Familial dysautonomia (FD), also known as Riley–Day syndrome, is a rare, progressive, recessive genetic disorder of the autonomic nervous system that affects the development and survival of sensory, sympathetic, and some parasympathetic neurons in the autonomic and sensory nervous system. FD results in variable symptoms, including insensitivity to pain, inability to produce tears, poor growth, and labile blood pressure (episodic hypertension and postural hypotension). People with FD have frequent vomiting crises, pneumonia, problems with speech and movement, difficulty swallowing, and inappropriate perception of heat, pain, and taste, as well as unstable blood pressure and gastrointestinal dysmotility. Originally reported by Drs. Conrad Milton Riley and Richard Lawrence Day in 1949, FD is one example of a group of disorders known as hereditary sensory and autonomic neuropathies (HSANs). All HSANs are characterized by widespread sensory dysfunction and variable autonomic dysfunction caused by incomplete development of sensory and autonomic neurons. The disorders are believed to be genetically distinct from each other.
Signs and symptoms Signs and symptoms of familial dysautonomia usually commence during infancy and advance with age, and may include gastrointestinal dysmotility (including erratic gastric emptying, gastroesophageal reflux, abnormal esophageal peristalsis, oropharyngeal incoordination), dysphagia (as poor suckling in infancy) and frequent choking/gagging, recurrent vomiting, poor weight gain/growth, delayed development (especially walking) and puberty (especially in girls), recurrent aspiration pneumonia (due to inhalation of food or vomitus) with possible secondary chronic lung disease, absence of overflow tears during crying, corneal ulcers, red skin blotches and excessive sweating (often during eating or excitement), breath-holding spells, slurred speech/nasal voice, tongue ulcers (from accidental self-injuries), hyporeflexia (variable absence of deep tendon reflexes), hypotonia, enuresis, arrhythmias, hypertension (including episodic hypertension in response to emotional stress or visceral pain), hypotension (including orthostatic hypertension with compensatory tachycardia (invariably present)), impaired (but not absent) temperature and pain perception (leading to frequent accidental injury), impaired proprioception, a smooth glossy tongue, scoliosis (with possibly secondary restrictive lung disease), abnormal gait, short stature, chronic renal failure (common), visual impairment, variable cognitive ability, characteristic facial features that develop with time, impaired vibration perception, lack of fungiform papilla of the tongue, and impaired taste perception (especially for sweetness).
Autonomic crises – In children with FD, recurrent episodes of vomiting may occur. Such episodes may be triggered by physical (e.g. infection) or emotional stress, may occur every 15–20 minutes for over 24 hours, and may be accompanied by significant hypertension, drenching sweat, breathing issues, fever, tachycardia, aspiration pneumonia, skin blotches, drooling, and negative personality change. Pain insensitivity – Insensitivity or indifference to painful stimuli may lead to frequent/progressive self-mutilation, burns, and ulcers. There may be self-mutilation of the tongue (especially in toddlers during teething), lips, and cheeks, or loss of teeth. Compulsive oral biting may result in ulcers or tumour-like masses (Riga–Fede disease).
Progression Familial dysautonomia presents with progressive, age-specific symptoms. Though usually not diagnosed until several years of age, generalised signs of FD are present during the newborn period in more than 80% of those affected. Dysmorphic facial features are not directly inherent to the disorder, but facial asymmetry and a straightened mouth eventually develop due to abnormal tone and molding of facial bones.
Perinatal A very high incidence of breech presentation has been noted among infants with FD. A lower birth weight as compared to siblings, premature birth, and intrauterine growth restriction have also been noted.
Neonatal During the neonatal period, hypotonia, respiratory insufficiency, poor feeding with difficulty swallowing and aspiration, developmental delay, short stature, scoliosis, and corneal disease may occur.
Infancy Issues related to the disorder first appear during infancy. Early manifestations include hypotonia, feeding difficulty (impaired swallowing and suckling), poor growth, absence of tears, frequent lung infections, and poor body-temperature control (infants may display cold hands and feet). Developmental milestones (e.g. walking, speech) may or may not be delayed. In infants with FD, a lack of overflow tears during emotional crying may be noted after the age of 7 months (until this age, overflow emotional tearing may also not occur in unaffected infants; overflow tearing is absent in neonates and begins to appear only after 2–3 months of age). Affected infants' hands may alternatively appear cool and mottled (from vasoconstriction), or red and swollen (from vasodilation). Red skin blotching is often precipitated by emotional excitement. In older infants and young children, breath-holding spells may occur, possibly leading to cyanosis or fainting. Breath-holding behaviour usually ceases by age 6.
Children In school-age children, bed wetting, vomiting episodes, impaired pain, and temperature perception, impaired blood pressure control (including orthostatic hypotension, hypertension during periods of psychological excitement or vomiting), learning disabilities (e.g. short attention span; learning disabilities are present in about a third of those with FD, and may require special education), scoliosis, poor bone quality and bone fractures, and kidney and heart issues may be seen.
Adolescence and adulthood Issues that tend to commence during adolescence or early adulthood include lung damage due to multiple respiratory infections, impaired kidney function, and impaired vision (due to atrophy of the optic nerve). By adulthood, difficulties with balance and unaided walking often arise.
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