Familial dysautonomia (FD) is a genetic condition that impacts the development and survival rate of nerve cells within the autonomic nervous system and the sensory nervous system. The autonomic nervous system is responsible for involuntary processes, such as breathing, digestion, blood pressure, and body temperature. The sensory nervous system governs sensations and the perception of temperature and pain. Hence, the healthy presence of these critical neurons is key.
Health problems that arise because of familial dysautonomia begin to develop during infancy and continue throughout adolescence into adulthood. Couples wanting to start a family can schedule comprehensive carrier screening to determine if they carry the genetic mutation that causes this disorder, while expectant mothers can undergo noninvasive prenatal testing (NIPT) to diagnose the baby with this condition before birth.
What Are the Symptoms of FD?
Early symptoms that appear during infancy include:
- Difficulty feeding, including gagging and choking
- Lack of tears
- Difficulty regulating body temperature
- Frequent lung infections
- Decreased reflexes
- Poor muscle tone
- Impaired growth
- Delayed developmental milestones, such as speech and walking
- Breath-holding behavior, often causing fainting
Symptoms experienced by school-aged children include:
- Vomiting episodes
- Poor balance
- Inability to sense body position, often leading to accidental injuries
- Reduced sensitivity to pain and temperature changes
- Deformed joints
- Scoliosis, or abnormal spine curvature
- Poor bone quality and a heightened risk of fractures
- Heart and kidney issues
- Difficulty regulating blood pressure, typically experienced as drastic drops in blood pressure when standing and high blood pressure when excited, nervous, or vomiting
- Learning disabilities
During adolescence or early adulthood, symptoms include:
- Balance problems
- Difficulty walking
- Delayed puberty, particularly among girls
- Lung damage from repeated infections
- Impaired kidney function
- Atrophy of optic nerves, causing vision issues
How Is FD Inherited?
Familial dysautonomia occurs due to mutations in the IKBKAP gene. These mutations hinder the body’s ability to produce the ELPI protein, necessary for the development and functioning of nerves. Almost all individuals with FD have DNA that includes two copies of the same mutation for each cell. The mutations disrupt protein production in critical brain cells and cause the symptoms of FD.
The disorder is inherited through an autosomal recessive pattern. A child must receive two copies of the mutated gene, one copy from each parent, to exhibit FD symptoms. If you inherit a mutated copy from one parent and a healthy copy from the other, you are considered a carrier of FD. A carrier does not exhibit symptoms but can pass the gene mutations on to their children. In most cases, carriers are not aware of their carrier status until a close family member displays symptoms.
Who Is at Risk for FD?
While this disorder is extremely rare within the general population, it commonly occurs in individuals of Ashkenazi Jewish descent, affecting approximately one in 3,700 individuals belonging to this group. Researchers estimate that one in 30 Ashkenazi Jews is an FD carrier. If you and your partner both have Ashkenazi heritage, your child is especially vulnerable to developing this condition.
If your family includes a close relative that suffers from FD, you should consult with your doctor about genetic testing before you decide to start a family. The only way to know for certain if you are a carrier of FD is to undergo comprehensive carrier screening.
What Should I Do If I Am a Carrier?
If your family history includes FD or a carrier screening finds that you or your partner are FD carriers, you can request noninvasive prenatal tests to determine if your growing baby has the disorder. At the end of the first trimester, your doctor can perform a chorionic villus sampling, in which they remove a small tissue sample from the placenta to examine it for the mutated IKBKAP gene. During the second trimester, your doctor can perform an amniocentesis, taking a sample of the amniotic fluid to analyze your baby’s genetics.
Even if you and your partner are both FD carriers, your baby has a 75% chance of inheriting only one copy of the mutated gene, or neither copy, meaning they will not experience FD. Performing testing provides you with peace of mind, as well as data to help inform next steps.