD, however, do not have the same reaction. If no wheal develops at the histamine site, your doctor may take a sample of your child's blood and send it for genetic testing to look for the mutated IKBKAP gene.
Familial dysautonomia is a lifelong problem.
FD cannot be prevented. However, through genetic testing, people of Ashkenazi heritage can find out whether they carry the mutated IKBKAP gene before they start a family. A genetic counselor can explain a couple's risk of having a child born with FD.
In addition, special screening tests for FD are available in a small number of medical centers that focus on FD research. These centers are located in the northeastern United States and in Israel.
There is no way to correct the gene mutation that causes FD. Treatment focuses on relieving a child's symptoms and preventing complications. Treatments include:
If you have a close blood relative with FD, check with your doctor about the need for genetic testing before you start a family. Also talk to your doctor about the risk of having a child with FD if you and your spouse are both of Ashkenazi heritage.
At one time, almost everyone with FD died during childhood. Now, because of advances in medical care, many live into adulthood.
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