Familial Dysautonomia Health Article

Definition

Familial dysautonomia (FD) is a rare inherited disorder in which affected individuals experience multiple malfunctions of the autonomic nervous system (the part of the nervous system that regulates heart muscle, smooth muscle, and glands) as well as the sensory, motor, and central components of the nervous system. The disorder is progressive with a continual loss of nerve cells of the sensory and autonomic nervous systems.

Description

Familial dysautonomia is an inherited disorder that occurs almost exclusively in people of Eastern European (Ashkenazi) Jewish descent. FD is one of a larger group of at least five hereditary sensory and autonomic neuropathies (HSANs), meaning conditions that stem from abnormalities of the nervous system. FD was first described in 1949 by pediatricians Conrad Riley and Richard Day. They reported five children, all Jewish, who had an unusual set of reactions to mild anxiety, attributed to a disturbance of the autonomic nervous system. FD is also known as HSAN type III or Riley-Day syndrome. Decades of studies have determined the cause to be a genetic abnormality that causes poor development of nerve cells in the fetus, leading to a progressive loss of nerve cells of the autonomic and sensory nervous systems. The depletion of nerve cells in the autonomic system causes problems with unstable heart rate, blood pressure, and body temperature, as well as gastrointestinal dysfunction, poor motor coordination, and emotional instability. Abnormal development of the sensory nervous system results in poor perception of pain, heat, and cold. This causes affected individuals to injure themselves without being aware of it. This deterioration of the nervous system worsens throughout life and causes multiple health problems that lead to the death of 50% of those affected by adulthood.

Genetic profile

FD is caused by mutations (genetic errors) in the IKBKAP gene that is found on human chromosome 9, specifically located at region 9q31. The disease is inherited as an autosomal recessive trait. This means that both parents have one copy of the mutant gene but do not have the disease. For these parents, there is a 25% chance with each pregnancy that the child will have the disease.

The IKBKAP gene has two known mutations, which together account for 100% of the Ashkenazi Jewish (AJ) cases of FD. There is also a third mutation causing FD that is rarely seen in the non-AJ population. This mutation's gene location has not yet been determined.