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Familial dysautonomia (also known as FD or Riley-Day syndrome) is a rare genetic disease that primarily afflicts Jews of Eastern European descent, with a carrier frequency of approximately 1 in 27. The carrier frequency among the general public is 1 in 3000. If both parents are carriers, the chance that their child will be afflicted with the disease is 1 in 4.
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Affected individuals possess a mutation in the IKBKAP gene on chromosome 9. The gene encodes for the IKAP protein, and it is the decreased level of IKAP protein in cells that causes familial dysautonomia. Researchers have identified three different mutations in IKBKAP in FD sufferers, and nearly all possess two copies of the most common mutation.
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Familial dysautonomia causes the autonomic and sensory nervous systems to malfunction, resulting in an incomplete development of the nerve fibers of these systems. The autonomic nervous system controls bodily functions such as the regulation of body temperature and blood pressure, swallowing and digestion, breathing in the absence of insufficient oxygen, safe stress responses, and overflow tears when one cries. The sensory nervous system regulates taste, perceptions of heat and cold, and pain reactions.
Children born with familial dysautonomia generally exhibit symptoms at a very young age, sometimes as young as 7 months. The most obvious symptom of familial dysautonomia is the lack of overflow tears that normally accompany emotional crying. Other telltale signs include a weak sucking reflex and poor muscle tone, misdirected swallowing, and blotchy skin. Older children with familial dysautonomia might exhibit symptoms such as: poor growth and failure to thrive; extensive sweating and/or drooling; puffy, reddish hands; blunted ability to detect pain or hot or cold temperatures; erratic blood pressure; delayed speech; impaired gait and curvature of the spine; smooth tongue; frequent lung infections; and dry eyes and corneal abrasions. Not all children with FD exhibit the same symptoms, and symptoms among children afflicted with FD will vary widely by severity and frequency.
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Prognosis and Treatment
There is no cure for FD at present, and the prognosis for those with FD is poor. 50% of patients with FD die by the age of 30. Fortunately, great strides have been made in the areas of diagnosis and treatment. As a result, the quality of life of FD patients has improved considerably and many are able to function independently. Some of the more common treatments include: artificial tears, specialized feeding techniques, daily chest physiotherapy, drug management of autonomic manifestations, orthopedic treatments, and hypotension-reducing interventions.
Familial Dysautonomia (FD)
This series describes the diseases tested for in the Ashkenazi Jewish Genetics Panel (AJGP).