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HEREDITARY MONOGENIC DISEASES

           

Riley Day syndrome (Familial dysautonomia)

The Familial dysautonomia, also known as hereditary sensory and autonomic neuropathy type 3 (HSAN3) or Riley-Day syndrome, is an inherited disorder characterized by sensory dysfunction and severe impairment of the autonomic nervous system, leading to a multisystem dysfunction. It affects the development and survival of certain nerve cells.

It is an autosomal recessive disorder characterised by failure to thrive and progressive degeneration of sensory, sympathetic and parasympathetic neurons. Affected individuals have decreased sensitivity to pain and temperature, cardiovascular instability, recurrent pneumonias, vomiting crises and gastrointestinal dysfunction.

The disorder disturbs cells in the autonomic nervous system, which controls involuntary actions such as digestion, breathing, production of tears, and the regulation of blood pressure and body temperature. It also affects the sensory nervous system, which controls activities related to the senses, such as taste and the perception of pain, heat, and cold.

Riley Day syndrome symptoms

The Riley Day syndrome is present at birth and is progressive. Problems related to this disorder first appear during infancy. Early signs and symptoms include poor muscle tone (hypotonia), feeding difficulties, poor growth, lack of tears, frequent lung infections, and difficulty maintaining body temperature. Older infants and young children with familial dysautonomia may hold their breath for prolonged periods of time, which may cause a bluish appearance of the skin or lips (cyanosis) or fainting. This breath-holding behavior usually stops by age 6. Developmental milestones, such as walking and speech, are usually delayed, although some affected individuals show no signs of developmental delay.

Additional signs and symptoms in school-age children include bed wetting, episodes of vomiting, reduced sensitivity to temperature changes and pain, poor balance, abnormal curvature of the spine (scoliosis), poor bone quality and increased risk of bone fractures, and kidney and heart problems. Affected individuals also have poor regulation of blood pressure. They may experience a sharp drop in blood pressure upon standing (orthostatic hypotension), which can cause dizziness, blurred vision, or fainting. They can also have episodes of high blood pressure when nervous or excited, or during vomiting incidents. About one-third of children with Riley Day syndrome have learning disabilities, such as a short attention span, that require special education classes. By adulthood, affected individuals often have increasing difficulties with balance and walking unaided. Other problems that may appear in adolescence or early adulthood include lung damage due to repeated infections, impaired kidney function, and worsening vision due to the shrinking size (atrophy) of optic nerves, which carry information from the eyes to the brain.

Riley Day syndrome (carrier)

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Riley Day syndrome diagnosis

Your doctor may suspect Riley Day syndrome 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 Riley Day syndrome, 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.

GENE OR REGION STUDIED


  • IKBKAP