Familial Dysautonomia (Riley-Day Syndrome): A Guide for Patients and Families

Familial dysautonomia (FD), also known as Riley-Day syndrome or hereditary sensory and autonomic neuropathy type III (HSAN III), is a rare genetic disorder that affects the development and survival of autonomic and sensory neurons. It is one of the most well-characterized forms of hereditary dysautonomia and has a unique epidemiology: it occurs almost exclusively in individuals of Ashkenazi Jewish descent, in whom it is one of the most common inherited neurological diseases.

Genetics and Prevalence

Familial dysautonomia is caused by mutations in the IKBKAP gene (also called ELP1), which encodes a protein essential for the normal development and maintenance of neurons. The vast majority of FD patients (>99%) carry the same founder mutation: a splice site mutation in intron 20 of the IKBKAP gene that reduces the production of functional IKAP protein.

FD is inherited in an autosomal recessive pattern — a child must inherit two copies of the mutated gene (one from each parent) to develop the disease. Carrier frequency in the Ashkenazi Jewish population is approximately 1 in 30, giving a disease incidence of approximately 1 in 3,600 Ashkenazi Jewish births. Outside this population, FD is extremely rare.

Carrier testing for FD is included in standard Ashkenazi Jewish genetic carrier screening panels, and genetic counseling is recommended for Ashkenazi Jewish couples planning a pregnancy.

How FD Affects the Nervous System

The IKAP protein is required for the normal development and survival of neurons, particularly autonomic neurons (which control involuntary functions) and sensory neurons (which transmit pain, temperature, and other sensations). In FD, reduced IKAP production leads to a significant reduction in the number of these neurons — patients with FD are born with fewer autonomic and sensory neurons than normal, and these neurons continue to degenerate throughout life.

The consequences of this neuronal loss are widespread:

Autonomic dysfunction: The reduced number of autonomic neurons impairs virtually every autonomic function, including blood pressure regulation, heart rate control, temperature regulation, sweating, tear production, gastrointestinal motility, and bladder function.

Sensory dysfunction: Reduced sensory neurons impair pain and temperature sensation. FD patients have reduced sensitivity to pain and temperature, which means they may not feel injuries, burns, or internal pain that would alert a neurotypical person to a problem. This sensory deficit is a significant safety concern.

Absent corneal reflexes: The reflex that causes blinking when the eye is touched is absent or reduced in FD, contributing to corneal damage and vision problems.

Clinical Features

The clinical presentation of FD spans from birth through adulthood, with different features predominating at different ages.

Neonatal and infancy period:

• Feeding difficulties (poor suck, swallowing incoordination)
• Hypotonia (reduced muscle tone)
• Absent or reduced tearing (alacrima)
• Temperature instability
• Recurrent aspiration pneumonia

Childhood:

• Dysautonomic crises (see below)
• Developmental delay (particularly in motor milestones)
• Scoliosis (spinal curvature, affecting >90% of patients)
• Reduced pain and temperature sensation
• Absent deep tendon reflexes
• Orthostatic hypotension
• Gastrointestinal dysmotility (vomiting, constipation, feeding difficulties)

Adolescence and adulthood:

• Progressive neurological decline
• Worsening orthostatic hypotension
• Renal disease (from chronic hypertension and autonomic dysfunction)
• Pulmonary disease (from recurrent aspiration)
• Retinal vascular disease
• Continued scoliosis progression

Dysautonomic Crises

Dysautonomic crises are one of the most dramatic and distressing features of FD. These episodes are characterized by:

• Nausea and vomiting (often severe and prolonged)
• Hypertension (markedly elevated blood pressure)
• Tachycardia
• Profuse sweating
• Skin blotching (erythematous blotching of the skin)
• Irritability and emotional lability
• Drooling

Crises are triggered by emotional stress, illness, fatigue, or other physiological stressors and can last hours to days. They represent a state of autonomic hyperactivation — a storm of sympathetic activity — that is extremely distressing for patients and families. Hospitalization is sometimes required for severe crises.

Management of crises includes benzodiazepines (to reduce sympathetic activation), antiemetics, blood pressure management, and careful attention to hydration and nutrition during the episode.

Diagnosis

FD is diagnosed by genetic testing demonstrating the characteristic IKBKAP mutation. Clinical diagnosis is supported by the combination of:

• Ashkenazi Jewish ancestry
• Absent fungiform papillae on the tongue (the small bumps on the tongue surface that contain taste buds — these are absent in FD due to sensory neuron loss)
• Absent deep tendon reflexes
• Absent corneal reflexes
• Reduced or absent tearing
• Orthostatic hypotension without compensatory tachycardia

The intradermal histamine test — injection of histamine under the skin — produces a characteristic flare response in normal individuals (a red wheal surrounded by a larger red flare). In FD, the flare response is absent because the sensory nerve fibers that mediate it are absent.

Management

FD management is multidisciplinary and focuses on preventing complications and managing symptoms across all affected organ systems.

Orthostatic hypotension: Managed with salt and fluid loading, compression garments, fludrocortisone, and midodrine. Head-of-bed elevation reduces supine hypertension.

Dysautonomic crises: Benzodiazepines (diazepam) are the primary treatment for acute crises. Clonidine may reduce crisis frequency and severity.

Gastrointestinal: Feeding therapy, nutritional support, prokinetic agents for gastroparesis, and management of constipation. Gastrostomy tube placement may be necessary for patients with severe feeding difficulties.

Pulmonary: Aggressive management of aspiration pneumonia, chest physiotherapy, and in some cases fundoplication (surgical procedure to reduce reflux and aspiration).

Ophthalmological: Artificial tears, protective eyewear, and regular ophthalmological monitoring to prevent corneal damage.

Orthopedic: Scoliosis monitoring and surgical correction when indicated.

Renal: Blood pressure monitoring and management to prevent hypertensive renal damage.

Emerging Treatments

The most exciting development in FD research is the identification of drugs that can correct the splicing defect in the IKBKAP gene, increasing the production of functional IKAP protein. Tocotrienol (a form of vitamin E) and kinetin (a plant cytokinin) have been shown in laboratory and early clinical studies to increase IKAP protein levels in FD patient cells. Clinical trials of these and related compounds are ongoing.

Gene therapy approaches — delivering a functional copy of the IKBKAP gene to affected neurons — are also in early development and represent a potential path toward disease modification rather than symptom management alone.

The Familial Dysautonomia Foundation (www.familialdysautonomia.org) funds research and provides support resources for patients and families, and has been instrumental in advancing FD research since the 1950s.

Prognosis

The prognosis for FD has improved significantly over the past several decades due to advances in supportive care. Survival into adulthood is now common, and many patients with FD live into their 30s, 40s, and beyond. The primary causes of death are respiratory failure (from aspiration pneumonia and pulmonary disease) and renal failure. With aggressive management of these complications, life expectancy continues to improve.

The emotional and psychological impact of FD on patients and families is substantial. Living with a progressive, life-limiting genetic disease — and in many cases, caring for a child with FD — requires significant support. Patient organizations, genetic counseling, and psychological support are essential components of comprehensive FD care.

This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before making changes to your treatment plan.