Riley-Day Syndrome

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Inheritance

1

Autosomal Recessive HP:0000007

Familial dysautonomia is autosomal recessive. Sibs of an affected individual carry the usual 25% / 50% / 25% recurrence risks. Because essentially every patient carries the same founder allele, population-based carrier screening in people of Ashkenazi Jewish heritage is straightforward and has been widely adopted.

Autosomal recessive inheritance

Show evidence (2 references)

PMID:20301359 SUPPORT Human Clinical

"Familial dysautonomia is inherited in an autosomal recessive manner."

States the mode of inheritance.

PMID:20301359 SUPPORT Human Clinical

"each sib of an affected individual has at conception a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier"

Gives the standard autosomal recessive recurrence risks used in counselling.

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Discussions and Knowledge Gaps

3

Which Elongator activity — tRNA wobble-uridine modification, alpha-tubulin acetylation, or transcriptional elongation — is the proximate cause of neuronal death in familial dysautonomia, and does Elongator have genuinely distinct functions or one primary defect with downstream consequences?

KNOWLEDGE GAP OPEN fd_which_elongator_activity

Attached to

pathophysiology#Neuronal Elongator Complex Deficiency pathophysiology#Failed Development and Innervation of Sensory and Autonomic Neurons

The entry binds tRNA wobble-uridine modification to the Elongator deficiency node because it is the best-characterized activity, but that choice is a representative tag rather than a mechanistic verdict. ELP1 has also been implicated in exocytosis, cytoskeletal organization, axonal transport, adhesion, and migration, and the literature explicitly records that it remains unclear whether Elongator has distinct functions or whether its role in tRNA modification drives everything else. Treating the tRNA binding as the established cause of neuronal death would overstate what is known, which matters because the choice determines what a mechanism-directed therapy would target.

Show evidence (2 references)

PMID:26769677 SUPPORT BACKGROUND Human Clinical

"Currently, it is still not clear whether Elongator has distinct functions or whether its primary role in tRNA modification leads to multiple downstream events"

States the open question directly — the field has not resolved whether tRNA modification is the primary defect.

PMID:30905397 SUPPORT BACKGROUND Human Clinical

"ELP1 function has been widely investigated and has been implicated in exocytosis, cytoskeletal organization, and axonal transport, as well as cellular adhesion and migration."

Enumerates the competing candidate functions, none of which has been shown to be the proximate cause of neuronal death.

If 99.5% of patients are homozygous for the same founder allele, what accounts for the wide variation in severity between them?

KNOWLEDGE GAP OPEN fd_phenotypic_variability_one_allele

Attached to

genetic#ELP1 pathophysiology#Tissue-Specific Skipping of ELP1 Exon 20

This disease is close to a natural experiment in which genotype is held constant, so the observed severity range has to come from somewhere else. Modifier genes are the standing hypothesis, but the identity of any modifier is unknown. A second, non-exclusive candidate follows from the mechanism this entry models: because the allele is leaky and the skipping fraction varies by tissue, an individual's severity may be set by how much correctly spliced ELP1 their nervous system happens to make. Distinguishing the two matters for trial design, since ELP1 level is being used as a surrogate endpoint for target engagement.

Show evidence (2 references)

PMID:37204536 SUPPORT Human Clinical

"Although 99.5% of patients are homozygous for the founder mutation, phenotypic severity varies, suggesting that modifier genes impact expression."

States both halves of the gap — near-uniform genotype, variable phenotype — and names the modifier-gene hypothesis.

PMID:37204536 SUPPORT Human Clinical

"Patients with FD produce variable amounts of ELP1 in different tissues, with the brain producing mostly mutant transcripts."

Supports the alternative candidate — inter-individual variation in residual ELP1 production.

Splice-modulating compounds rescue proprioceptive loss, gait ataxia and retinal degeneration in the humanized TgFD9 mouse, but the only human result is a change in leukocyte ELP1 splicing. Does correcting splicing after birth in humans rescue neurological phenotypes, as it does in the mouse?

HUMAN MODEL MISMATCH OPEN fd_kinetin_mouse_to_human_gap

Attached to

animal_models#Mouse treatments#Splice-Modulating Therapy (Kinetin and Derivatives) pathophysiology#Postnatal Proprioceptive Neuron Loss

The efficacy evidence and the human evidence measure different things. In the mouse, kinetin given from birth prevents proprioceptive neuron loss and spinal abnormality, and a brain-penetrant derivative improves survival, gait ataxia, and retinal degeneration — phenotypic endpoints. In patients, the only demonstrated effect is a significant rise in wild-type ELP1 message in leukocytes over 28 days, which is target engagement in an accessible tissue, not benefit in the nervous system and not a clinical outcome. Two specific things do not transfer: leukocytes are among the tissues that mis-splice least, so a leukocyte readout is a weak proxy for the neuronal compartment that matters; and the mouse rescues begin at birth, whereas patients are typically treated later, after some of the loss has already happened. The mechanism gives a reason to expect timing to be decisive, since proprioceptors and retinal ganglion cells are the populations lost postnatally and therefore the ones still present to save.

Show evidence (3 references)

PMID:30905397 SUPPORT Model Organism

"Daily administration of kinetin starting at birth improves sensory-motor coordination and prevents the onset of spinal abnormalities by stopping the loss of proprioceptive neurons."

The mouse phenotypic rescue, obtained with treatment from birth, that the human data do not yet match.

PMID:21775922 SUPPORT Human Clinical

"This is the first report of a drug that produces in vivo mRNA splicing changes in individuals with FD and supports future long-term trials to determine whether kinetin will prove therapeutic in FD patients."

The human result is a splicing change with therapeutic benefit explicitly still to be determined, which is the mismatch.

PMID:37204536 SUPPORT Human Clinical

"Early intervention may be critical for treatment to be successful."

Supports the timing component of the gap — that when treatment starts may determine whether the mouse result transfers.

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Pathophysiology

10

ELP1 Intron 20 Donor Splice Site Weakening

The Ashkenazi founder allele is a T-to-C transition at the sixth base of ELP1 intron 20, in the donor (5') splice site of exon 20. It weakens the site without inactivating it, so it is a hypomorphic rather than a null allele — patient cells still make some correctly spliced transcript, which is why a recessive, uniformly homozygous disease nonetheless varies in severity and is a candidate for splice-modulating therapy. A minority of alleles are instead missense changes (R696P in exon 19, and P914L in exon 26, the first non-Jewish allele found).

ELP1 (formerly IKBKAP) hgnc:5959

mRNA 5'-splice site recognition at ELP1 exon 20 GO:0000395 ↓ DECREASED

Downstream

Tissue-Specific Skipping of ELP1 Exon 20 A weakened donor site is recognized by the spliceosome only some of the time, so exon 20 is skipped in a variable fraction of transcripts.

Show evidence (2 references)

PMID:11179021 SUPPORT Human Clinical

"These findings demonstrate that mutations in the gene encoding IKAP are responsible for FD."

Establishes ELP1 (IKAP) mutation as the cause of familial dysautonomia.

PMID:12687659 SUPPORT Human Clinical

"Interestingly, despite the fact that FD is a recessive disease, normal mRNA and protein are expressed in patient cells."

Documents that the founder allele is leaky — patient cells retain some correctly spliced product — which is the premise of splice-modulating therapy.

Tissue-Specific Skipping of ELP1 Exon 20

Exon 20 skipping produces a frameshifted, truncated transcript. Crucially the skipping fraction differs by tissue: the nervous system produces mostly mutant transcript while fibroblasts and other non-neuronal tissue produce close to equal amounts of wild-type and mutant message. This tissue selectivity, not the mutation's severity, is what makes an otherwise ubiquitously expressed housekeeping gene cause a purely neurological disease.

ELP1 (formerly IKBKAP) hgnc:5959

Animal models

TgFD9;Elp1 humanized familial dysautonomia mouse Mouse recapitulates The transgene reproduces the same tissue-specific exon 20 mis-splicing seen in patients, which is the property the model was built for.

Downstream

Neuronal Elongator Complex Deficiency Because the skipped transcript is frameshifted and non-functional, the nervous system's high skipping fraction translates into a low neuronal concentration of ELP1 protein and therefore of assembled Elongator.

Show evidence (2 references)

PMID:26769677 SUPPORT BACKGROUND Human Clinical

"the relative amount of MU and WT IKBKAP transcripts varies between tissues, with the lowest levels of WT IKBKAP mRNA and IKAP protein in tissues from the central and peripheral nervous system"

Establishes the tissue gradient of mis-splicing — lowest wild-type message in nervous tissue — quoted from this mouse paper's account of the human molecular defect.

PMID:21775922 SUPPORT BACKGROUND Human Clinical

"the splicing abnormality primarily affects neuronal tissue, which produces mostly the shortened or mutant IKBKAP mRNA and a minimal amount of functional protein product"

Independently states that mis-splicing is concentrated in neuronal tissue, leaving it with minimal functional protein.

Neuronal Elongator Complex Deficiency

ELP1 is the scaffolding subunit of the six-subunit Elongator complex. Its depletion in neurons compromises the complex's known activities — transcriptional elongation, acetylation of cytoskeletal alpha-tubulin, and tRNA wobble-uridine modification. Which of these is the proximate cause of neuronal death is not settled; tRNA modification is the best-characterized activity and is tagged here as the representative process, but the cytoskeletal and trafficking roles are equally implicated and the field has not resolved whether Elongator has genuinely distinct functions or whether one primary defect produces the rest.

ELP1 (formerly IKBKAP) hgnc:5959

tRNA wobble uridine modification GO:0002098 ↓ DECREASED

Elongator complex tRNA-modifying activity GO:0140101 ↓ DECREASED

Downstream

Failed Development and Innervation of Sensory and Autonomic Neurons Elongator deficiency impairs neurogenesis, target-tissue innervation, and neuronal survival. The intermediate steps between the biochemical deficit and the cellular failure are not established, which is why this edge is typed as having unknown intermediates.

Show evidence (3 references)

PMID:30905397 SUPPORT BACKGROUND Human Clinical

"ELP1 is the scaffolding member of the six-subunit human Elongator complex"

Establishes ELP1's role as the complex's scaffolding subunit, so its depletion is an Elongator deficiency.

PMID:26769677 SUPPORT BACKGROUND Human Clinical

"The Elongator complex is an evolutionary highly conserved protein complex that participates in distinct cellular processes, including transcriptional elongation, acetylation of cytoskeletal"

Enumerates the Elongator activities compromised by ELP1 depletion, including the tRNA modification tagged on this node.

PMID:30905397 SUPPORT BACKGROUND In Vitro

"which is a highly conserved protein complex that participates in distinct cellular processes including transcriptional elongation, acetylation of cytoskeletal α-tubulin, and tRNA modification"

Names tRNA modification among the Elongator complex's characterized activities, which is the catalytic-activity-on-a-tRNA molecular function bound on this node. Graded IN_VITRO because the quoted sentence reports the biochemical characterization of the complex rather than a clinical or whole-animal observation, and BACKGROUND because it sits in this mouse study's introduction restating established work.

Failed Development and Innervation of Sensory and Autonomic Neurons

Sensory, sympathetic, and parasympathetic neurons are generated in insufficient numbers and fail to innervate their targets. This is a developmental lesion present at birth, which is what distinguishes familial dysautonomia from the adult-onset, length-dependent dying-back neuropathies: the deficit in nociceptive and autonomic neurons predates symptoms rather than accumulating from them. Proprioceptors are the exception and arise normally.

Sensory neuron CL:0000101 Autonomic neuron CL:0000107

peripheral nervous system neuron development GO:0048935 ↓ DECREASED

Animal models

TgFD9;Elp1 humanized familial dysautonomia mouse Mouse recapitulates The mouse shows sensory and sympathetic impairment and a reduced number of fungiform papillae, the developmental readouts of this node.

Downstream

Absence of Fungiform Papillae Fungiform papillae carry gustatory and somatosensory receptors whose innervation never forms, so the papillae themselves do not develop. This edge is why the sign is present from infancy and is diagnostically useful in a newborn.

Alacrima Parasympathetic secretomotor innervation of the lacrimal gland fails to develop, so overflow tearing is absent from birth.

Progressive Sensory and Autonomic Neuron Depletion A population that starts numerically deficient and then degenerates throughout life arrives at severe depletion; the developmental failure sets the starting point for the lifelong attrition.

Show evidence (2 references)

PMID:624961 SUPPORT Human Clinical

"Intrauterine development and postnatal maintenance of dorsal root ganglion neurons are abnormal in familial dysautonomia"

Autopsy neuropathology establishes that the dorsal root ganglion lesion begins in utero rather than being purely degenerative.

PMID:30905397 SUPPORT Model Organism

"showed that although Elp1 was required for the development of the pain- and temperature-receptive neurons, proprioceptors arise and differentiate normally"

Neural-crest conditional knockout data separate the developmental lesion (nociceptors) from the postnatal one (proprioceptors), the distinction this node records.

Progressive Sensory and Autonomic Neuron Depletion

Dorsal root ganglia are markedly depleted of neurons even in the youngest patients and lose more with age, and the spinal afferent pathways they feed are correspondingly denuded. This is the single lesion from which almost every clinical feature of the disease follows, and the quantitative neuropathology is unusually stark: roughly a tenth of the expected neuron count in a cervical dorsal root ganglion.

Dorsal root ganglion sensory neuron CL:1001451

neuron death GO:0008219 ↑ INCREASED

Downstream

Afferent Baroreflex and Chemoreflex Failure Baroreceptor and chemoreceptor traffic reaches the brainstem through glossopharyngeal and vagal afferents; losing those afferent neurons removes the input side of both reflex arcs.

Postnatal Proprioceptive Neuron Loss Proprioceptors are part of the same dorsal root ganglion population, but unlike nociceptors they are generated normally and are lost only after birth.

Retinal Ganglion Cell Degeneration Retinal ganglion cells are a further ELP1-dependent projection neuron population that dies postnatally, thinning the retinal nerve fiber layer.

Enteric Nervous System Dysfunction The enteric nervous system is another ELP1-dependent neural-crest derivative whose formation and maintenance fail, producing the near universal gastrointestinal dysfunction.

Impaired Pain and Temperature Sensation Nociceptive and thermoreceptive dorsal root ganglion neurons are the population most deficient from birth, so the corresponding sensory modalities are blunted from infancy.

Neurogenic Dysphagia and Recurrent Aspiration Loss of oropharyngeal sensory afferents and of the autonomic control of swallowing produces an incoordinate, unprotected swallow.

Show evidence (3 references)

PMID:624961 SUPPORT Human Clinical

"Neurons in dorsal root ganglia are found to be markedly diminished in the youngest patients and slow degeneration causes further depletion with age."

Direct human neuropathological evidence for both the early deficit and the lifelong progression.

PMID:624961 SUPPORT Human Clinical

"Quantitative studies on C8 dorsal root ganglia show the normal neuron content to be between 42,500 and 53,600. In 3 patients with familial dysautonomia the range was 4,090-8,590 with the smallest number being in the oldest patient."

Quantifies the depletion and shows the smallest count in the oldest patient, the progression this node asserts.

PMID:624961 SUPPORT Human Clinical

"Lateral root entry zones and Lissauer's tracts are severely depleted of axons."

Shows the central projections of the depleted dorsal root ganglion neurons are correspondingly lost.

Afferent Baroreflex and Chemoreflex Failure

Loss of the afferent limb of the baroreflex leaves blood pressure without feedback control, producing both orthostatic hypotension and unopposed sympathetic surges. The parallel loss of chemoreceptor afferents abolishes the ventilatory response to hypoxia and blunts it to hypercapnia, so hypoxia produces paradoxical hypoventilation with hypotension and bradycardia instead of the normal defensive response. The efferent sympathetic apparatus is comparatively intact, which is why the failure manifests as uncontrolled output rather than as absent output.

Downstream

Dysautonomic Crises Without baroreceptor feedback, sympathetic outflow is not restrained, and the resulting catecholamine surge is the crisis.

Sleep-Disordered Breathing Chemoreflex failure matters most during sleep, when the conscious override of respiratory drive is withdrawn.

Blood Pressure Instability An open-loop pressure control system swings between orthostatic hypotension and paroxysmal hypertension.

Show evidence (3 references)

PMID:30890343 SUPPORT Human Clinical

"In patients with familial dysautonomia, ventilatory responses to hypercapnia are reduced, and to hypoxia are almost absent."

Quantifies the chemoreflex lesion — hypoxic response essentially abolished, hypercapnic response reduced.

PMID:30890343 SUPPORT Human Clinical

"In response to hypoxia, these patients develop paradoxical hypoventilation, hypotension, bradycardia, and potentially, death."

Documents the paradoxical, potentially fatal response to hypoxia that follows chemoreflex failure.

PMID:25323828 SUPPORT Human Clinical

"Patients have dramatic blood pressure instability due to baroreflex failure, chronic kidney disease, and impaired swallowing leading to recurrent aspiration pneumonia, which results in chronic lung disease."

Attributes the blood-pressure instability specifically to baroreflex failure.

Postnatal Proprioceptive Neuron Loss

Muscle-spindle afferents are lost after birth, removing proprioceptive feedback. This is the mechanistic origin of three features that look unrelated clinically — areflexia, gait ataxia, and kyphoscoliosis — since the stretch reflex arc, balance, and the postural control of the growing spine all depend on the same afferent signal. Because these neurons are present at birth and lost later, they are the population most plausibly rescuable by a postnatal splice-modulating drug.

Proprioceptive dorsal root ganglion neuron CL:1001451

Animal models

TgFD9;Elp1 humanized familial dysautonomia mouse Mouse recapitulates The model reproduces the proprioceptive impairment seen in patients, and postnatal kinetin prevents the proprioceptive neuron loss and the spinal abnormalities that follow it — a rescue experiment that is also the strongest available evidence for the causal direction of this node.

Downstream

Gait Ataxia

Areflexia

Kyphoscoliosis Poor proprioceptive control of trunk posture during growth produces the early-onset spinal deformity.

Show evidence (2 references)

PMID:30905397 SUPPORT BACKGROUND Human Clinical

"A lack of afferent signaling from the muscle spindles accounts for the absence of deep tendon reflexes and for gait ataxia."

Links muscle-spindle afferent loss to both areflexia and gait ataxia, two of this node's three downstream targets.

PMID:30905397 SUPPORT BACKGROUND Human Clinical

"Clinically, many of the debilitating aspects of the disease are related to a progressive loss of proprioception; this loss leads to severe gait ataxia, spinal deformities, and respiratory insufficiency due to neuromuscular incoordination."

Establishes proprioceptive loss as progressive and as the common origin of gait ataxia and spinal deformity.

Retinal Ganglion Cell Degeneration

Retinal ganglion cells die progressively, thinning the retinal nerve fiber layer and the macular ganglion cell and inner plexiform layers. The resulting optic neuropathy is neuro-ophthalmic rather than corneal in origin — it occurs in patients with no corneal complications at all — which distinguishes it from the separate dry-eye and corneal disease that alacrima causes.

Retinal ganglion cell CL:0000740

Animal models

TgFD9;Elp1 humanized familial dysautonomia mouse Mouse recapitulates The same mouse develops a progressive retinal phenotype, which was characterized specifically to support development of therapies for the optic neuropathy.

Downstream

Progressive Optic Neuropathy

Show evidence (2 references)

PMID:34908112 SUPPORT BACKGROUND Human Clinical

"recent detailed studies have shown that decreased visual acuity, loss of central vision and temporal optic nerve pallor occur in FD patients even without any corneal complications, suggesting a neuro-ophthalmic nature of the disease"

Establishes that the visual loss is neuro-ophthalmic and not secondary to the corneal disease of alacrima.

PMID:33180192 SUPPORT Human Clinical

"The rate of change for average RNFL and average GCIPL thicknesses were significant before reaching a plateau at the age of 26.2 for RNFL and 24.8 for GCIPL"

Longitudinal OCT in 91 patients quantifies the progressive retinal ganglion cell layer loss and shows it plateaus in the mid-twenties.

Enteric Nervous System Dysfunction

Enteric neurons are reduced and mucosal and smooth-muscle innervation is abnormal, giving dysmotility and gastroesophageal reflux. A mouse in which Elp1 was deleted only in neurons still developed a disorganized mucus layer and bacterial infiltration of the mucosa, so the epithelial barrier defect is downstream of the neuronal lesion rather than a parallel effect of ELP1 loss in epithelium.

Autonomic (enteric) neuron CL:0000107

Downstream

Gastrointestinal Dysmotility

Show evidence (2 references)

PMID:39138000 SUPPORT Model Organism

"The fact that deletion of Elp1 exclusively in neurons is sufficient to alter the intestinal epithelium and perturb the intestinal epithelial barrier highlights a critical role for neurons in regulating GI epithelium homeostasis."

Neuron-restricted deletion shows the epithelial barrier defect is a consequence of the enteric neuronal lesion.

PMID:39138000 SUPPORT BACKGROUND Human Clinical

"Virtually all patients report gastrointestinal (GI) dysfunction"

Establishes that gastrointestinal dysfunction is essentially universal in patients.

Neurogenic Dysphagia and Recurrent Aspiration

Impaired swallowing, itself a consequence of the sensory and autonomic lesion in the oropharynx and of gastroesophageal reflux, leads to repeated aspiration. This is the pathway to chronic lung disease and one of the leading causes of death, and it is the node most amenable to prevention by feeding and airway management.

Downstream

Recurrent Aspiration Pneumonia and Chronic Lung Disease

Show evidence (2 references)

PMID:37204536 SUPPORT Human Clinical

"Neurogenic dysphagia causes frequent aspiration leading to chronic pulmonary disease."

States the chain from neurogenic dysphagia through aspiration to chronic lung disease.

PMID:25323828 SUPPORT Human Clinical

"Managing neurogenic dysphagia with effective protection of the airway passages and prompt treatment of aspiration pneumonias is necessary to prevent respiratory failure."

Identifies this node as the intervention point that prevents respiratory failure.

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Pathograph

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Phenotypes

19

Cardiovascular 2

Dysautonomic Crises Episodic hypertension HP:0000875

Sequelae: Cyclic Vomiting

Show evidence (2 references)

PMID:37204536 SUPPORT Human Clinical

"consisting of brisk episodes of severe hypertension, tachycardia, skin blotching, retching, and vomiting occur in all patients"

Describes the crisis phenotype and establishes that it occurs in every patient.

PMID:36381719 SUPPORT Human Clinical

"The features of dysautonomic crises are hypertension, tachycardia, vomiting, sweating, flushing, and behavioral changes."

Enumerates the crisis features, including the sweating, flushing, and behavioural change.

Blood Pressure Instability Orthostatic hypotension due to autonomic dysfunction HP:0004926

Sequelae: Chronic Kidney Disease

Show evidence (2 references)

PMID:37204536 SUPPORT Human Clinical

"Patients have excessive blood pressure variability due to the failure of the IXth and Xth cranial nerves to carry baroreceptor signals."

Attributes the blood-pressure variability to failure of the baroreceptor afferents.

PMID:20301359 SUPPORT Human Clinical

"Pregnancies in women with FD are considered high risk because of blood pressure lability."

Documents blood-pressure lability and its consequence for pregnancy management.

Digestive 2

Cyclic Vomiting Episodic vomiting HP:0002572

Show evidence (1 reference)

PMID:20301359 SUPPORT Human Clinical

"autonomic crises (i.e., hypertensive vomiting attacks)"

GeneReviews defines the autonomic crisis in terms of its hypertensive vomiting attacks.

Gastrointestinal Dysmotility HP:0002579

Show evidence (2 references)

PMID:21775922 SUPPORT BACKGROUND Human Clinical

"as well as gastrointestinal dysmotility"

Names gastrointestinal dysmotility among the characteristic features.

PMID:26769677 SUPPORT BACKGROUND Human Clinical

"Common symptoms include gastrointestinal dysfunction, gastroesophageal reflux, vomiting crises, recurrent pneumonia"

Lists gastrointestinal dysfunction and reflux among the common symptoms.

Eye 3

Alacrima HP:0000522

Sequelae: Corneal Opacity and Neurotrophic Keratopathy

Show evidence (2 references)

PMID:21775922 SUPPORT BACKGROUND Human Clinical

"Affected patients have characteristic alacrima, depressed tendon reflexes and decreased pain and temperature perception, as well as gastrointestinal dysmotility"

Names alacrima as a characteristic feature alongside the other cardinal signs.

PMID:26769677 SUPPORT BACKGROUND Human Clinical

"absence of fungiform papillae on the tongue, decreased deep-tendon reflexes, defective lacrimation and impaired pain and temperature perception"

Lists defective lacrimation among the common clinical features of the disease.

Progressive Optic Neuropathy Optic atrophy HP:0000648

Course: PROGRESSIVE

Show evidence (3 references)

PMID:34908112 SUPPORT BACKGROUND Human Clinical

"In FD, visual impairment is usually early onset and often progresses to legal blindness in the third decade of life"

Gives the onset and the usual endpoint of the visual phenotype.

PMID:20301359 SUPPORT Human Clinical

"Optic neuropathy results in progressive vision loss."

GeneReviews states the optic neuropathy and its progressive course.

PMID:9176780 SUPPORT Human Clinical

"Optic atrophy, which is indicative of a CNS disorder, is a rarely described manifestation of familial dysautonomia (Riley-Day syndrome)."

An early report of optic atrophy in this disease, before longer survival made it a routinely recognized feature.

Corneal Opacity and Neurotrophic Keratopathy FREQUENT HP:0007957

Show evidence (3 references)

PMID:25323828 SUPPORT Human Clinical

"Corneal opacities, neurotrophic keratopathy (i.e., corneal damage as a result of poor tear secretion and corneal hypoesthesia)"

Establishes both the phenotype and its dual mechanism — deficient tear secretion together with corneal hypoesthesia.

PMID:25323828 SUPPORT Human Clinical

"Severe corneal opacities occur in around 30% of FD patients."

Source for the frequency value. 30% falls in the FREQUENT band (30-79%). Note the reported figure is for *severe* opacities, so FREQUENT is a floor for corneal opacity of any grade rather than an estimate of it.

PMID:25323828 SUPPORT Human Clinical

"Some cases may require corneal transplant, but success rates are low due to poor wound healing and epithelial defects."

Supports the claim that transplant is a poor salvage in this disease specifically, because healing and epithelium are themselves affected.

Genitourinary 1

Chronic Kidney Disease FREQUENT HP:0012622

Course: PROGRESSIVE

Show evidence (5 references)

PMID:25323828 SUPPORT Human Clinical

"Patients have dramatic blood pressure instability due to baroreflex failure, chronic kidney disease, and impaired swallowing leading to recurrent aspiration pneumonia, which results in chronic lung disease."

Names chronic kidney disease among the cardinal organ complications of the disease.

PMID:25323828 SUPPORT Human Clinical

"Chronic renal failure is a frequent problem in patients with FD."

Source for the frequency value. Author wording "frequent" maps to FREQUENT under the dismech qualitative mapping (docs/frequency-evidence-guidelines.md Pattern C). No percentage or cohort denominator is reported for renal failure in this review.

PMID:25323828 SUPPORT Human Clinical

"Sustained supine hypertension is usually present in FD patients with advanced chronic kidney disease"

Establishes the reverse arm of the relationship — advanced renal disease brings sustained supine hypertension, not only lability.

+ 2 more references

Head and Neck 1

Absence of Fungiform Papillae Abnormal tongue morphology HP:0030809

Show evidence (2 references)

PMID:14245781 SUPPORT Human Clinical

"No fungiform papillae could be found on the tongues of 30 patients with familial dysautonomia. In ten of these patients a search for vallate papillae was made, but none were found."

Direct observation establishing the absence of fungiform papillae in every patient examined.

PMID:14245781 SUPPORT Human Clinical

"Inspection of the tongue may thus be useful for diagnosing this rare disease, even in infants."

Supports the diagnostic use of the sign, including in infancy.

Immune 1

Recurrent Aspiration Pneumonia and Chronic Lung Disease HP:0002100

Show evidence (2 references)

PMID:25323828 SUPPORT Human Clinical

"impaired swallowing leading to recurrent aspiration pneumonia, which results in chronic lung disease"

States the chain from impaired swallowing through recurrent aspiration pneumonia to chronic lung disease.

PMID:30905397 SUPPORT BACKGROUND Human Clinical

"Unexplained sudden death, aspiration pneumonias, and respiratory insufficiency remain the leading causes of death."

Establishes aspiration pneumonia among the leading causes of death.

Musculoskeletal 3

Neuropathic Joints and Thermal Injuries Neuropathic arthropathy HP:0002821

Show evidence (1 reference)

PMID:25323828 SUPPORT Human Clinical

"Diminished pain and temperature perception result in neuropathic joints and thermal injuries."

States the causal step from the sensory deficit to neuropathic joints and thermal injury.

Kyphoscoliosis HP:0002751

Show evidence (1 reference)

PMID:30905397 SUPPORT BACKGROUND Human Clinical

"Individuals with FD have decreased sensitivity to pain and temperature sensation, visual loss, kyphoscoliosis, proprioceptive ataxia, and difficulties in regulating body temperature."

Lists kyphoscoliosis among the clinical features alongside the proprioceptive ataxia it shares an origin with.

Hypotonia with Delayed Motor Milestones HP:0001252

Show evidence (1 reference)

PMID:20301359 SUPPORT Human Clinical

"Hypotonia contributes to delay in acquisition of motor milestones."

GeneReviews states both the hypotonia and its developmental consequence.

Nervous System 5

Impaired Pain and Temperature Sensation Impaired pain sensation HP:0007328

Sequelae: Neuropathic Joints and Thermal Injuries Corneal Opacity and Neurotrophic Keratopathy

Show evidence (2 references)

PMID:624961 SUPPORT Human Clinical

"Temperature sensation is markedly impaired from infancy in familial dysautonomia. Loss of pain sensation is prominent and worsens with age."

Separates the congenital temperature deficit from the progressive pain loss, and correlates both with the dorsal root ganglion neuron counts in the same study.

PMID:20301359 SUPPORT Human Clinical

"Affected individuals have gastrointestinal dysfunction, autonomic crises (i.e., hypertensive vomiting attacks), recurrent pneumonia, altered pain sensitivity, altered temperature perception, and blood pressure instability."

GeneReviews lists altered pain and temperature perception among the defining clinical features.

Sleep-Disordered Breathing Sleep apnea HP:0010535

Sequelae: Sudden Unexpected Death During Sleep

Show evidence (2 references)

PMID:30890343 SUPPORT Human Clinical

"Overall, almost all adult (85%) and pediatric (95%) patients have some degree of sleep-disordered breathing."

Quantifies the near-universal prevalence in both age groups.

PMID:30890343 SUPPORT Human Clinical

"Obstructive apnea events are more frequent in adults, whereas central apnea events are more severe and frequent in children."

Documents the age-dependent obstructive-versus-central pattern this phenotype records.

Gait Ataxia Sensory ataxia HP:0010871

Course: PROGRESSIVE

Show evidence (2 references)

PMID:20301359 SUPPORT Human Clinical

"Older individuals often have a broad-based and ataxic gait that deteriorates over time."

Documents the broad-based ataxic gait and its progression.

PMID:37204536 SUPPORT Human Clinical

"Progressive features of the disease include retinal nerve fiber loss and blindness, and proprioceptive ataxia with severe gait impairment."

Identifies the ataxia as proprioceptive and groups it with the other progressive features.

Areflexia HP:0001284

Show evidence (1 reference)

PMID:30890343 SUPPORT Human Clinical

"Impaired development of primary sensory nerves results in reduced pain and temperature sensation, absent deep tendon reflexes and gait ataxia"

Attributes absent deep tendon reflexes to the primary sensory nerve lesion.

Developmental Delay and Intellectual Disability OCCASIONAL HP:0001249

Show evidence (1 reference)

PMID:20301359 SUPPORT Human Clinical

"Developmental delay / intellectual disability occur in about 21% of individuals."

Quantifies the proportion affected, supporting this as a minority rather than a defining feature.

Constitutional 1

Sudden Unexpected Death During Sleep Sudden death HP:0001699

Show evidence (3 references)

PMID:28521050 SUPPORT Human Clinical

"Sudden unexpected death during sleep (SUDS) is the most common cause of death in patients with familial dysautonomia (FD)"

Establishes sudden death during sleep as the leading cause of death.

PMID:28521050 SUPPORT Human Clinical

"participants with SUDS were more likely to be receiving treatment with fludrocortisone (odds ratio [OR]; 95% confidence interval) (OR 29.7; 4.1-213.4), have untreated obstructive sleep apnea (OR 17.4; 1.5-193), and plasma potassium levels <4 mEq/L (OR 19.5; 2.36-161) but less likely to use..."

Gives the case-control risk estimates behind the modifiable-risk claim.

PMID:30890343 SUPPORT Human Clinical

"The annual incidence rate of sudden death during sleep in patients with familial dysautonomia is 3.4 per 1000 person-year, compared to 0.5-1 per 1000 person-year of sudden unexpected death in epilepsy."

Quantifies the incidence and benchmarks it against sudden unexpected death in epilepsy.

🧬

Genetic Associations

1

ELP1 (Causal)

Gene: ELP1 (formerly IKBKAP) hgnc:5959

Show evidence (5 references)

PMID:11179021 SUPPORT Human Clinical

"These findings demonstrate that mutations in the gene encoding IKAP are responsible for FD."

Establishes ELP1 (IKAP) as the causal gene.

PMID:11179021 SUPPORT Human Clinical

"In individuals bearing a minor FD haplotype, a missense mutation in exon 19 disrupts a consensus serine/threonine kinase phosphorylation site. This mutation results in defective phosphorylation of IKAP."

Documents the minor-haplotype missense allele and its functional consequence.

PMID:12687659 SUPPORT Human Clinical

"In this report, we describe the first non-Jewish IKBKAP mutation, a proline to leucine missense mutation in exon 26, P914L."

Reports the P914L allele found outside the Ashkenazi Jewish population.

+ 2 more references

🗃️

External Assertions

2

OMIM familial dysautonomia phenotype record

OMIM disease record OMIM:223900

OMIM phenotype record for familial dysautonomia (Riley-Day syndrome, HSAN III).

OMIM ELP1 gene record

OMIM gene record OMIM:603722

OMIM gene record for ELP1 (elongator acetyltransferase complex subunit 1, formerly IKBKAP).

💊

Medical Actions

12

Dysautonomic Crisis Management with Benzodiazepines and Clonidine

Action: Pharmacotherapy NCIT:C15986

Agent: diazepam CHEBI:49575 clonidine CHEBI:46631

Platform: Small molecule

Benzodiazepines and clonidine are the conventional first-line treatment for a dysautonomic crisis, aimed at damping the catecholamine surge that baroreflex failure permits. Sedatives must be used cautiously because of the risk of respiratory depression in patients who already have chemoreflex failure.

Mechanism Target:

INHIBITS Dysautonomic Crises — These agents act on the sympathetic surge itself, not on the missing afferent input, so they abort crises without altering the underlying baroreflex lesion.

Show evidence (1 reference)

PMID:36381719 SUPPORT Human Clinical

"The mainstay of treatment for dysautonomic crises is benzodiazepines and clonidine."

Establishes benzodiazepines and clonidine as the standard crisis treatment.

Show evidence (2 references)

PMID:25323828 SUPPORT Human Clinical

"Therapeutic focus on FD is centered on reducing the catecholamine surges caused by baroreflex failure."

States the therapeutic rationale this treatment implements.

PMID:25323828 SUPPORT Human Clinical

"Sedative medications should be used cautiously due to the risk of respiratory depression."

Documents the respiratory-depression caution recorded in this treatment's description.

Dexmedetomidine for Refractory Dysautonomic Crisis

Action: Pharmacotherapy NCIT:C15986

Agent: dexmedetomidine CHEBI:4466

Platform: Small molecule

An alpha-2 agonist used off-label when a crisis does not respond to benzodiazepines and clonidine. The evidence is case-level: a 19-year-old whose crisis had failed oral and intravenous labetalol, diazepam and clonidine resolved within hours of intravenous dexmedetomidine. This is a single reported case, not a trial result.

Mechanism Target:

INHIBITS Dysautonomic Crises — Central alpha-2 agonism reduces sympathetic outflow, the step that baroreflex failure leaves unrestrained.

Show evidence (1 reference)

PMID:36381719 SUPPORT Human Clinical

"He was then treated with intravenous dexmedetomidine, and his symptoms resolved within a few hours."

The observed crisis resolution on which this treatment claim rests.

Show evidence (1 reference)

PMID:36381719 SUPPORT Human Clinical

"Here, we present a case of a dysautonomic crisis that was resistant to the conventional treatment, treated safely and successfully with dexmedetomidine."

Establishes the off-label use in conventionally refractory crisis, and that the evidence is a single case.

Carbidopa

Action: Pharmacotherapy NCIT:C15986

Agent: carbidopa CHEBI:3395

Platform: Small molecule

A peripheral DOPA-decarboxylase inhibitor, and the best-evidenced disease-specific pharmacotherapy in this entry. Because it does not cross the blood-brain barrier it blocks catecholamine synthesis only outside the central nervous system, which is where the unrestrained release happens, and two randomized placebo-controlled crossover trials have tested it on the two halves of that problem. The 2013 antiemetic trial reduced nausea and retching (Class II evidence, mean 480 mg/day); the 2020 trial met both co-primary endpoints for blood-pressure variability at 300 and 600 mg/day (class Ib evidence). Its practical significance is that, unlike the benzodiazepines and clonidine it supplements, it causes neither sedation nor respiratory depression, so it is usable as continuous prophylaxis in patients whose chemoreflex is already failing rather than only as rescue. It is symptomatic, not disease-modifying: it lowers the catecholamine output that baroreflex failure permits and does nothing to the afferent lesion.

Mechanism Target:

INHIBITS Dysautonomic Crises — Blocking peripheral dopa-decarboxylase lowers dopamine formation outside the brain, and it is the dopamine surge that drives the retching and vomiting component of the crisis. The randomized crossover phase measured both the symptom reduction and the fall in urinary dopamine excretion, so the mechanism and the outcome were shown in the same trial.

Show evidence (2 references)

PMID:23553478 SUPPORT Human Clinical

"In the double-blind phase, patients experienced significantly less nausea and retching while on carbidopa than on placebo (p < 0.03 and p < 0.02, respectively)."

The randomized placebo-controlled crossover result on which this treatment link rests.

PMID:23553478 SUPPORT Human Clinical

"Twenty-four-hour urinary dopamine excretion was significantly lower while on carbidopa (147 ± 32 µg/gCr) than while on placebo (222 ± 41µg/gCr, p < 0.05)."

Confirms target engagement — peripheral dopamine production fell — alongside the symptom benefit, which is the mechanism this link claims.

INHIBITS Blood Pressure Instability — Suppressing peripheral catecholamine synthesis also narrows the blood-pressure swings, since the hypertensive peaks are driven by excess norepinephrine release. This is a separate trial from the antiemetic one and its endpoints were the variability itself, not the vomiting.

Show evidence (2 references)

PMID:32654554 SUPPORT Human Clinical

"The SD of systolic BP variability was reduced at both carbidopa doses (low dose: 17±4; high dose: 18±5 mm Hg) compared with placebo (23±7 mm Hg; P=0.0013), and there was a significant reduction in the systolic BP peaks on active treatment (P=0.0015)."

Both co-primary endpoints of the randomized crossover trial, measuring the effect on this node directly.

PMID:32654554 SUPPORT Human Clinical

"Twenty-four hour urinary norepinephrine excretion, a marker of peripheral catecholamine release, was significantly suppressed on both high dose and low dose carbidopa, compared with placebo (P=0.0075)."

Establishes the intervening step — suppressed peripheral catecholamine release — between the drug and the pressure effect.

Show evidence (4 references)

PMID:32654554 SUPPORT Human Clinical

"This study provides class Ib evidence that carbidopa can reduce blood pressure variability in patients with congenital afferent baroreflex failure."

The trial's own grading of its evidence level for this indication.

PMID:23553478 SUPPORT Human Clinical

"Carbidopa is a safe and effective antiemetic in patients with FD, likely by reducing the formation of dopamine outside the brain."

The antiemetic trial's conclusion, including its own hedge ("likely") on the mechanism.

PMID:25323828 SUPPORT Human Clinical

"Unlike previous treatment options, carbidopa is not associated with sedation or respiratory depression, making it suitable as a long-term pharmacotherapy to prevent"

Supports the claim that carbidopa is usable as continuous prophylaxis where the sedating alternatives are not, which is this treatment's practical advantage in a disease with chemoreflex failure.

+ 1 more reference

Midodrine for Orthostatic Hypotension

Action: Pharmacotherapy NCIT:C15986

Agent: midodrine CHEBI:6933

Platform: Small molecule

An alpha-1 adrenergic agonist that raises vascular tone, used for the hypotensive half of the blood-pressure phenotype. It is the one treatment here whose scheduling is dictated by the mechanism rather than by convenience: the pressor effect lasts only about three hours and peaks roughly an hour after an oral dose, so it is timed to activity rather than given on a fixed schedule. Supine hypertension is its characteristic adverse effect, which matters more in this disease than in most because the same patients already swing into paroxysmal hypertension and already have renal damage that pressure accelerates.

Mechanism Target:

MODULATES Blood Pressure Instability — Midodrine acts on the efferent vascular side, which the disease leaves comparatively intact, to substitute for the missing baroreflex correction of a falling pressure. It addresses only the hypotensive direction of the lability, and can push the other way, which is why the effect here is modulation rather than inhibition of the node.

Show evidence (2 references)

PMID:25323828 SUPPORT Human Clinical

"The α-1 adrenergic agonist midodrine (5–20 mg) raises blood pressure for"

States the agent's class and its pressor effect on this node.

PMID:25323828 SUPPORT Human Clinical

"Midodrine | α1-receptor agonist that increases vascular tone and, therefore, blood pressure."

The review's own pharmacology table row, naming the mechanism by which the node is affected.

Show evidence (2 references)

PMID:25323828 SUPPORT Human Clinical

"Since the peak effect is around 1 hour after oral administration, midodrine should be taken ∼45 minutes before physical activity, so that the pressor effect coincides with exercise-induced hypotension."

Supports the activity-timed rather than fixed-schedule dosing recorded in this treatment's description.

PMID:25323828 SUPPORT Human Clinical

"3-4 h. | Supine hypertension, goose bumps, increased urination."

The pharmacology table's duration and adverse-effect entries for midodrine, supporting the short duration of action and supine hypertension recorded here.

Nocturnal Non-Invasive Ventilation

Action: Non-Invasive Mechanical Ventilation NCIT:C171457

Platform: Device

Non-invasive ventilation during sleep manages apneas and prevents hypercapnia in patients whose chemoreflex cannot defend ventilation unconsciously. In the sudden-death case-control study it was the one protective factor identified, while fludrocortisone treatment was associated with markedly higher risk — so the recommendation pairs starting ventilation with stopping fludrocortisone.

Mechanism Target:

INHIBITS Sleep-Disordered Breathing — Ventilatory support substitutes for the absent chemoreflex drive during sleep, the interval in which the reflex lesion is unmasked.

Show evidence (1 reference)

PMID:25323828 SUPPORT Human Clinical

"Non-invasive ventilation during sleep effectively manages apneas and prevents hypercapnia."

States the effect of nocturnal non-invasive ventilation on the sleep-disordered breathing node.

INHIBITS Sudden Unexpected Death During Sleep — Nocturnal ventilation was protective against sudden death in the case-control study, and its initiation is the study's primary preventive recommendation.

Show evidence (1 reference)

PMID:28521050 SUPPORT Human Clinical

"Initiation of noninvasive ventilation when required and discontinuation of fludrocortisone treatment may reduce the high incidence rate of SUDS in patients with FD."

The study's own recommendation that nocturnal ventilation reduces sudden death, paired with fludrocortisone withdrawal.

Show evidence (1 reference)

PMID:28521050 SUPPORT Human Clinical

"but less likely to use noninvasive ventilation at night (OR 0.19; 0.06-0.61)"

Quantifies the protective association between nocturnal non-invasive ventilation and survival.

Feeding and Airway Management for Neurogenic Dysphagia

Action: Supportive Care NCIT:C15747

Platform: Behavioral / lifestyle

Multidisciplinary feeding teams manage the swallowing disorder, with airway protection and prompt treatment of aspiration pneumonia. This is the main lever against the respiratory cause of death and is supportive rather than disease-modifying.

Mechanism Target:

INHIBITS Neurogenic Dysphagia and Recurrent Aspiration — Feeding and airway management interrupt the step between the swallowing lesion and aspiration; they do not touch the neuronal deficit that causes the dysphagia.

Show evidence (1 reference)

PMID:25323828 SUPPORT Human Clinical

"Managing neurogenic dysphagia with effective protection of the airway passages and prompt treatment of aspiration pneumonias is necessary to prevent respiratory failure."

Identifies airway protection and dysphagia management as the intervention on this node.

Show evidence (1 reference)

PMID:20301359 SUPPORT Human Clinical

"Feeding teams manage neurogenic dysphagia; mental health professionals treat anxiety."

Documents the multidisciplinary feeding-team model of care.

Percutaneous Endoscopic Gastrostomy

Action: Percutaneous Endoscopic Gastrostomy NCIT:C106040

Platform: Surgery

Gastrostomy placement is the standard answer to the feeding side of the swallowing lesion, used when feeding aversion and failure to thrive are not manageable with thickened formula and nasogastric feeding. It bypasses the unprotected oropharyngeal swallow rather than correcting it, which is what makes it a durable answer in a disease where neurogenic dysphagia persists for life. It also becomes the route for medication and fluids, and that creates a hazard specific to this disease: patients do not regulate water intake by thirst, so free water given through the tube can produce water intoxication.

Mechanism Target:

BYPASSES Neurogenic Dysphagia and Recurrent Aspiration — Enteral feeding delivers calories without passing a bolus through the incoordinate, unprotected swallow, so it removes the oral route by which aspiration occurs rather than restoring swallowing function.

Show evidence (1 reference)

PMID:25323828 SUPPORT Human Clinical

"Feeding aversion and failure to thrive are managed with percutaneous endoscopic gastrostomy (PEG) placement"

Establishes gastrostomy placement as the management of the feeding consequences of this node.

Show evidence (3 references)

PMID:25323828 SUPPORT Human Clinical

"Thickened formula and nasograstric feeding may be required to manage caloric intake in infants."

Documents the less invasive measures that precede gastrostomy in the same management sequence.

PMID:25323828 SUPPORT Human Clinical

"Neurogenic dysphagia persists throughout life, and eating by mouth can become a challenge."

Supports the claim that the swallowing lesion is lifelong, which is why the enteral route is durable rather than temporary.

PMID:25323828 SUPPORT Human Clinical

"they should be cautioned to avoid excessive free water intake through the gastrostomy tube to avoid water intoxication."

Documents the disease-specific hazard the gastrostomy route introduces, recorded in this treatment's description.

Fundoplication

Action: Fundoplication NCIT:C91834

Platform: Surgery

An antireflux wrap, performed in 72% of patients in the US, addressing the gastroesophageal reflux that occurs in about three quarters of them and adds a second route to aspiration on top of the swallowing lesion. It is included here with its own evidence of limits rather than as a settled benefit: the review states that its effect on natural history compared with untreated patients is unclear, that reflux can recur, that up to 12% need a second operation, and that oesophageal dilatation and achalasia are increasingly recognized afterwards. One independent corroboration of the wrap's mechanical effect comes from the carbidopa antiemetic trial, where every enrolled patient had had a fundoplication and none could vomit — they retched instead, which is why that trial's endpoints were nausea and retching rather than vomiting.

Mechanism Target:

INHIBITS Gastrointestinal Dysmotility — The wrap acts on the gastroesophageal reflux component of the dysmotility phenotype, mechanically opposing retrograde flow. It does not touch the enteric neuronal lesion that produces the dysmotility, and the same denervated oesophagus is why dilatation and achalasia follow the procedure more often here than in an otherwise normal gut.

Show evidence (2 references)

PMID:25323828 SUPPORT Human Clinical

"Gastroesophageal reflux occurs in 75% of FD patients."

Quantifies the reflux component of this node that the procedure is aimed at.

PMID:25323828 REFUTE Human Clinical

"Esophageal dilatation and achalasia (i.e., abnormal esophageal peristalsis) are increasingly recognized complications after fundoplication surgery."

Cuts against the claim that the procedure inhibits this node overall, since two of its recognized complications are themselves oesophageal dysmotility.

Show evidence (4 references)

PMID:25323828 SUPPORT Human Clinical

"fundoplication surgery has been performed in 72% of patients with FD in the US"

Establishes how widely the procedure is used in this population.

PMID:23553478 SUPPORT Human Clinical

"Previous fundoplication surgery in each patient studied prevented vomiting"

Independent observation, from a trial cohort in which every patient had had the procedure, that the wrap mechanically prevents vomiting — and the reason that trial measured retching instead.

PMID:25323828 REFUTE Human Clinical

"The impact of the fundoplication wrap on the natural history of these patients compared with that of untreated patients is still unclear."

The review declines to credit the procedure with a change in natural history, which is evidence against treating it as an established benefit.

+ 1 more reference

Ocular Surface Lubrication

Action: Pharmacotherapy NCIT:C15986

Agent: carboxymethylcellulose CHEBI:85146

Platform: Small molecule

Maintaining corneal moisture is the preventive treatment for the corneal limb of the eye disease, and it is the only ophthalmic intervention here that acts before damage rather than after it. The regimen is defined by frequency rather than by a single agent — preservative-free artificial tears every two to three hours, liquid gels every four to six, and a carboxymethylcellulose, glycerin, mineral-oil or petrolatum ointment overnight — because alacrima removes tear production continuously rather than episodically. It does nothing for the retinal ganglion cell optic neuropathy, which is a separate cause of visual loss in this entry.

Mechanism Target:

INHIBITS Corneal Opacity and Neurotrophic Keratopathy — Topical lubrication substitutes for the missing tear film, which is one of the two upstream causes of the corneal damage. It does not restore corneal sensation, so the hypoesthesia arm of the lesion is untouched — which is why the treatment is preventive of surface breakdown rather than curative.

Show evidence (1 reference)

PMID:25323828 SUPPORT Human Clinical

"Therapeutic approaches focus on maintaining corneal moisture to avoid dry eye complications, including recurrent corneal abrasions, ulcers, and permanent opacities."

States the therapeutic aim and names the corneal outcomes it is intended to prevent, which are this node's content.

Show evidence (1 reference)

PMID:25323828 SUPPORT Human Clinical

"Treatments include preservative-free artificial tears (every 2-3 hours), liquid gels (every 4-6 hours), and ointments (e.g., carboxymethyl cellulose, glycerin, mineral oil, or white petrolatum at bedtime or every 8-12 hours)."

Enumerates the preparations and dosing frequencies recorded in this treatment's description, including the carboxymethylcellulose bound as the therapeutic agent.

Splice-Modulating Therapy (Kinetin and Derivatives)

Action: Pharmacotherapy NCIT:C15986

Agent: kinetin CHEBI:27407

Platform: Small molecule

Investigational, and the only approach that targets the molecular defect. Kinetin shifts ELP1 splicing toward the full-length transcript. In an open 28-day study of eight homozygous patients it raised wild-type ELP1 message in leukocytes with no dose escalation, establishing target engagement in humans but not clinical benefit. Benefit has been shown only in the humanized mouse. No splice-modulating agent is approved for this disease.

Mechanism Target:

INHIBITS Tissue-Specific Skipping of ELP1 Exon 20 — Kinetin acts on the splicing step itself, increasing the fraction of transcripts that retain exon 20 — the only node in this entry's chain upstream of the neuronal loss that a drug can currently reach.

Show evidence (1 reference)

PMID:21775922 SUPPORT Human Clinical

"An increase in WT IKBKAP mRNA expression in leukocytes was noted after 8 d in six of eight individuals; after 28 d, the mean increase compared with baseline was significant (p = 0.002)."

Demonstrates that kinetin shifts ELP1 splicing in patients, the mechanism this link claims.

Show evidence (2 references)

PMID:21775922 SUPPORT Human Clinical

"This is the first report of a drug that produces in vivo mRNA splicing changes in individuals with FD and supports future long-term trials to determine whether kinetin will prove therapeutic in FD patients."

Establishes target engagement in humans while stating explicitly that therapeutic benefit remains to be determined.

PMID:25323828 SUPPORT Human Clinical

"Clinical trials of compounds that increase levels of IKAP (ELP-1) are underway and will determine whether they can reverse or slow disease progression."

Confirms that disease-modifying efficacy was still an open question at the time of this review.

Phosphatidylserine

Action: Pharmacotherapy NCIT:C15986

Agent: phosphatidylserine CHEBI:18303

Platform: Small molecule

Investigational, and worth modelling separately from kinetin because its mechanism is different rather than merely its chemistry: kinetin shifts the exon 20 inclusion-to-skipping ratio, whereas phosphatidylserine raises ELP1 transcription without altering that ratio. Both therefore converge on the same target — more ELP1 protein in neurons — by non-overlapping routes, which is the stated reason the two might be combined. Human evidence is early: a small number of patients showed an ELP1 rise with acceptable tolerability, and whether that translates into rescue or delay of optic atrophy and gait ataxia was still the object of ongoing long-term trials at the time of this review. Nothing here is a clinical outcome.

Mechanism Target:

RESTORES Neuronal Elongator Complex Deficiency — Because it raises ELP1 transcription rather than correcting the splice ratio, phosphatidylserine acts on the protein-level deficit itself, one node downstream of where kinetin acts. This is the reason it is linked here and not to the exon 20 skipping node: the mis-splicing is unchanged.

Show evidence (2 references)

PMID:25323828 SUPPORT Human Clinical

"While kinetin increases the levels of correctly spliced IKAP transcripts, thus altering the ratio between exon 20 inclusion and skipping, phosphatidylserine appears to increase levels of transcription without altering the ratio."

States the mechanistic distinction that places this treatment on the Elongator-deficiency node rather than on the splicing node.

PMID:25323828 SUPPORT Human Clinical

"Initial studies of phosphatidylserine in a small number of FD patients have demonstrated an increase in IKAP (ELP-1) levels and have shown that it is safe and well tolerated."

The human target-engagement result — an ELP1 rise in patients — on which this link rests, with the review's own note that the sample was small.

Show evidence (2 references)

PMID:25323828 SUPPORT In Vitro

"Phosphatidylserine, a phospholipidic component of cell membranes, has been shown to raise IKAP (ELP-1) levels in cell lines and animal models of FD."

The preclinical basis for the agent. Graded IN_VITRO for the cell-line result the sentence reports; the same sentence also cites animal models, which is why the human evidence above is quoted separately rather than folded into this item.

PMID:25323828 SUPPORT Human Clinical

"Long-term trials are underway to determine whether raising IKAP (ELP-1) levels can rescue or delay the progressive worsening of neurological features like optic atrophy and gait ataxia."

Establishes that clinical benefit was unresolved and under test, which is why this treatment is recorded as investigational.

Genetic Counseling and Carrier Screening

Action: Genetic Counseling NCIT:C15240

Counselling for autosomal recessive inheritance, with population-based carrier screening offered to people of Ashkenazi Jewish heritage. Screening has had an unusually large effect for a genetic service: it has almost eliminated new births with the disorder.

Show evidence (2 references)

PMID:20301359 SUPPORT Human Clinical

"Carrier screening is available on a population basis for individuals of Ashkenazi Jewish heritage."

Documents population-based carrier screening in the at-risk population.

PMID:29290691 SUPPORT Human Clinical

"Genetic testing programs, which were established shortly after the disease-causing mutations were identified, have almost completely eliminated the birth of children with this disorder."

Quantifies the effect of the screening programs on disease incidence.

🌍

Environmental Factors

2

Hot or humid weather

Bound to the heat half only. ECTO has no humidity-exposure class: searched the pinned local build with `runoak -i sqlite:obo:ecto info` for `l~humid` (returns ENVO:01000828 humid air, ENVO:09200015 humidity of soil, PATO:0015009 humidity, PATO:0015010 increased humidity — all qualities or material entities, none an exposure event and none in the ExposureTerm enum), `l~humidity` (no ECTO terms), `l~moist` (no ECTO terms), and `l~weather` (only ECTO:1000020 exposure to weather, which is broader than the heat term and loses the temperature claim). XCO has only XCO:0000993 controlled humidity, a laboratory-controlled condition rather than ambient humid weather. ECTO:1000007 was preferred over ECTO:1000018 exposure to extreme high temperature environment because the source says "hot", not extreme, and over ECTO:4000001 exposure to increased temperature because the claim is about the ambient environment rather than a temperature increase in an unspecified medium. The humidity sense is carried by preferred_term.

GeneReviews lists hot or humid weather among the circumstances to avoid because it exacerbates symptoms. The mechanism is not stated there, but it coheres with the rest of this entry: autonomic thermoregulation is defective — difficulty regulating body temperature is among the disease's listed features — so an ambient heat load is one the patient cannot compensate for, and the compensatory demand falls on the same sympathetic outflow that has no baroreflex restraining it. Recorded here as an exacerbating exposure rather than a trigger of the disease.

Show evidence (2 references)

PMID:20301359 SUPPORT Human Clinical

"The following can exacerbate symptoms: hot or humid weather; full bladder."

The GeneReviews avoid-list entry establishing this exposure as symptom-exacerbating.

PMID:30905397 SUPPORT BACKGROUND Human Clinical

"Individuals with FD have decreased sensitivity to pain and temperature sensation, visual loss, kyphoscoliosis, proprioceptive ataxia, and difficulties in regulating body temperature."

Supports the thermoregulatory-failure rationale in this entry's description by establishing that patients have difficulty regulating body temperature. It does not itself state that heat exacerbates symptoms.

Mechanism Target:

EXACERBATES Dysautonomic Crises — Heat exposure worsens symptoms in a patient who cannot thermoregulate autonomically. The steps between the ambient load and a hyperadrenergic crisis are not established in the cited source, which states the exacerbation without a mechanism, so the edge is typed as having unknown intermediates.

Show evidence (1 reference)

PMID:20301359 SUPPORT Human Clinical

"The following can exacerbate symptoms: hot or humid weather; full bladder."

GeneReviews names hot or humid weather as a symptom-exacerbating circumstance to avoid.

Full bladder

Left unbound: neither ECTO nor XCO has a bladder-distension or visceral-stimulus exposure class. Searched the pinned local builds with `runoak -i sqlite:obo:ecto info` for `l~bladder`, `l~distension`, `l~distention`, `l~visceral`, `l~stretch` and `l~retention` (no ECTO terms for any of the six) and `l~urine` (returns only ECTO:9000202 exposure to purines and an unrelated enzyme-inhibitor term). `runoak -i sqlite:obo:xco info` for `l~distension`, `l~distention`, `l~full ` and `l~visceral` returns no XCO terms; `l~bladder` returns only XCO:0001279 partial bladder outlet obstruction, which is an outflow obstruction rather than a distended bladder, and `l~urin` returns XCO:0001101 urinary catheterization, which is the intervention that relieves this exposure rather than the exposure. No term beats a wrong one, so the concept is carried in preferred_term alone.

GeneReviews lists a full bladder among the circumstances to avoid because it exacerbates symptoms. It belongs to the same class of visceral-afferent stimulus that provokes hyperadrenergic episodes in other afferent-lesioned autonomic disorders, and it is a modifiable one — which is why it appears on an avoid list rather than only in a mechanism discussion. The cited source states the exacerbation without a mechanism and this entry does not supply one.

Show evidence (1 reference)

PMID:20301359 SUPPORT Human Clinical

"The following can exacerbate symptoms: hot or humid weather; full bladder."

The GeneReviews avoid-list entry establishing this exposure as symptom-exacerbating.

Mechanism Target:

EXACERBATES Dysautonomic Crises — A distended bladder is an avoidable precipitant of symptom exacerbation. The cited source lists it without a mechanism, so no intermediate steps are asserted here.

Show evidence (1 reference)

PMID:20301359 SUPPORT Human Clinical

"The following can exacerbate symptoms: hot or humid weather; full bladder."

GeneReviews names a full bladder as a symptom-exacerbating circumstance to avoid.

🔬

Diagnosis

4

Molecular genetic testing of ELP1

The diagnosis is established by finding biallelic pathogenic ELP1 variants. Because one founder allele accounts for essentially all cases, targeted testing for IVS20+6T>C is usually sufficient, but the P914L report means ancestry is no longer a precondition for testing.

Show evidence (1 reference)

PMID:20301359 SUPPORT Human Clinical

"The diagnosis of familial dysautonomia is established in a proband with suggestive findings and biallelic pathogenic variants in ELP1 (formerly IKBKAP) identified by molecular genetic testing."

States the molecular diagnostic standard.

Inspection of the tongue for fungiform papillae

A bedside examination usable in a newborn. The papillae are absent in essentially every patient, so a smooth tongue in an infant with alacrima and feeding difficulty is a strong pointer to the diagnosis.

Show evidence (1 reference)

PMID:14245781 SUPPORT Human Clinical

"Inspection of the tongue may thus be useful for diagnosing this rare disease, even in infants."

Establishes tongue inspection as a diagnostic manoeuvre usable in infancy.

Optical coherence tomography of the retina and optic nerve head

Spectral-domain OCT measurement of retinal nerve fibre layer and macular ganglion cell and inner plexiform layer thickness tracks the optic neuropathy quantitatively. It was developed for this disease specifically because there was no useful biomarker for clinical monitoring.

Show evidence (2 references)

PMID:33180192 SUPPORT Human Clinical

"Familial Dysautonomia (FD) disease, lacks a useful biomarker for clinical monitoring."

States the monitoring gap this imaging study set out to fill.

PMID:33180192 SUPPORT Human Clinical

"All subjects were imaged with spectral-domain Optical Coherence Tomography (OCT). Global and sectoral measurements of mean retinal nerve fiber layer (RNFL) and macular ganglion cell and inner plexiform layer (GCIPL) thickness"

Describes the imaging modality and the measures used.

Polysomnography

Sleep studies identify the obstructive and central events that drive the risk of sudden death during sleep, and are the basis for deciding who needs nocturnal non-invasive ventilation. GeneReviews places sleep-disordered breathing under routine lifelong surveillance.

Show evidence (2 references)

PMID:20301359 SUPPORT Human Clinical

"pulmonary function, sleep-disordered breathing, frequency and severity of dysautonomic crises"

Lists sleep-disordered breathing among the parameters under routine surveillance.

PMID:28521050 SUPPORT Human Clinical

"We retrospectively identified patients with FD who died suddenly and unexpectedly during sleep and had undergone polysomnography within the 18-month period before death."

Establishes polysomnography as the study used to stratify sudden-death risk in this population.

📈

Progression

3

Congenital

The disease is expressed at birth. Absent fungiform papillae, alacrima, hypotonia, blunted temperature sensation and feeding difficulty are present from infancy, reflecting the developmental component of the neuronal lesion.

Show evidence (1 reference)

PMID:37204536 SUPPORT Human Clinical

"Familial dysautonomia (FD) is an autosomal recessive hereditary sensory and autonomic neuropathy (HSAN, type 3) expressed at birth with profound sensory loss and early death."

States that the disease is expressed at birth with profound sensory loss.

Progressive neurodegeneration

Neuronal degeneration continues throughout life. Pain sensation worsens, proprioceptive ataxia deepens toward loss of independent ambulation, and retinal nerve fibre layer thinning progresses until it plateaus in the mid-twenties, by which time visual loss is often at the level of legal blindness.

Show evidence (2 references)

PMID:20301359 SUPPORT Human Clinical

"Neuronal degeneration progresses throughout life."

States the lifelong progressive course.

PMID:37204536 SUPPORT Human Clinical

"Progressive features of the disease include retinal nerve fiber loss and blindness, and proprioceptive ataxia with severe gait impairment."

Names the specific features that progress.

Adult survival

Survival has improved with supportive care but remains reduced: about half of patients reach 40 years of age. The leading causes of death are sudden unexpected death during sleep, aspiration pneumonia, and respiratory insufficiency.

Show evidence (2 references)

PMID:26769677 SUPPORT BACKGROUND Human Clinical

"Despite advances in patient care, the disorder is inevitably fatal, with only 50% of patients reaching 40 years of age"

Quantifies survival to age 40.

PMID:30905397 SUPPORT BACKGROUND Human Clinical

"Unexplained sudden death, aspiration pneumonias, and respiratory insufficiency remain the leading causes of death."

Names the leading causes of death.

📊

Prevalence

3

Ashkenazi Jewish population

Carrier Frequency 3125.0 per 100,000 >1 in 1,000 (carriers)

Measured carrier frequency 1 in 32 among 1100 full Ashkenazi Jewish individuals screened in Israel (34 carriers), converted to 3125 per 100,000.

Show evidence (1 reference)

PMID:12885336 SUPPORT Human Clinical

"Among the 1100 full AJ tested, 34 were found to be FD carriers (1:32)."

Direct measurement of the carrier frequency in the general Ashkenazi Jewish population.

Ashkenazi Jews of Polish descent

Carrier Frequency 5555.0 per 100,000 >1 in 1,000 (carriers)

1 in 18 among Ashkenazi Jews of Polish descent versus 1 in 99 among non-Polish Ashkenazi Jews, converted to 5555 per 100,000. The subpopulation difference is consistent with the founder allele's origin in the Pale of Settlement.

Show evidence (1 reference)

PMID:12885336 SUPPORT Human Clinical

"The incidence of mutation carriers was significantly higher in AJ of Polish descent (1:18) compared to AJ of non-Polish descent (1:99)."

Establishes the higher carrier rate in the Polish Ashkenazi subpopulation.

Worldwide

Cases In Literature Ultra Rare

No more than about 700 patients have been identified worldwide. Carrier screening has since almost eliminated new births, so the affected population is not expected to grow.

Show evidence (2 references)

PMID:30890343 SUPPORT Human Clinical

"Although a rare disease with no more than 700 identified cases"

Gives the total number of identified cases worldwide.

PMID:29290691 SUPPORT Human Clinical

"Genetic testing programs, which were established shortly after the disease-causing mutations were identified, have almost completely eliminated the birth of children with this disorder."

Supports the claim that carrier screening has nearly stopped new births.

🔀

Differential Diagnoses

1

Conditions with similar clinical presentations that must be differentiated from Riley-Day Syndrome:

Other hereditary sensory and autonomic neuropathies

Overlapping Features Familial dysautonomia is type III of the numbered HSAN series, whose members share impaired pain and temperature sensation but differ in gene, inheritance, and the balance of sensory against autonomic involvement. HSAN IV (NTRK1, congenital insensitivity to pain with anhidrosis) is the closest clinical mimic in an infant, since it also presents with insensitivity to pain and autonomic signs. The distinguishing features here are the absent fungiform papillae, alacrima, and afferent baroreflex failure, and the diagnosis is settled molecularly.

Show evidence (2 references)

PMID:37204536 SUPPORT Human Clinical

"Familial dysautonomia (FD) is an autosomal recessive hereditary sensory and autonomic neuropathy (HSAN, type 3)"

Places this disease as one type within the HSAN series from which it must be distinguished.

PMID:20301359 SUPPORT Human Clinical

"The diagnosis of familial dysautonomia is established in a proband with suggestive findings and biallelic pathogenic variants in ELP1 (formerly IKBKAP) identified by molecular genetic testing."

Supports the claim that the differential within the HSAN series is settled by molecular testing.

🔬

Clinical Trials

1

NCT06148311 PHASE_II ENROLLING_BY_INVITATION

Placebo-controlled study of a sublingual dexmedetomidine film for aborting hyperadrenergic autonomic crisis outside hospital. It matters for this entry because the existing dexmedetomidine evidence is a single intravenous case, which confines the drug to inpatient use; a sublingual film would move an alpha-2 agonist into the ambulatory setting where crises actually start. The registered aims are feasibility plus whether heart rate, blood pressure and oxygen saturation can predict crisis onset, so a positive result would also give this disease a prodromal signal it currently lacks.

Target Phenotypes: Episodic hypertension (dysautonomic crisis) HP:0000875

Show evidence (2 references)

clinicaltrials:NCT06148311 SUPPORT Human Clinical

"The purpose of this placebo controlled interventional study is to collect preliminary data on administering dexmedetomidine in patients with Familial Dysautonomia (FD) during a rapid cessation of autonomic crisis."

The registry's own statement of the trial's design and indication, establishing that it tests dexmedetomidine against dysautonomic crisis in this disease.

clinicaltrials:NCT06148311 SUPPORT Human Clinical

"The primary aims are to assess the feasibility and evaluate if measurements of heart rate, blood pressure and oxygen saturation can predict the start of an autonomic crisis."

Establishes the primary aims recorded in this trial's description, including the crisis-prediction objective.

🐁

Animal Models

1

TgFD9;Elp1 humanized familial dysautonomia mouse

The complete human ELP1 (IKBKAP) gene carrying the founder splice mutation was introduced as a transgene into a mouse expressing very little endogenous Elp1. Unlike earlier knockout attempts, this reproduces the human molecular defect itself — tissue-specific mis-splicing of a human transgene — rather than simply lowering Elp1, which is what makes it usable for testing splice-modulating drugs.

Species

Mouse

Genotype

TgFD9 human ELP1 transgene carrying IVS20+6T>C, on an Elp1 delta20/flox background

Publication

PMID:26769677

Pathograph links

Tissue-Specific Skipping of ELP1 Exon 20 recapitulates fidelity: high observes: molecular The transgene reproduces the same tissue-specific exon 20 mis-splicing seen in patients, which is the property the model was built for.

Show evidence (1 reference)

PMID:26769677 SUPPORT Model Organism

"recreates the same tissue-specific mis-splicing defect seen in FD patients"

States that the model reproduces the human mis-splicing defect.

Failed Development and Innervation of Sensory and Autonomic Neurons recapitulates fidelity: moderate observes: cellular The mouse shows sensory and sympathetic impairment and a reduced number of fungiform papillae, the developmental readouts of this node.

Limitations: Mouse Ikap is only about 80% identical to human IKAP, and the phenotype is produced by a human transgene on a hypomorphic mouse background rather than by the endogenous locus, so absolute expression levels are not those of a patient.

Show evidence (1 reference)

PMID:26769677 SUPPORT Model Organism

"recapitulates many phenotypic features of the human disease, including reduced growth rate, reduced number of fungiform papillae, spinal abnormalities, and sensory and sympathetic impairments"

Establishes the model as informative for the sensory and autonomic developmental phenotype.

Postnatal Proprioceptive Neuron Loss recapitulates fidelity: high observes: tissue The model reproduces the proprioceptive impairment seen in patients, and postnatal kinetin prevents the proprioceptive neuron loss and the spinal abnormalities that follow it — a rescue experiment that is also the strongest available evidence for the causal direction of this node.

Readouts

Onset of spinal abnormalities under postnatal kinetin

Direction: RESTORED

Interpretation: Preventing proprioceptive neuron loss prevents the spinal deformity, supporting the proprioception-to-kyphoscoliosis edge in this entry.

Show evidence (1 reference)

PMID:30905397 SUPPORT Model Organism

"Daily administration of kinetin starting at birth improves sensory-motor coordination and prevents the onset of spinal abnormalities by stopping the loss of proprioceptive neurons."

Reports the measured rescue of proprioceptive neuron loss and of the spinal phenotype.

Show evidence (1 reference)

PMID:30905397 SUPPORT Model Organism

"We demonstrate herein that the FD mouse TgFD9;IkbkapΔ20/flox recapitulates the proprioceptive impairment observed in individuals with FD"

Establishes the model as informative for the proprioceptive node.

Retinal Ganglion Cell Degeneration recapitulates fidelity: moderate observes: tissue The same mouse develops a progressive retinal phenotype, which was characterized specifically to support development of therapies for the optic neuropathy.

Limitations: The murine retina lacks a macula, so the model cannot reproduce the macular ganglion cell and inner plexiform layer thinning that is the main quantitative measure of progression in patients.

Show evidence (1 reference)

PMID:34908112 SUPPORT Model Organism

"we comprehensively characterized the progression of the retinal phenotype in this mouse, and we demonstrated that it is possible to correct ELP1 splicing defect in the retina using the splicing modulator compound (SMC) BPN-15477."

Establishes the retinal phenotype in this model and its correctability by a splicing modulator.

Show evidence (2 references)

PMID:26769677 SUPPORT Model Organism

"This new mouse model, TgFD9; Ikbkap(Δ20/flox) was created by introducing the complete human IKBKAP transgene with the major FD splice mutation (TgFD9) into a mouse that expresses extremely low levels of endogenous Ikbkap"

Describes the construction of the model, establishing that it carries the human founder allele.

PMID:36809767 SUPPORT Model Organism

"Remarkably, PTC258 treatment improves survival, gait ataxia, and retinal degeneration in the phenotypic FD mice."

Shows the model responds to a brain-penetrant splicing modulator across survival, gait and retinal endpoints.

{ }

Source YAML

click to show

name: Riley-Day Syndrome
creation_date: "2026-09-21T00:00:00Z"
category: Mendelian
description: >-
  Riley-Day syndrome, more usually called familial dysautonomia (FD), is
  hereditary sensory and autonomic neuropathy type III: an autosomal recessive
  disorder in which sensory, sympathetic, and parasympathetic neurons fail to
  develop in normal numbers and then degenerate progressively through life. It
  is caused almost entirely by one Ashkenazi Jewish founder allele, a T-to-C
  transition at position +6 of the ELP1 (formerly IKBKAP) intron 20 donor splice
  site. The change weakens rather than abolishes the splice site, so exon 20 is
  skipped only partially and the resulting ELP1 deficit is tissue-specific,
  deepest in the central and peripheral nervous system and mildest in
  non-neuronal tissue. ELP1 is the scaffolding subunit of the six-subunit
  Elongator complex, which acts in transcriptional elongation, alpha-tubulin
  acetylation, and tRNA wobble-uridine modification, and which neurons need for
  development, target innervation, and survival.

  The clinical picture follows from which neuronal populations are lost. Absent
  fungiform papillae, alacrima, and blunted pain and temperature sensation are
  present from birth and reflect a developmental failure of nociceptive and
  autonomic neurons. Loss of the afferent limb of the baroreflex and chemoreflex
  produces the disorder's two most dangerous features: hyperadrenergic
  "dysautonomic crises" of hypertension, tachycardia, and intractable vomiting,
  and an absent ventilatory response to hypoxia that underlies sudden
  unexpected death during sleep. Other features are progressive rather than
  congenital — proprioceptive neurons and retinal ganglion cells are born
  normally and die postnatally, producing gait ataxia, kyphoscoliosis, and an
  optic neuropathy that often reaches legal blindness in the third decade.
  Neurogenic dysphagia causes recurrent aspiration and chronic lung disease.

  That the founder allele is leaky is also what makes the disease druggable:
  raising the fraction of correctly spliced ELP1 should help, and does. Kinetin
  shifts splicing in patients' leukocytes and rescues proprioceptive and spinal
  phenotypes in the humanized TgFD9 mouse; optimized, brain-penetrant kinetin
  derivatives rescue gait ataxia and retinal degeneration in the same model. No
  disease-modifying therapy is yet established in humans, so current care
  remains symptomatic and preventive.
disease_term:
  preferred_term: Riley-Day syndrome (familial dysautonomia, HSAN III)
  term:
    id: MONDO:0009131
    label: Riley-Day syndrome
parents:
- Hereditary Sensory and Autonomic Neuropathy
- Peripheral Neuropathy
- hereditary disease
references:
- reference: PMID:20301359
  title: "Familial Dysautonomia."
  tags:
  - GeneReviews
  findings: []
- reference: PMID:11179021
  title: "Familial dysautonomia is caused by mutations of the IKAP gene."
  findings: []
- reference: PMID:37204536
  title: "Familial dysautonomia."
  findings: []
notes: >-
  Absence of fungiform papillae is a cardinal, near-pathognomonic sign of this
  disease, but HPO has no term for it. Searched the HPO via OLS for "fungiform
  papillae" (returns only HP:0031042 Strawberry tongue), "lingual papilla"
  (HP:0010298 Smooth tongue, HP:0025252 Geographic tongue), "tongue papillae"
  (the same two plus HP:0031042), "papilla" (thyroid, papillary-muscle, and
  conjunctival terms only), and "taste" (HP:0041051 Ageusia, HP:0000224
  Hypogeusia and other taste-quality terms, none about receptor structures).
  HP:0010298 Smooth tongue is the near miss and is the wrong concept: its HPO
  definition is "This is due to reduction in number and/or size of the filiform
  papillae", and filiform papillae are the non-gustatory ones, which are not
  what is missing here. The phenotype is therefore bound to the parent term
  HP:0030809 Abnormal tongue morphology with the specificity carried in
  preferred_term.

  The neuron-loss node is bound to GO:0008219 cell death, not to a neuron-death
  term, because GO has retired that whole branch. A review asked for
  GO:0051402 neuron apoptotic process to be replaced by GO:0070997 neuron death,
  on the correct ground that no cited evidence here establishes apoptosis
  specifically — the human data are autopsy neuron counts. But GO:0070997's
  canonical label is "obsolete neuron death", and `runoak -i sqlite:obo:go info
  'l~neuron death'` returns eleven terms of which all eleven are obsolete,
  including GO:1901214-GO:1901216 and the oxidative-stress variants; `runoak -i
  ols:go search "neuron death"` returns only GO:0051402 and its three regulation
  children. So GO offers no non-obsolete term for neuron death that does not
  commit to apoptosis, and the choice is between a term asserting a death mode
  the evidence does not establish and a broader term that asserts none.
  GO:0008219 is the latter, is non-obsolete, is in the biologicalprocessterm
  enum cache, and is already used across the KB; the neuron specificity is
  carried by preferred_term, which is what the Ontology Term Contract provides
  for.

  Two carbidopa trials are cited by PMID but not recorded in clinical_trials.
  ClinicalTrials.gov has NCT01212484 (Carbidopa for the Treatment of Nausea and
  Vomiting in Familial Dysautonomia) and NCT02553265 (Carbidopa for the
  Treatment of Excessive Blood Pressure Variability), which plainly correspond
  to PMID:23553478 and PMID:32654554 by subject. Neither registration declares
  either paper as its results publication — NCT02553265 lists PMID:23553478 only
  under BACKGROUND, and NCT01212484 lists no references at all — so pairing them
  would be an inference the registry does not make. They are omitted rather than
  asserted. NCT06148311 is recorded because its identity, phase and status were
  each read directly from the registry.
pathophysiology:
- name: ELP1 Intron 20 Donor Splice Site Weakening
  biological_scale: MOLECULAR
  description: >-
    The Ashkenazi founder allele is a T-to-C transition at the sixth base of
    ELP1 intron 20, in the donor (5') splice site of exon 20. It weakens the
    site without inactivating it, so it is a hypomorphic rather than a null
    allele — patient cells still make some correctly spliced transcript, which
    is why a recessive, uniformly homozygous disease nonetheless varies in
    severity and is a candidate for splice-modulating therapy. A minority of
    alleles are instead missense changes (R696P in exon 19, and P914L in exon
    26, the first non-Jewish allele found).
  genes:
  - preferred_term: ELP1 (formerly IKBKAP)
    term:
      id: hgnc:5959
      label: ELP1
  biological_processes:
  - preferred_term: mRNA 5'-splice site recognition at ELP1 exon 20
    term:
      id: GO:0000395
      label: mRNA 5'-splice site recognition
    modifier: DECREASED
  downstream:
  - target: Tissue-Specific Skipping of ELP1 Exon 20
    causal_link_type: DIRECT
    description: >-
      A weakened donor site is recognized by the spliceosome only some of the
      time, so exon 20 is skipped in a variable fraction of transcripts.
    evidence:
    - reference: PMID:11179021
      reference_title: "Familial dysautonomia is caused by mutations of the IKAP gene."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "the RNA encoding the IkappaB kinase complex-associated protein (IKAP) lacks exon 20 and, as a result of a frameshift, encodes a truncated protein. Sequence analysis reveals a T-->C transition in the donor splice site of intron 20."
      explanation: Links the intron 20 donor-site transition directly to loss of exon 20 from the mature transcript.
  evidence:
  - reference: PMID:11179021
    reference_title: "Familial dysautonomia is caused by mutations of the IKAP gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These findings demonstrate that mutations in the gene encoding IKAP are responsible for FD."
    explanation: Establishes ELP1 (IKAP) mutation as the cause of familial dysautonomia.
  - reference: PMID:12687659
    reference_title: "Identification of the first non-Jewish mutation in familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Interestingly, despite the fact that FD is a recessive disease, normal mRNA and protein are expressed in patient cells."
    explanation: Documents that the founder allele is leaky — patient cells retain some correctly spliced product — which is the premise of splice-modulating therapy.
- name: Tissue-Specific Skipping of ELP1 Exon 20
  biological_scale: MOLECULAR
  description: >-
    Exon 20 skipping produces a frameshifted, truncated transcript. Crucially
    the skipping fraction differs by tissue: the nervous system produces mostly
    mutant transcript while fibroblasts and other non-neuronal tissue produce
    close to equal amounts of wild-type and mutant message. This tissue
    selectivity, not the mutation's severity, is what makes an otherwise
    ubiquitously expressed housekeeping gene cause a purely neurological
    disease.
  genes:
  - preferred_term: ELP1 (formerly IKBKAP)
    term:
      id: hgnc:5959
      label: ELP1
  downstream:
  - target: Neuronal Elongator Complex Deficiency
    causal_link_type: DIRECT
    description: >-
      Because the skipped transcript is frameshifted and non-functional, the
      nervous system's high skipping fraction translates into a low neuronal
      concentration of ELP1 protein and therefore of assembled Elongator.
    evidence:
    - reference: PMID:37204536
      reference_title: "Familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The mutation yield a tissue-specific skipping of exon 20 and a loss of function of the elongator-1 protein (ELP1), which is essential for the development and survival of neurons."
      explanation: States the step from exon 20 skipping to ELP1 loss of function in neurons.
  evidence:
  - reference: PMID:26769677
    reference_title: "Sensory and autonomic deficits in a new humanized mouse model of familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "the relative amount of MU and WT IKBKAP transcripts varies between tissues, with the lowest levels of WT IKBKAP mRNA and IKAP protein in tissues from the central and peripheral nervous system"
    explanation: Establishes the tissue gradient of mis-splicing — lowest wild-type message in nervous tissue — quoted from this mouse paper's account of the human molecular defect.
  - reference: PMID:21775922
    reference_title: "Kinetin improves IKBKAP mRNA splicing in patients with familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "the splicing abnormality primarily affects neuronal tissue, which produces mostly the shortened or mutant IKBKAP mRNA and a minimal amount of functional protein product"
    explanation: Independently states that mis-splicing is concentrated in neuronal tissue, leaving it with minimal functional protein.
- name: Neuronal Elongator Complex Deficiency
  biological_scale: MOLECULAR
  description: >-
    ELP1 is the scaffolding subunit of the six-subunit Elongator complex. Its
    depletion in neurons compromises the complex's known activities —
    transcriptional elongation, acetylation of cytoskeletal alpha-tubulin, and
    tRNA wobble-uridine modification. Which of these is the proximate cause of
    neuronal death is not settled; tRNA modification is the best-characterized
    activity and is tagged here as the representative process, but the
    cytoskeletal and trafficking roles are equally implicated and the field has
    not resolved whether Elongator has genuinely distinct functions or whether
    one primary defect produces the rest.
  genes:
  - preferred_term: ELP1 (formerly IKBKAP)
    term:
      id: hgnc:5959
      label: ELP1
  biological_processes:
  - preferred_term: tRNA wobble uridine modification
    term:
      id: GO:0002098
      label: tRNA wobble uridine modification
    modifier: DECREASED
  molecular_functions:
  - preferred_term: Elongator complex tRNA-modifying activity
    description: >-
      The activity is the assembled complex's, not ELP1's own: ELP1 is the
      scaffolding subunit and carries no catalytic site, so depleting it lowers
      the amount of assembled Elongator and with it the complex's tRNA-modifying
      catalysis. GO has no molecular-function term for the wobble-uridine
      chemistry specifically — the wobble terms are all biological processes, and
      the available tRNA-modifying activities name acetyl- or methyltransferase
      chemistries Elongator does not perform — so the broader tRNA-acting
      catalytic activity is bound here and the process specificity is carried by
      the biological_processes term above.
    term:
      id: GO:0140101
      label: catalytic activity, acting on a tRNA
    modifier: DECREASED
  downstream:
  - target: Failed Development and Innervation of Sensory and Autonomic Neurons
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Elongator deficiency impairs neurogenesis, target-tissue innervation, and
      neuronal survival. The intermediate steps between the biochemical deficit
      and the cellular failure are not established, which is why this edge is
      typed as having unknown intermediates.
    evidence:
    - reference: PMID:26769677
      reference_title: "Sensory and autonomic deficits in a new humanized mouse model of familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: "Recent in vivo studies highlighted that the loss of IKAP/ELP1 leads to neuronal cell death as a consequence of failed tissue innervation rather than abnormal neuronal migration"
      explanation: Places failed target innervation, not migration failure, between ELP1 loss and neuronal death.
  evidence:
  - reference: PMID:30905397
    reference_title: "ELP1 Splicing Correction Reverses Proprioceptive Sensory Loss in Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "ELP1 is the scaffolding member of the six-subunit human Elongator complex"
    explanation: Establishes ELP1's role as the complex's scaffolding subunit, so its depletion is an Elongator deficiency.
  - reference: PMID:26769677
    reference_title: "Sensory and autonomic deficits in a new humanized mouse model of familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "The Elongator complex is an evolutionary highly conserved protein complex that participates in distinct cellular processes, including transcriptional elongation, acetylation of cytoskeletal"
    explanation: Enumerates the Elongator activities compromised by ELP1 depletion, including the tRNA modification tagged on this node.
  - reference: PMID:30905397
    reference_title: "ELP1 Splicing Correction Reverses Proprioceptive Sensory Loss in Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: BACKGROUND
    snippet: "which is a highly conserved protein complex that participates in distinct cellular processes including transcriptional elongation, acetylation of cytoskeletal α-tubulin, and tRNA modification"
    explanation: >-
      Names tRNA modification among the Elongator complex's characterized
      activities, which is the catalytic-activity-on-a-tRNA molecular function
      bound on this node. Graded IN_VITRO because the quoted sentence reports the
      biochemical characterization of the complex rather than a clinical or
      whole-animal observation, and BACKGROUND because it sits in this mouse
      study's introduction restating established work.
- name: Failed Development and Innervation of Sensory and Autonomic Neurons
  biological_scale: CELLULAR
  description: >-
    Sensory, sympathetic, and parasympathetic neurons are generated in
    insufficient numbers and fail to innervate their targets. This is a
    developmental lesion present at birth, which is what distinguishes familial
    dysautonomia from the adult-onset, length-dependent dying-back
    neuropathies: the deficit in nociceptive and autonomic neurons predates
    symptoms rather than accumulating from them. Proprioceptors are the
    exception and arise normally.
  cell_types:
  - preferred_term: Sensory neuron
    term:
      id: CL:0000101
      label: sensory neuron
  - preferred_term: Autonomic neuron
    term:
      id: CL:0000107
      label: autonomic neuron
  biological_processes:
  - preferred_term: peripheral nervous system neuron development
    term:
      id: GO:0048935
      label: peripheral nervous system neuron development
    modifier: DECREASED
  downstream:
  - target: Absence of Fungiform Papillae
    causal_link_type: DIRECT
    description: >-
      Fungiform papillae carry gustatory and somatosensory receptors whose
      innervation never forms, so the papillae themselves do not develop. This
      edge is why the sign is present from infancy and is diagnostically useful
      in a newborn.
  - target: Alacrima
    causal_link_type: DIRECT
    description: >-
      Parasympathetic secretomotor innervation of the lacrimal gland fails to
      develop, so overflow tearing is absent from birth.
  - target: Progressive Sensory and Autonomic Neuron Depletion
    causal_link_type: DIRECT
    description: >-
      A population that starts numerically deficient and then degenerates
      throughout life arrives at severe depletion; the developmental failure
      sets the starting point for the lifelong attrition.
    evidence:
    - reference: PMID:20301359
      reference_title: "Familial Dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Familial dysautonomia, which affects the development and survival of sensory, sympathetic, and parasympathetic neurons, is a debilitating disorder present from birth. Neuronal degeneration progresses throughout life."
      explanation: States both halves of this edge — a developmental deficit present at birth, followed by lifelong progressive degeneration.
  evidence:
  - reference: PMID:624961
    reference_title: "Quantitative studies of dorsal root ganglia and neuropathologic observations on spinal cords in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Intrauterine development and postnatal maintenance of dorsal root ganglion neurons are abnormal in familial dysautonomia"
    explanation: Autopsy neuropathology establishes that the dorsal root ganglion lesion begins in utero rather than being purely degenerative.
  - reference: PMID:30905397
    reference_title: "ELP1 Splicing Correction Reverses Proprioceptive Sensory Loss in Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "showed that although Elp1 was required for the development of the pain- and temperature-receptive neurons, proprioceptors arise and differentiate normally"
    explanation: Neural-crest conditional knockout data separate the developmental lesion (nociceptors) from the postnatal one (proprioceptors), the distinction this node records.
- name: Progressive Sensory and Autonomic Neuron Depletion
  biological_scale: TISSUE
  description: >-
    Dorsal root ganglia are markedly depleted of neurons even in the youngest
    patients and lose more with age, and the spinal afferent pathways they feed
    are correspondingly denuded. This is the single lesion from which almost
    every clinical feature of the disease follows, and the quantitative
    neuropathology is unusually stark: roughly a tenth of the expected neuron
    count in a cervical dorsal root ganglion.
  cell_types:
  - preferred_term: Dorsal root ganglion sensory neuron
    term:
      id: CL:1001451
      label: sensory neuron of dorsal root ganglion
  biological_processes:
  - preferred_term: neuron death
    term:
      id: GO:0008219
      label: cell death
    modifier: INCREASED
  downstream:
  - target: Afferent Baroreflex and Chemoreflex Failure
    causal_link_type: DIRECT
    description: >-
      Baroreceptor and chemoreceptor traffic reaches the brainstem through
      glossopharyngeal and vagal afferents; losing those afferent neurons
      removes the input side of both reflex arcs.
    evidence:
    - reference: PMID:37204536
      reference_title: "Familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Patients have excessive blood pressure variability due to the failure of the IXth and Xth cranial nerves to carry baroreceptor signals."
      explanation: Names the specific afferent nerves whose failure produces the blood-pressure phenotype.
  - target: Postnatal Proprioceptive Neuron Loss
    causal_link_type: DIRECT
    description: >-
      Proprioceptors are part of the same dorsal root ganglion population, but
      unlike nociceptors they are generated normally and are lost only after
      birth.
    evidence:
    - reference: PMID:30905397
      reference_title: "ELP1 Splicing Correction Reverses Proprioceptive Sensory Loss in Familial Dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: "Therefore, unlike nociceptors, the loss of proprioceptors in FD most likely occurs postnatally, making this subpopulation of neurons an attractive target for therapeutic intervention."
      explanation: Establishes the postnatal timing of proprioceptor loss, the claim this node makes.
  - target: Retinal Ganglion Cell Degeneration
    causal_link_type: DIRECT
    description: >-
      Retinal ganglion cells are a further ELP1-dependent projection neuron
      population that dies postnatally, thinning the retinal nerve fiber layer.
    evidence:
    - reference: PMID:34908112
      reference_title: "Selective retinal ganglion cell loss and optic neuropathy in a humanized mouse model of familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: "Individuals with FD show a significant reduction in the thickness of the retinal nerve fiber layer (RNFL) due to death of retinal ganglion cells (RGCs)"
      explanation: Attributes the retinal nerve fiber layer thinning in patients to retinal ganglion cell death.
  - target: Enteric Nervous System Dysfunction
    causal_link_type: DIRECT
    description: >-
      The enteric nervous system is another ELP1-dependent neural-crest
      derivative whose formation and maintenance fail, producing the near
      universal gastrointestinal dysfunction.
    evidence:
    - reference: PMID:39138000
      reference_title: "ELP1, the Gene Mutated in Familial Dysautonomia, Is Required for Normal Enteric Nervous System Development and Maintenance and for Gut Epithelium Homeostasis."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "We show here that not only is Elp1 required for the normal formation of the ENS, but it is also required in adulthood for the regulation of both neuronal and non-neuronal cells and for target innervation in both the mucosa and in intestinal smooth muscle."
      explanation: Establishes ELP1 as required both for enteric nervous system formation and for its adult maintenance.
  - target: Impaired Pain and Temperature Sensation
    causal_link_type: DIRECT
    description: >-
      Nociceptive and thermoreceptive dorsal root ganglion neurons are the
      population most deficient from birth, so the corresponding sensory
      modalities are blunted from infancy.
  - target: Neurogenic Dysphagia and Recurrent Aspiration
    causal_link_type: DIRECT
    description: >-
      Loss of oropharyngeal sensory afferents and of the autonomic control of
      swallowing produces an incoordinate, unprotected swallow.
  evidence:
  - reference: PMID:624961
    reference_title: "Quantitative studies of dorsal root ganglia and neuropathologic observations on spinal cords in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neurons in dorsal root ganglia are found to be markedly diminished in the youngest patients and slow degeneration causes further depletion with age."
    explanation: Direct human neuropathological evidence for both the early deficit and the lifelong progression.
  - reference: PMID:624961
    reference_title: "Quantitative studies of dorsal root ganglia and neuropathologic observations on spinal cords in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Quantitative studies on C8 dorsal root ganglia show the normal neuron content to be between 42,500 and 53,600. In 3 patients with familial dysautonomia the range was 4,090-8,590 with the smallest number being in the oldest patient."
    explanation: Quantifies the depletion and shows the smallest count in the oldest patient, the progression this node asserts.
  - reference: PMID:624961
    reference_title: "Quantitative studies of dorsal root ganglia and neuropathologic observations on spinal cords in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Lateral root entry zones and Lissauer's tracts are severely depleted of axons."
    explanation: Shows the central projections of the depleted dorsal root ganglion neurons are correspondingly lost.
- name: Afferent Baroreflex and Chemoreflex Failure
  biological_scale: ORGANISM
  description: >-
    Loss of the afferent limb of the baroreflex leaves blood pressure without
    feedback control, producing both orthostatic hypotension and unopposed
    sympathetic surges. The parallel loss of chemoreceptor afferents abolishes
    the ventilatory response to hypoxia and blunts it to hypercapnia, so
    hypoxia produces paradoxical hypoventilation with hypotension and
    bradycardia instead of the normal defensive response. The efferent
    sympathetic apparatus is comparatively intact, which is why the failure
    manifests as uncontrolled output rather than as absent output.
  downstream:
  - target: Dysautonomic Crises
    causal_link_type: DIRECT
    description: >-
      Without baroreceptor feedback, sympathetic outflow is not restrained, and
      the resulting catecholamine surge is the crisis.
    evidence:
    - reference: PMID:36381719
      reference_title: "Experience With Dexmedetomidine Use in the Treatment of Dysautonomic Crisis in Familial Dysautonomia: An Off-Label Use."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The etiology of such crises is supposed to be a consequence of the inability to control sympathetic overflow due to damage to the afferent neurons carrying baroreceptor inputs to the central nervous system."
      explanation: States the causal step from afferent baroreceptor damage to uncontrolled sympathetic overflow.
  - target: Sleep-Disordered Breathing
    causal_link_type: DIRECT
    description: >-
      Chemoreflex failure matters most during sleep, when the conscious
      override of respiratory drive is withdrawn.
    evidence:
    - reference: PMID:30890343
      reference_title: "Chemoreflex failure and sleep-disordered breathing in familial dysautonomia: Implications for sudden death during sleep."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Impaired ventilatory control due to chemoreflex failure acquires special relevance during sleep when conscious control of respiration withdraws."
      explanation: States why chemoreflex failure produces a sleep-specific respiratory phenotype.
  - target: Blood Pressure Instability
    causal_link_type: DIRECT
    description: >-
      An open-loop pressure control system swings between orthostatic
      hypotension and paroxysmal hypertension.
  evidence:
  - reference: PMID:30890343
    reference_title: "Chemoreflex failure and sleep-disordered breathing in familial dysautonomia: Implications for sudden death during sleep."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In patients with familial dysautonomia, ventilatory responses to hypercapnia are reduced, and to hypoxia are almost absent."
    explanation: Quantifies the chemoreflex lesion — hypoxic response essentially abolished, hypercapnic response reduced.
  - reference: PMID:30890343
    reference_title: "Chemoreflex failure and sleep-disordered breathing in familial dysautonomia: Implications for sudden death during sleep."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In response to hypoxia, these patients develop paradoxical hypoventilation, hypotension, bradycardia, and potentially, death."
    explanation: Documents the paradoxical, potentially fatal response to hypoxia that follows chemoreflex failure.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients have dramatic blood pressure instability due to baroreflex failure, chronic kidney disease, and impaired swallowing leading to recurrent aspiration pneumonia, which results in chronic lung disease."
    explanation: Attributes the blood-pressure instability specifically to baroreflex failure.
- name: Postnatal Proprioceptive Neuron Loss
  biological_scale: TISSUE
  description: >-
    Muscle-spindle afferents are lost after birth, removing proprioceptive
    feedback. This is the mechanistic origin of three features that look
    unrelated clinically — areflexia, gait ataxia, and kyphoscoliosis — since
    the stretch reflex arc, balance, and the postural control of the growing
    spine all depend on the same afferent signal. Because these neurons are
    present at birth and lost later, they are the population most plausibly
    rescuable by a postnatal splice-modulating drug.
  cell_types:
  - preferred_term: Proprioceptive dorsal root ganglion neuron
    term:
      id: CL:1001451
      label: sensory neuron of dorsal root ganglion
  downstream:
  - target: Gait Ataxia
    causal_link_type: DIRECT
  - target: Areflexia
    causal_link_type: DIRECT
  - target: Kyphoscoliosis
    causal_link_type: DIRECT
    description: >-
      Poor proprioceptive control of trunk posture during growth produces the
      early-onset spinal deformity.
  evidence:
  - reference: PMID:30905397
    reference_title: "ELP1 Splicing Correction Reverses Proprioceptive Sensory Loss in Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "A lack of afferent signaling from the muscle spindles accounts for the absence of deep tendon reflexes and for gait ataxia."
    explanation: Links muscle-spindle afferent loss to both areflexia and gait ataxia, two of this node's three downstream targets.
  - reference: PMID:30905397
    reference_title: "ELP1 Splicing Correction Reverses Proprioceptive Sensory Loss in Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "Clinically, many of the debilitating aspects of the disease are related to a progressive loss of proprioception; this loss leads to severe gait ataxia, spinal deformities, and respiratory insufficiency due to neuromuscular incoordination."
    explanation: Establishes proprioceptive loss as progressive and as the common origin of gait ataxia and spinal deformity.
- name: Retinal Ganglion Cell Degeneration
  biological_scale: TISSUE
  description: >-
    Retinal ganglion cells die progressively, thinning the retinal nerve fiber
    layer and the macular ganglion cell and inner plexiform layers. The
    resulting optic neuropathy is neuro-ophthalmic rather than corneal in
    origin — it occurs in patients with no corneal complications at all — which
    distinguishes it from the separate dry-eye and corneal disease that
    alacrima causes.
  cell_types:
  - preferred_term: Retinal ganglion cell
    term:
      id: CL:0000740
      label: retinal ganglion cell
  downstream:
  - target: Progressive Optic Neuropathy
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:34908112
    reference_title: "Selective retinal ganglion cell loss and optic neuropathy in a humanized mouse model of familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "recent detailed studies have shown that decreased visual acuity, loss of central vision and temporal optic nerve pallor occur in FD patients even without any corneal complications, suggesting a neuro-ophthalmic nature of the disease"
    explanation: Establishes that the visual loss is neuro-ophthalmic and not secondary to the corneal disease of alacrima.
  - reference: PMID:33180192
    reference_title: "Longitudinal changes in the macula and optic nerve in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The rate of change for average RNFL and average GCIPL thicknesses were significant before reaching a plateau at the age of 26.2 for RNFL and 24.8 for GCIPL"
    explanation: Longitudinal OCT in 91 patients quantifies the progressive retinal ganglion cell layer loss and shows it plateaus in the mid-twenties.
- name: Enteric Nervous System Dysfunction
  biological_scale: TISSUE
  description: >-
    Enteric neurons are reduced and mucosal and smooth-muscle innervation is
    abnormal, giving dysmotility and gastroesophageal reflux. A mouse in which
    Elp1 was deleted only in neurons still developed a disorganized mucus layer
    and bacterial infiltration of the mucosa, so the epithelial barrier defect
    is downstream of the neuronal lesion rather than a parallel effect of ELP1
    loss in epithelium.
  cell_types:
  - preferred_term: Autonomic (enteric) neuron
    term:
      id: CL:0000107
      label: autonomic neuron
  downstream:
  - target: Gastrointestinal Dysmotility
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:39138000
    reference_title: "ELP1, the Gene Mutated in Familial Dysautonomia, Is Required for Normal Enteric Nervous System Development and Maintenance and for Gut Epithelium Homeostasis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The fact that deletion of Elp1 exclusively in neurons is sufficient to alter the intestinal epithelium and perturb the intestinal epithelial barrier highlights a critical role for neurons in regulating GI epithelium homeostasis."
    explanation: Neuron-restricted deletion shows the epithelial barrier defect is a consequence of the enteric neuronal lesion.
  - reference: PMID:39138000
    reference_title: "ELP1, the Gene Mutated in Familial Dysautonomia, Is Required for Normal Enteric Nervous System Development and Maintenance and for Gut Epithelium Homeostasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "Virtually all patients report gastrointestinal (GI) dysfunction"
    explanation: Establishes that gastrointestinal dysfunction is essentially universal in patients.
- name: Neurogenic Dysphagia and Recurrent Aspiration
  biological_scale: ORGANISM
  description: >-
    Impaired swallowing, itself a consequence of the sensory and autonomic
    lesion in the oropharynx and of gastroesophageal reflux, leads to repeated
    aspiration. This is the pathway to chronic lung disease and one of the
    leading causes of death, and it is the node most amenable to prevention by
    feeding and airway management.
  downstream:
  - target: Recurrent Aspiration Pneumonia and Chronic Lung Disease
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:37204536
    reference_title: "Familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neurogenic dysphagia causes frequent aspiration leading to chronic pulmonary disease."
    explanation: States the chain from neurogenic dysphagia through aspiration to chronic lung disease.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Managing neurogenic dysphagia with effective protection of the airway passages and prompt treatment of aspiration pneumonias is necessary to prevent respiratory failure."
    explanation: Identifies this node as the intervention point that prevents respiratory failure.
phenotypes:
- category: Oral
  name: Absence of Fungiform Papillae
  diagnostic: true
  description: >-
    The tongue is smooth and lacks fungiform papillae. This is one of the
    historical cardinal diagnostic criteria and is present from infancy, making
    inspection of the tongue a bedside screening manoeuvre in a newborn of
    Ashkenazi Jewish ancestry. In the original series no fungiform papillae were
    found in any of 30 patients, and vallate papillae were also absent in the
    ten patients examined for them.
  phenotype_term:
    preferred_term: Absence of fungiform papillae of the tongue
    term:
      id: HP:0030809
      label: Abnormal tongue morphology
  evidence:
  - reference: PMID:14245781
    reference_title: "ABSENCE OF TASTE-BUD PAPILLAE IN FAMILIAL DYSAUTONOMIA."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "No fungiform papillae could be found on the tongues of 30 patients with familial dysautonomia. In ten of these patients a search for vallate papillae was made, but none were found."
    explanation: Direct observation establishing the absence of fungiform papillae in every patient examined.
  - reference: PMID:14245781
    reference_title: "ABSENCE OF TASTE-BUD PAPILLAE IN FAMILIAL DYSAUTONOMIA."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Inspection of the tongue may thus be useful for diagnosing this rare disease, even in infants."
    explanation: Supports the diagnostic use of the sign, including in infancy.
- category: Ophthalmologic
  name: Alacrima
  diagnostic: true
  description: >-
    Absence of overflow tears with emotional crying, present from birth and a
    cardinal diagnostic criterion. Distinct from the separate, later optic
    neuropathy, although the resulting dry eye contributes to corneal
    complications.
  phenotype_term:
    preferred_term: Alacrima
    term:
      id: HP:0000522
      label: Alacrima
  sequelae:
  - target: Corneal Opacity and Neurotrophic Keratopathy
    causal_link_type: DIRECT
    description: >-
      Without basal, reflex and emotional tear secretion the cornea loses its
      tear film, which is the deficit that ocular lubrication in this entry's
      treatments is aimed at replacing.
    evidence:
    - reference: PMID:25323828
      reference_title: "Current treatments in familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Corneal opacities, neurotrophic keratopathy (i.e., corneal damage as a result of poor tear secretion and corneal hypoesthesia)"
      explanation: Names poor tear secretion as one of the two causes of the corneal damage.
    - reference: PMID:25323828
      reference_title: "Current treatments in familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Decreased secretion of basal, reflex, and emotional tears is one of the diagnostic features of FD."
      explanation: Establishes the tear-secretion deficit that is the upstream end of this edge.
  evidence:
  - reference: PMID:21775922
    reference_title: "Kinetin improves IKBKAP mRNA splicing in patients with familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "Affected patients have characteristic alacrima, depressed tendon reflexes and decreased pain and temperature perception, as well as gastrointestinal dysmotility"
    explanation: Names alacrima as a characteristic feature alongside the other cardinal signs.
  - reference: PMID:26769677
    reference_title: "Sensory and autonomic deficits in a new humanized mouse model of familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "absence of fungiform papillae on the tongue, decreased deep-tendon reflexes, defective lacrimation and impaired pain and temperature perception"
    explanation: Lists defective lacrimation among the common clinical features of the disease.
- category: Neurologic
  name: Impaired Pain and Temperature Sensation
  diagnostic: true
  description: >-
    Pain and temperature perception are blunted from infancy, reflecting the
    congenital deficit of small-fibre nociceptive and thermoreceptive neurons.
    Temperature sensation is impaired from the outset while pain loss worsens
    with age, matching the mixed developmental-plus-degenerative character of
    the underlying lesion. The insensitivity permits unperceived thermal
    injuries and neuropathic joint damage.
  phenotype_term:
    preferred_term: Impaired pain sensation
    term:
      id: HP:0007328
      label: Impaired pain sensation
  sequelae:
  - target: Neuropathic Joints and Thermal Injuries
    causal_link_type: DIRECT
    description: >-
      Absent protective sensation allows repeated unperceived injury to joints
      and skin.
  - target: Corneal Opacity and Neurotrophic Keratopathy
    causal_link_type: DIRECT
    description: >-
      Corneal hypoesthesia is the ocular instance of the same protective-sensory
      loss: an insensate cornea does not register abrasion, so injury goes
      unreported and unprotected. This is the second of the two causes the
      source names, alongside the tear deficit from alacrima, which is why the
      corneal phenotype has two upstream edges rather than one.
    evidence:
    - reference: PMID:25323828
      reference_title: "Current treatments in familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Corneal opacities, neurotrophic keratopathy (i.e., corneal damage as a result of poor tear secretion and corneal hypoesthesia)"
      explanation: Names corneal hypoesthesia as the second cause of the corneal damage.
  evidence:
  - reference: PMID:624961
    reference_title: "Quantitative studies of dorsal root ganglia and neuropathologic observations on spinal cords in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Temperature sensation is markedly impaired from infancy in familial dysautonomia. Loss of pain sensation is prominent and worsens with age."
    explanation: Separates the congenital temperature deficit from the progressive pain loss, and correlates both with the dorsal root ganglion neuron counts in the same study.
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals have gastrointestinal dysfunction, autonomic crises (i.e., hypertensive vomiting attacks), recurrent pneumonia, altered pain sensitivity, altered temperature perception, and blood pressure instability."
    explanation: GeneReviews lists altered pain and temperature perception among the defining clinical features.
- category: Musculoskeletal
  name: Neuropathic Joints and Thermal Injuries
  description: >-
    Charcot-type neuropathic arthropathy and burns follow from the loss of
    protective pain and temperature sensation.
  phenotype_term:
    preferred_term: Neuropathic (Charcot) arthropathy
    term:
      id: HP:0002821
      label: Neuropathic arthropathy
  evidence:
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Diminished pain and temperature perception result in neuropathic joints and thermal injuries."
    explanation: States the causal step from the sensory deficit to neuropathic joints and thermal injury.
- category: Cardiovascular
  name: Dysautonomic Crises
  diagnostic: true
  description: >-
    Paroxysmal hyperadrenergic episodes of severe hypertension, tachycardia,
    skin blotching, sweating, flushing, retching and intractable vomiting, with
    associated behavioural change. They occur in all patients and are the
    disease's most characteristic acute event. They are not a stress response
    but a control failure: with no baroreceptor feedback, sympathetic outflow
    has nothing restraining it.
  phenotype_term:
    preferred_term: Episodic hypertension (dysautonomic crisis)
    term:
      id: HP:0000875
      label: Episodic hypertension
  sequelae:
  - target: Cyclic Vomiting
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:37204536
    reference_title: "Familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "consisting of brisk episodes of severe hypertension, tachycardia, skin blotching, retching, and vomiting occur in all patients"
    explanation: Describes the crisis phenotype and establishes that it occurs in every patient.
  - reference: PMID:36381719
    reference_title: "Experience With Dexmedetomidine Use in the Treatment of Dysautonomic Crisis in Familial Dysautonomia: An Off-Label Use."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The features of dysautonomic crises are hypertension, tachycardia, vomiting, sweating, flushing, and behavioral changes."
    explanation: Enumerates the crisis features, including the sweating, flushing, and behavioural change.
- category: Gastrointestinal
  name: Cyclic Vomiting
  description: >-
    Recurrent hypertensive vomiting attacks, the gastrointestinal component of
    the dysautonomic crisis and often the presentation that brings a patient to
    the emergency department.
  phenotype_term:
    preferred_term: Episodic vomiting
    term:
      id: HP:0002572
      label: Episodic vomiting
  evidence:
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "autonomic crises (i.e., hypertensive vomiting attacks)"
    explanation: GeneReviews defines the autonomic crisis in terms of its hypertensive vomiting attacks.
- category: Cardiovascular
  name: Blood Pressure Instability
  description: >-
    Blood pressure swings widely between orthostatic hypotension and paroxysmal
    hypertension because the afferent limb of the baroreflex is missing. The
    lability rather than the absolute level is the problem, and it makes
    pregnancy high risk and contributes to early target-organ damage.
  phenotype_term:
    preferred_term: Orthostatic hypotension with paroxysmal hypertension
    term:
      id: HP:0004926
      label: Orthostatic hypotension due to autonomic dysfunction
  sequelae:
  - target: Chronic Kidney Disease
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Paroxysmal hypertension is present from birth and tracks with faster loss
      of renal function, so the lability is treated as a driver of the renal
      damage rather than only a comorbid finding. The cited relationship is an
      association observed in patients, and the intervening steps between
      pressure swings and nephron loss are not established, which is why this
      edge is typed as having unknown intermediates.
    evidence:
    - reference: PMID:25323828
      reference_title: "Current treatments in familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Paroxysmal hypertension occurs from birth and is associated with a faster progression of renal damage"
      explanation: Links the paroxysmal hypertensive component of the blood-pressure phenotype to the rate of renal damage.
  evidence:
  - reference: PMID:37204536
    reference_title: "Familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients have excessive blood pressure variability due to the failure of the IXth and Xth cranial nerves to carry baroreceptor signals."
    explanation: Attributes the blood-pressure variability to failure of the baroreceptor afferents.
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Pregnancies in women with FD are considered high risk because of blood pressure lability."
    explanation: Documents blood-pressure lability and its consequence for pregnancy management.
- category: Renal
  name: Chronic Kidney Disease
  description: >-
    Progressive loss of renal function is a frequent problem and is named
    alongside baroreflex failure and dysphagia in this disease's cardinal
    clinical picture, so it is a defining organ complication rather than an
    incidental one. Two contributions are described and they are not mutually
    exclusive: the blood-pressure lability itself, since paroxysmal hypertension
    from birth tracks with faster renal damage, and a developmental component,
    since renal patterning defects are over-represented and suggest ELP1
    deficiency also affects kidney development. The relationship then runs both
    ways, because sustained supine hypertension is usual once chronic kidney
    disease is advanced. Two management consequences follow: creatinine
    understates the glomerular filtration rate because muscle mass is low, and
    high-dose fludrocortisone given for orthostatic hypotension accelerates the
    renal decline.
  phenotype_term:
    preferred_term: Chronic kidney disease
    term:
      id: HP:0012622
      label: Chronic kidney disease
    clinical_course: PROGRESSIVE
  frequency: FREQUENT
  evidence:
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients have dramatic blood pressure instability due to baroreflex failure, chronic kidney disease, and impaired swallowing leading to recurrent aspiration pneumonia, which results in chronic lung disease."
    explanation: Names chronic kidney disease among the cardinal organ complications of the disease.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Chronic renal failure is a frequent problem in patients with FD."
    explanation: >-
      Source for the frequency value. Author wording "frequent" maps to FREQUENT
      under the dismech qualitative mapping (docs/frequency-evidence-guidelines.md
      Pattern C). No percentage or cohort denominator is reported for renal
      failure in this review.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sustained supine hypertension is usually present in FD patients with advanced chronic kidney disease"
    explanation: Establishes the reverse arm of the relationship — advanced renal disease brings sustained supine hypertension, not only lability.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There is an increased incidence of renal patterning defects in FD, suggesting that IKAP (ELP-1) deficiency may also affect kidney development."
    explanation: Supports the developmental contribution recorded in this phenotype's description, which the review itself states as a suggestion rather than an established mechanism.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Creatinine may not accurately reflect glomerular filtration rate as muscle mass is often abnormally low in these patients."
    explanation: Supports the measurement caveat recorded in this phenotype's description.
- category: Respiratory
  name: Sleep-Disordered Breathing
  description: >-
    Almost every patient has some degree of sleep-disordered breathing — 85% of
    adults and 95% of children. Obstructive events predominate in adults while
    central events are more severe and frequent in children, consistent with the
    chemoreflex rather than purely anatomical origin.
  phenotype_term:
    preferred_term: Sleep apnea
    term:
      id: HP:0010535
      label: Sleep apnea
  sequelae:
  - target: Sudden Unexpected Death During Sleep
    causal_link_type: DIRECT
    description: >-
      Untreated obstructive sleep apnea is one of the strongest identified risk
      factors for sudden death during sleep in this population.
  evidence:
  - reference: PMID:30890343
    reference_title: "Chemoreflex failure and sleep-disordered breathing in familial dysautonomia: Implications for sudden death during sleep."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Overall, almost all adult (85%) and pediatric (95%) patients have some degree of sleep-disordered breathing."
    explanation: Quantifies the near-universal prevalence in both age groups.
  - reference: PMID:30890343
    reference_title: "Chemoreflex failure and sleep-disordered breathing in familial dysautonomia: Implications for sudden death during sleep."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Obstructive apnea events are more frequent in adults, whereas central apnea events are more severe and frequent in children."
    explanation: Documents the age-dependent obstructive-versus-central pattern this phenotype records.
- category: Respiratory
  name: Sudden Unexpected Death During Sleep
  description: >-
    The most common cause of death in this disease, with an annual incidence of
    3.4 per 1000 person-years — several times the rate of sudden unexpected
    death in epilepsy. A case-control study identified untreated obstructive
    sleep apnea, fludrocortisone treatment and plasma potassium below 4 mEq/L as
    associated risks, and nocturnal non-invasive ventilation as protective, so
    the risk is substantially modifiable.
  phenotype_term:
    preferred_term: Sudden unexpected death during sleep
    term:
      id: HP:0001699
      label: Sudden death
  evidence:
  - reference: PMID:28521050
    reference_title: "Sudden Unexpected Death During Sleep in Familial Dysautonomia: A Case-Control Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sudden unexpected death during sleep (SUDS) is the most common cause of death in patients with familial dysautonomia (FD)"
    explanation: Establishes sudden death during sleep as the leading cause of death.
  - reference: PMID:28521050
    reference_title: "Sudden Unexpected Death During Sleep in Familial Dysautonomia: A Case-Control Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "participants with SUDS were more likely to be receiving treatment with fludrocortisone (odds ratio [OR]; 95% confidence interval) (OR 29.7; 4.1-213.4), have untreated obstructive sleep apnea (OR 17.4; 1.5-193), and plasma potassium levels <4 mEq/L (OR 19.5; 2.36-161) but less likely to use noninvasive ventilation at night (OR 0.19; 0.06-0.61)."
    explanation: Gives the case-control risk estimates behind the modifiable-risk claim.
  - reference: PMID:30890343
    reference_title: "Chemoreflex failure and sleep-disordered breathing in familial dysautonomia: Implications for sudden death during sleep."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The annual incidence rate of sudden death during sleep in patients with familial dysautonomia is 3.4 per 1000 person-year, compared to 0.5-1 per 1000 person-year of sudden unexpected death in epilepsy."
    explanation: Quantifies the incidence and benchmarks it against sudden unexpected death in epilepsy.
- category: Neurologic
  name: Gait Ataxia
  description: >-
    A broad-based, ataxic gait that deteriorates over time, ending in loss of
    independent ambulation. It is sensory (proprioceptive) rather than
    cerebellar in origin, and patients themselves rate it among the most
    disabling features.
  phenotype_term:
    preferred_term: Progressive proprioceptive (sensory) gait ataxia
    term:
      id: HP:0010871
      label: Sensory ataxia
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Older individuals often have a broad-based and ataxic gait that deteriorates over time."
    explanation: Documents the broad-based ataxic gait and its progression.
  - reference: PMID:37204536
    reference_title: "Familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Progressive features of the disease include retinal nerve fiber loss and blindness, and proprioceptive ataxia with severe gait impairment."
    explanation: Identifies the ataxia as proprioceptive and groups it with the other progressive features.
- category: Neurologic
  name: Areflexia
  description: >-
    Deep tendon reflexes are depressed or absent, a direct consequence of losing
    the muscle-spindle afferent limb of the stretch reflex arc rather than of
    any motor or muscle disease.
  phenotype_term:
    preferred_term: Areflexia
    term:
      id: HP:0001284
      label: Areflexia
  evidence:
  - reference: PMID:30890343
    reference_title: "Chemoreflex failure and sleep-disordered breathing in familial dysautonomia: Implications for sudden death during sleep."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Impaired development of primary sensory nerves results in reduced pain and temperature sensation, absent deep tendon reflexes and gait ataxia"
    explanation: Attributes absent deep tendon reflexes to the primary sensory nerve lesion.
- category: Skeletal
  name: Kyphoscoliosis
  description: >-
    Early-onset spinal deformity arising from poor proprioceptive control of
    trunk posture during growth. It is monitored lifelong and contributes to the
    restrictive component of the chronic lung disease.
  phenotype_term:
    preferred_term: Kyphoscoliosis
    term:
      id: HP:0002751
      label: Kyphoscoliosis
  evidence:
  - reference: PMID:30905397
    reference_title: "ELP1 Splicing Correction Reverses Proprioceptive Sensory Loss in Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "Individuals with FD have decreased sensitivity to pain and temperature sensation, visual loss, kyphoscoliosis, proprioceptive ataxia, and difficulties in regulating body temperature."
    explanation: Lists kyphoscoliosis among the clinical features alongside the proprioceptive ataxia it shares an origin with.
- category: Ophthalmologic
  name: Progressive Optic Neuropathy
  description: >-
    Progressive loss of the retinal nerve fibre layer and of central vision,
    with temporal optic nerve pallor, typically reaching legal blindness in the
    third decade. Optical coherence tomography shows measurable annual thinning
    that plateaus in the mid-twenties, which makes it one of the few objective
    progression markers available in this disease.
  phenotype_term:
    preferred_term: Optic atrophy with progressive visual loss
    term:
      id: HP:0000648
      label: Optic atrophy
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:34908112
    reference_title: "Selective retinal ganglion cell loss and optic neuropathy in a humanized mouse model of familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "In FD, visual impairment is usually early onset and often progresses to legal blindness in the third decade of life"
    explanation: Gives the onset and the usual endpoint of the visual phenotype.
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Optic neuropathy results in progressive vision loss."
    explanation: GeneReviews states the optic neuropathy and its progressive course.
  - reference: PMID:9176780
    reference_title: "Optic neuropathy in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Optic atrophy, which is indicative of a CNS disorder, is a rarely described manifestation of familial dysautonomia (Riley-Day syndrome)."
    explanation: An early report of optic atrophy in this disease, before longer survival made it a routinely recognized feature.
- category: Ophthalmologic
  name: Corneal Opacity and Neurotrophic Keratopathy
  description: >-
    Corneal damage arises from the two sensory-autonomic deficits acting on the
    same surface: alacrima leaves the cornea without its tear film, and corneal
    hypoesthesia removes the protective reflex that would register injury. The
    result is recurrent abrasion, ulceration and eventually permanent opacity,
    with severe opacities in roughly 30% of patients. This is a distinct cause
    of visual loss from the retinal ganglion cell optic neuropathy modelled
    separately in this entry, and the two coexist — which is why the optic
    neuropathy's own evidence is careful to note it occurs in patients with no
    corneal complications at all. It is the one ophthalmic lesion here that is
    largely preventable, by maintaining corneal moisture; corneal transplant is
    a poor salvage because wound healing and the epithelium are themselves
    defective.
  phenotype_term:
    preferred_term: Corneal opacity from neurotrophic keratopathy
    term:
      id: HP:0007957
      label: Corneal opacity
  frequency: FREQUENT
  evidence:
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Corneal opacities, neurotrophic keratopathy (i.e., corneal damage as a result of poor tear secretion and corneal hypoesthesia)"
    explanation: Establishes both the phenotype and its dual mechanism — deficient tear secretion together with corneal hypoesthesia.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Severe corneal opacities occur in around 30% of FD patients."
    explanation: >-
      Source for the frequency value. 30% falls in the FREQUENT band (30-79%).
      Note the reported figure is for *severe* opacities, so FREQUENT is a floor
      for corneal opacity of any grade rather than an estimate of it.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Some cases may require corneal transplant, but success rates are low due to poor wound healing and epithelial defects."
    explanation: Supports the claim that transplant is a poor salvage in this disease specifically, because healing and epithelium are themselves affected.
- category: Gastrointestinal
  name: Gastrointestinal Dysmotility
  description: >-
    Dysmotility with gastroesophageal reflux, reported by virtually every
    patient. It compounds the swallowing disorder by adding a reflux route to
    aspiration.
  phenotype_term:
    preferred_term: Gastrointestinal dysmotility
    term:
      id: HP:0002579
      label: Gastrointestinal dysmotility
  evidence:
  - reference: PMID:21775922
    reference_title: "Kinetin improves IKBKAP mRNA splicing in patients with familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "as well as gastrointestinal dysmotility"
    explanation: Names gastrointestinal dysmotility among the characteristic features.
  - reference: PMID:26769677
    reference_title: "Sensory and autonomic deficits in a new humanized mouse model of familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "Common symptoms include gastrointestinal dysfunction, gastroesophageal reflux, vomiting crises, recurrent pneumonia"
    explanation: Lists gastrointestinal dysfunction and reflux among the common symptoms.
- category: Respiratory
  name: Recurrent Aspiration Pneumonia and Chronic Lung Disease
  description: >-
    Repeated aspiration from neurogenic dysphagia and reflux produces recurrent
    pneumonia and, cumulatively, chronic lung disease. With sudden death during
    sleep, it is one of the two leading causes of mortality, and it is the one
    most reducible by feeding and airway management.
  phenotype_term:
    preferred_term: Recurrent aspiration pneumonia
    term:
      id: HP:0002100
      label: Recurrent aspiration pneumonia
  evidence:
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "impaired swallowing leading to recurrent aspiration pneumonia, which results in chronic lung disease"
    explanation: States the chain from impaired swallowing through recurrent aspiration pneumonia to chronic lung disease.
  - reference: PMID:30905397
    reference_title: "ELP1 Splicing Correction Reverses Proprioceptive Sensory Loss in Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "Unexplained sudden death, aspiration pneumonias, and respiratory insufficiency remain the leading causes of death."
    explanation: Establishes aspiration pneumonia among the leading causes of death.
- category: Neurologic
  name: Hypotonia with Delayed Motor Milestones
  description: >-
    Hypotonia is present early and delays the acquisition of motor milestones,
    contributing to the developmental presentation in infancy.
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  evidence:
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hypotonia contributes to delay in acquisition of motor milestones."
    explanation: GeneReviews states both the hypotonia and its developmental consequence.
- category: Neurologic
  name: Developmental Delay and Intellectual Disability
  description: >-
    Developmental delay or intellectual disability occurs in about a fifth of
    patients. It is a minority finding, so normal cognition does not argue
    against the diagnosis.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Developmental delay / intellectual disability occur in about 21% of individuals."
    explanation: Quantifies the proportion affected, supporting this as a minority rather than a defining feature.
genetic:
- name: ELP1
  gene_term:
    preferred_term: ELP1 (formerly IKBKAP)
    term:
      id: hgnc:5959
      label: ELP1
  association: Causal
  notes: >-
    ELP1 encodes the scaffolding subunit of the Elongator complex and was named
    IKBKAP (IKAP) when the disease gene was identified in 2001. Essentially the
    whole patient population carries the same founder allele, IVS20+6T>C, which
    is present on 99.5% of familial dysautonomia chromosomes and homozygous in
    99.5% of patients. The rare alternatives are missense: R696P in exon 19,
    seen only in compound heterozygotes with the major allele, and P914L in exon
    26, the first allele reported outside the Ashkenazi Jewish population and
    the finding that forced the diagnostic criteria to drop the ancestry
    requirement. Because the founder allele is so nearly universal, genotype
    does not explain the wide variation in severity, and modifier genes are the
    standing hypothesis for it.
  case_fractions:
  - population: Familial dysautonomia chromosomes
    case_fraction_percent: 99.5
    notes: Share of disease chromosomes carrying the IVS20+6T>C founder splice allele.
    evidence:
    - reference: PMID:12687659
      reference_title: "Identification of the first non-Jewish mutation in familial Dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The most common mutation, which is present on 99.5% of all FD chromosomes, is an intronic splice site mutation that results in tissue-specific skipping of exon 20."
      explanation: Quantifies the founder allele's share of disease chromosomes.
  evidence:
  - reference: PMID:11179021
    reference_title: "Familial dysautonomia is caused by mutations of the IKAP gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These findings demonstrate that mutations in the gene encoding IKAP are responsible for FD."
    explanation: Establishes ELP1 (IKAP) as the causal gene.
  - reference: PMID:11179021
    reference_title: "Familial dysautonomia is caused by mutations of the IKAP gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In individuals bearing a minor FD haplotype, a missense mutation in exon 19 disrupts a consensus serine/threonine kinase phosphorylation site. This mutation results in defective phosphorylation of IKAP."
    explanation: Documents the minor-haplotype missense allele and its functional consequence.
  - reference: PMID:12687659
    reference_title: "Identification of the first non-Jewish mutation in familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In this report, we describe the first non-Jewish IKBKAP mutation, a proline to leucine missense mutation in exon 26, P914L."
    explanation: Reports the P914L allele found outside the Ashkenazi Jewish population.
  - reference: PMID:12687659
    reference_title: "Identification of the first non-Jewish mutation in familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This mutation is of particular significance because it was identified in a patient who lacks one of the cardinal diagnostic criteria for the disease-pure Ashkenazi Jewish ancestry. In light of this fact, the diagnostic criteria for FD must be expanded."
    explanation: Supports the claim that the ancestry requirement was removed from the diagnostic criteria.
  - reference: PMID:37204536
    reference_title: "Familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although 99.5% of patients are homozygous for the founder mutation, phenotypic severity varies, suggesting that modifier genes impact expression."
    explanation: States both the homozygosity rate and the modifier-gene hypothesis for the residual variability.
inheritance:
- name: Autosomal Recessive
  description: >-
    Familial dysautonomia is autosomal recessive. Sibs of an affected
    individual carry the usual 25% / 50% / 25% recurrence risks. Because
    essentially every patient carries the same founder allele, population-based
    carrier screening in people of Ashkenazi Jewish heritage is straightforward
    and has been widely adopted.
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Familial dysautonomia is inherited in an autosomal recessive manner."
    explanation: States the mode of inheritance.
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "each sib of an affected individual has at conception a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier"
    explanation: Gives the standard autosomal recessive recurrence risks used in counselling.
prevalence:
- population: Ashkenazi Jewish population
  measure_type: CARRIER_FREQUENCY
  prevalence_class: ABOVE_1_IN_1000
  rate_per_100000: 3125.0
  notes: >-
    Measured carrier frequency 1 in 32 among 1100 full Ashkenazi Jewish
    individuals screened in Israel (34 carriers), converted to 3125 per 100,000.
  evidence:
  - reference: PMID:12885336
    reference_title: "Screening for familial dysautonomia in Israel: evidence for higher carrier rate among Polish Ashkenazi Jews."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Among the 1100 full AJ tested, 34 were found to be FD carriers (1:32)."
    explanation: Direct measurement of the carrier frequency in the general Ashkenazi Jewish population.
- population: Ashkenazi Jews of Polish descent
  measure_type: CARRIER_FREQUENCY
  prevalence_class: ABOVE_1_IN_1000
  rate_per_100000: 5555.0
  notes: >-
    1 in 18 among Ashkenazi Jews of Polish descent versus 1 in 99 among
    non-Polish Ashkenazi Jews, converted to 5555 per 100,000. The subpopulation
    difference is consistent with the founder allele's origin in the Pale of
    Settlement.
  evidence:
  - reference: PMID:12885336
    reference_title: "Screening for familial dysautonomia in Israel: evidence for higher carrier rate among Polish Ashkenazi Jews."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The incidence of mutation carriers was significantly higher in AJ of Polish descent (1:18) compared to AJ of non-Polish descent (1:99)."
    explanation: Establishes the higher carrier rate in the Polish Ashkenazi subpopulation.
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    No more than about 700 patients have been identified worldwide. Carrier
    screening has since almost eliminated new births, so the affected population
    is not expected to grow.
  evidence:
  - reference: PMID:30890343
    reference_title: "Chemoreflex failure and sleep-disordered breathing in familial dysautonomia: Implications for sudden death during sleep."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although a rare disease with no more than 700 identified cases"
    explanation: Gives the total number of identified cases worldwide.
  - reference: PMID:29290691
    reference_title: "IKBKAP/ELP1 gene mutations: mechanisms of familial dysautonomia and gene-targeting therapies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Genetic testing programs, which were established shortly after the disease-causing mutations were identified, have almost completely eliminated the birth of children with this disorder."
    explanation: Supports the claim that carrier screening has nearly stopped new births.
progression:
- phase: Congenital
  notes: >-
    The disease is expressed at birth. Absent fungiform papillae, alacrima,
    hypotonia, blunted temperature sensation and feeding difficulty are present
    from infancy, reflecting the developmental component of the neuronal lesion.
  evidence:
  - reference: PMID:37204536
    reference_title: "Familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Familial dysautonomia (FD) is an autosomal recessive hereditary sensory and autonomic neuropathy (HSAN, type 3) expressed at birth with profound sensory loss and early death."
    explanation: States that the disease is expressed at birth with profound sensory loss.
- phase: Progressive neurodegeneration
  notes: >-
    Neuronal degeneration continues throughout life. Pain sensation worsens,
    proprioceptive ataxia deepens toward loss of independent ambulation, and
    retinal nerve fibre layer thinning progresses until it plateaus in the
    mid-twenties, by which time visual loss is often at the level of legal
    blindness.
  evidence:
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neuronal degeneration progresses throughout life."
    explanation: States the lifelong progressive course.
  - reference: PMID:37204536
    reference_title: "Familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Progressive features of the disease include retinal nerve fiber loss and blindness, and proprioceptive ataxia with severe gait impairment."
    explanation: Names the specific features that progress.
- phase: Adult survival
  notes: >-
    Survival has improved with supportive care but remains reduced: about half
    of patients reach 40 years of age. The leading causes of death are sudden
    unexpected death during sleep, aspiration pneumonia, and respiratory
    insufficiency.
  evidence:
  - reference: PMID:26769677
    reference_title: "Sensory and autonomic deficits in a new humanized mouse model of familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "Despite advances in patient care, the disorder is inevitably fatal, with only 50% of patients reaching 40 years of age"
    explanation: Quantifies survival to age 40.
  - reference: PMID:30905397
    reference_title: "ELP1 Splicing Correction Reverses Proprioceptive Sensory Loss in Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "Unexplained sudden death, aspiration pneumonias, and respiratory insufficiency remain the leading causes of death."
    explanation: Names the leading causes of death.
diagnosis:
- name: Molecular genetic testing of ELP1
  description: >-
    The diagnosis is established by finding biallelic pathogenic ELP1 variants.
    Because one founder allele accounts for essentially all cases, targeted
    testing for IVS20+6T>C is usually sufficient, but the P914L report means
    ancestry is no longer a precondition for testing.
  evidence:
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diagnosis of familial dysautonomia is established in a proband with suggestive findings and biallelic pathogenic variants in ELP1 (formerly IKBKAP) identified by molecular genetic testing."
    explanation: States the molecular diagnostic standard.
- name: Inspection of the tongue for fungiform papillae
  description: >-
    A bedside examination usable in a newborn. The papillae are absent in
    essentially every patient, so a smooth tongue in an infant with alacrima and
    feeding difficulty is a strong pointer to the diagnosis.
  evidence:
  - reference: PMID:14245781
    reference_title: "ABSENCE OF TASTE-BUD PAPILLAE IN FAMILIAL DYSAUTONOMIA."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Inspection of the tongue may thus be useful for diagnosing this rare disease, even in infants."
    explanation: Establishes tongue inspection as a diagnostic manoeuvre usable in infancy.
- name: Optical coherence tomography of the retina and optic nerve head
  description: >-
    Spectral-domain OCT measurement of retinal nerve fibre layer and macular
    ganglion cell and inner plexiform layer thickness tracks the optic
    neuropathy quantitatively. It was developed for this disease specifically
    because there was no useful biomarker for clinical monitoring.
  evidence:
  - reference: PMID:33180192
    reference_title: "Longitudinal changes in the macula and optic nerve in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Familial Dysautonomia (FD) disease, lacks a useful biomarker for clinical monitoring."
    explanation: States the monitoring gap this imaging study set out to fill.
  - reference: PMID:33180192
    reference_title: "Longitudinal changes in the macula and optic nerve in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All subjects were imaged with spectral-domain Optical Coherence Tomography (OCT). Global and sectoral measurements of mean retinal nerve fiber layer (RNFL) and macular ganglion cell and inner plexiform layer (GCIPL) thickness"
    explanation: Describes the imaging modality and the measures used.
- name: Polysomnography
  description: >-
    Sleep studies identify the obstructive and central events that drive the
    risk of sudden death during sleep, and are the basis for deciding who needs
    nocturnal non-invasive ventilation. GeneReviews places sleep-disordered
    breathing under routine lifelong surveillance.
  evidence:
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "pulmonary function, sleep-disordered breathing, frequency and severity of dysautonomic crises"
    explanation: Lists sleep-disordered breathing among the parameters under routine surveillance.
  - reference: PMID:28521050
    reference_title: "Sudden Unexpected Death During Sleep in Familial Dysautonomia: A Case-Control Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We retrospectively identified patients with FD who died suddenly and unexpectedly during sleep and had undergone polysomnography within the 18-month period before death."
    explanation: Establishes polysomnography as the study used to stratify sudden-death risk in this population.
treatments:
- name: Dysautonomic Crisis Management with Benzodiazepines and Clonidine
  description: >-
    Benzodiazepines and clonidine are the conventional first-line treatment for
    a dysautonomic crisis, aimed at damping the catecholamine surge that
    baroreflex failure permits. Sedatives must be used cautiously because of the
    risk of respiratory depression in patients who already have chemoreflex
    failure.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: diazepam
      term:
        id: CHEBI:49575
        label: diazepam
    - preferred_term: clonidine
      term:
        id: CHEBI:46631
        label: clonidine
  target_mechanisms:
  - target: Dysautonomic Crises
    treatment_effect: INHIBITS
    description: >-
      These agents act on the sympathetic surge itself, not on the missing
      afferent input, so they abort crises without altering the underlying
      baroreflex lesion.
    evidence:
    - reference: PMID:36381719
      reference_title: "Experience With Dexmedetomidine Use in the Treatment of Dysautonomic Crisis in Familial Dysautonomia: An Off-Label Use."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The mainstay of treatment for dysautonomic crises is benzodiazepines and clonidine."
      explanation: Establishes benzodiazepines and clonidine as the standard crisis treatment.
  evidence:
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Therapeutic focus on FD is centered on reducing the catecholamine surges caused by baroreflex failure."
    explanation: States the therapeutic rationale this treatment implements.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sedative medications should be used cautiously due to the risk of respiratory depression."
    explanation: Documents the respiratory-depression caution recorded in this treatment's description.
- name: Dexmedetomidine for Refractory Dysautonomic Crisis
  description: >-
    An alpha-2 agonist used off-label when a crisis does not respond to
    benzodiazepines and clonidine. The evidence is case-level: a 19-year-old
    whose crisis had failed oral and intravenous labetalol, diazepam and
    clonidine resolved within hours of intravenous dexmedetomidine. This is a
    single reported case, not a trial result.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: dexmedetomidine
      term:
        id: CHEBI:4466
        label: dexmedetomidine
  target_mechanisms:
  - target: Dysautonomic Crises
    treatment_effect: INHIBITS
    description: >-
      Central alpha-2 agonism reduces sympathetic outflow, the step that
      baroreflex failure leaves unrestrained.
    evidence:
    - reference: PMID:36381719
      reference_title: "Experience With Dexmedetomidine Use in the Treatment of Dysautonomic Crisis in Familial Dysautonomia: An Off-Label Use."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "He was then treated with intravenous dexmedetomidine, and his symptoms resolved within a few hours."
      explanation: The observed crisis resolution on which this treatment claim rests.
  evidence:
  - reference: PMID:36381719
    reference_title: "Experience With Dexmedetomidine Use in the Treatment of Dysautonomic Crisis in Familial Dysautonomia: An Off-Label Use."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we present a case of a dysautonomic crisis that was resistant to the conventional treatment, treated safely and successfully with dexmedetomidine."
    explanation: Establishes the off-label use in conventionally refractory crisis, and that the evidence is a single case.
- name: Carbidopa
  description: >-
    A peripheral DOPA-decarboxylase inhibitor, and the best-evidenced
    disease-specific pharmacotherapy in this entry. Because it does not cross
    the blood-brain barrier it blocks catecholamine synthesis only outside the
    central nervous system, which is where the unrestrained release happens, and
    two randomized placebo-controlled crossover trials have tested it on the two
    halves of that problem. The 2013 antiemetic trial reduced nausea and
    retching (Class II evidence, mean 480 mg/day); the 2020 trial met both
    co-primary endpoints for blood-pressure variability at 300 and 600 mg/day
    (class Ib evidence). Its practical significance is that, unlike the
    benzodiazepines and clonidine it supplements, it causes neither sedation nor
    respiratory depression, so it is usable as continuous prophylaxis in
    patients whose chemoreflex is already failing rather than only as rescue.
    It is symptomatic, not disease-modifying: it lowers the catecholamine output
    that baroreflex failure permits and does nothing to the afferent lesion.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: carbidopa
      term:
        id: CHEBI:3395
        label: carbidopa
  target_mechanisms:
  - target: Dysautonomic Crises
    treatment_effect: INHIBITS
    description: >-
      Blocking peripheral dopa-decarboxylase lowers dopamine formation outside
      the brain, and it is the dopamine surge that drives the retching and
      vomiting component of the crisis. The randomized crossover phase measured
      both the symptom reduction and the fall in urinary dopamine excretion, so
      the mechanism and the outcome were shown in the same trial.
    evidence:
    - reference: PMID:23553478
      reference_title: "Hyperdopaminergic crises in familial dysautonomia: a randomized trial of carbidopa."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "In the double-blind phase, patients experienced significantly less nausea and retching while on carbidopa than on placebo (p < 0.03 and p < 0.02, respectively)."
      explanation: The randomized placebo-controlled crossover result on which this treatment link rests.
    - reference: PMID:23553478
      reference_title: "Hyperdopaminergic crises in familial dysautonomia: a randomized trial of carbidopa."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Twenty-four-hour urinary dopamine excretion was significantly lower while on carbidopa (147 ± 32 µg/gCr) than while on placebo (222 ± 41µg/gCr, p < 0.05)."
      explanation: Confirms target engagement — peripheral dopamine production fell — alongside the symptom benefit, which is the mechanism this link claims.
  - target: Blood Pressure Instability
    treatment_effect: INHIBITS
    description: >-
      Suppressing peripheral catecholamine synthesis also narrows the
      blood-pressure swings, since the hypertensive peaks are driven by excess
      norepinephrine release. This is a separate trial from the antiemetic one
      and its endpoints were the variability itself, not the vomiting.
    evidence:
    - reference: PMID:32654554
      reference_title: "Carbidopa for Afferent Baroreflex Failure in Familial Dysautonomia: A Double-Blind Randomized Crossover Clinical Trial."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The SD of systolic BP variability was reduced at both carbidopa doses (low dose: 17±4; high dose: 18±5 mm Hg) compared with placebo (23±7 mm Hg; P=0.0013), and there was a significant reduction in the systolic BP peaks on active treatment (P=0.0015)."
      explanation: Both co-primary endpoints of the randomized crossover trial, measuring the effect on this node directly.
    - reference: PMID:32654554
      reference_title: "Carbidopa for Afferent Baroreflex Failure in Familial Dysautonomia: A Double-Blind Randomized Crossover Clinical Trial."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Twenty-four hour urinary norepinephrine excretion, a marker of peripheral catecholamine release, was significantly suppressed on both high dose and low dose carbidopa, compared with placebo (P=0.0075)."
      explanation: Establishes the intervening step — suppressed peripheral catecholamine release — between the drug and the pressure effect.
  evidence:
  - reference: PMID:32654554
    reference_title: "Carbidopa for Afferent Baroreflex Failure in Familial Dysautonomia: A Double-Blind Randomized Crossover Clinical Trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This study provides class Ib evidence that carbidopa can reduce blood pressure variability in patients with congenital afferent baroreflex failure."
    explanation: The trial's own grading of its evidence level for this indication.
  - reference: PMID:23553478
    reference_title: "Hyperdopaminergic crises in familial dysautonomia: a randomized trial of carbidopa."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Carbidopa is a safe and effective antiemetic in patients with FD, likely by reducing the formation of dopamine outside the brain."
    explanation: The antiemetic trial's conclusion, including its own hedge ("likely") on the mechanism.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Unlike previous treatment options, carbidopa is not associated with sedation or respiratory depression, making it suitable as a long-term pharmacotherapy to prevent"
    explanation: Supports the claim that carbidopa is usable as continuous prophylaxis where the sedating alternatives are not, which is this treatment's practical advantage in a disease with chemoreflex failure.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Carbidopa blocks dopamine synthesis and was administered at a dose of 200 mg three times daily."
    explanation: Gives the mechanism and a dosing figure for the agent.
- name: Midodrine for Orthostatic Hypotension
  description: >-
    An alpha-1 adrenergic agonist that raises vascular tone, used for the
    hypotensive half of the blood-pressure phenotype. It is the one treatment
    here whose scheduling is dictated by the mechanism rather than by
    convenience: the pressor effect lasts only about three hours and peaks
    roughly an hour after an oral dose, so it is timed to activity rather than
    given on a fixed schedule. Supine hypertension is its characteristic adverse
    effect, which matters more in this disease than in most because the same
    patients already swing into paroxysmal hypertension and already have renal
    damage that pressure accelerates.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: midodrine
      term:
        id: CHEBI:6933
        label: midodrine
  target_mechanisms:
  - target: Blood Pressure Instability
    treatment_effect: MODULATES
    description: >-
      Midodrine acts on the efferent vascular side, which the disease leaves
      comparatively intact, to substitute for the missing baroreflex correction
      of a falling pressure. It addresses only the hypotensive direction of the
      lability, and can push the other way, which is why the effect here is
      modulation rather than inhibition of the node.
    evidence:
    - reference: PMID:25323828
      reference_title: "Current treatments in familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The α-1 adrenergic agonist midodrine (5–20 mg) raises blood pressure for"
      explanation: States the agent's class and its pressor effect on this node.
    - reference: PMID:25323828
      reference_title: "Current treatments in familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Midodrine | α1-receptor agonist that increases vascular tone and, therefore, blood pressure."
      explanation: The review's own pharmacology table row, naming the mechanism by which the node is affected.
  evidence:
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Since the peak effect is around 1 hour after oral administration, midodrine should be taken ∼45 minutes before physical activity, so that the pressor effect coincides with exercise-induced hypotension."
    explanation: Supports the activity-timed rather than fixed-schedule dosing recorded in this treatment's description.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "3-4 h. | Supine hypertension, goose bumps, increased urination."
    explanation: The pharmacology table's duration and adverse-effect entries for midodrine, supporting the short duration of action and supine hypertension recorded here.
- name: Nocturnal Non-Invasive Ventilation
  description: >-
    Non-invasive ventilation during sleep manages apneas and prevents
    hypercapnia in patients whose chemoreflex cannot defend ventilation
    unconsciously. In the sudden-death case-control study it was the one
    protective factor identified, while fludrocortisone treatment was associated
    with markedly higher risk — so the recommendation pairs starting ventilation
    with stopping fludrocortisone.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: Non-Invasive Mechanical Ventilation
    term:
      id: NCIT:C171457
      label: Non-Invasive Mechanical Ventilation
  target_mechanisms:
  - target: Sleep-Disordered Breathing
    treatment_effect: INHIBITS
    description: >-
      Ventilatory support substitutes for the absent chemoreflex drive during
      sleep, the interval in which the reflex lesion is unmasked.
    evidence:
    - reference: PMID:25323828
      reference_title: "Current treatments in familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Non-invasive ventilation during sleep effectively manages apneas and prevents hypercapnia."
      explanation: States the effect of nocturnal non-invasive ventilation on the sleep-disordered breathing node.
  - target: Sudden Unexpected Death During Sleep
    treatment_effect: INHIBITS
    description: >-
      Nocturnal ventilation was protective against sudden death in the
      case-control study, and its initiation is the study's primary preventive
      recommendation.
    evidence:
    - reference: PMID:28521050
      reference_title: "Sudden Unexpected Death During Sleep in Familial Dysautonomia: A Case-Control Study."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Initiation of noninvasive ventilation when required and discontinuation of fludrocortisone treatment may reduce the high incidence rate of SUDS in patients with FD."
      explanation: The study's own recommendation that nocturnal ventilation reduces sudden death, paired with fludrocortisone withdrawal.
  evidence:
  - reference: PMID:28521050
    reference_title: "Sudden Unexpected Death During Sleep in Familial Dysautonomia: A Case-Control Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "but less likely to use noninvasive ventilation at night (OR 0.19; 0.06-0.61)"
    explanation: Quantifies the protective association between nocturnal non-invasive ventilation and survival.
- name: Feeding and Airway Management for Neurogenic Dysphagia
  description: >-
    Multidisciplinary feeding teams manage the swallowing disorder, with airway
    protection and prompt treatment of aspiration pneumonia. This is the main
    lever against the respiratory cause of death and is supportive rather than
    disease-modifying.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_mechanisms:
  - target: Neurogenic Dysphagia and Recurrent Aspiration
    treatment_effect: INHIBITS
    description: >-
      Feeding and airway management interrupt the step between the swallowing
      lesion and aspiration; they do not touch the neuronal deficit that causes
      the dysphagia.
    evidence:
    - reference: PMID:25323828
      reference_title: "Current treatments in familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Managing neurogenic dysphagia with effective protection of the airway passages and prompt treatment of aspiration pneumonias is necessary to prevent respiratory failure."
      explanation: Identifies airway protection and dysphagia management as the intervention on this node.
  evidence:
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Feeding teams manage neurogenic dysphagia; mental health professionals treat anxiety."
    explanation: Documents the multidisciplinary feeding-team model of care.
- name: Percutaneous Endoscopic Gastrostomy
  description: >-
    Gastrostomy placement is the standard answer to the feeding side of the
    swallowing lesion, used when feeding aversion and failure to thrive are not
    manageable with thickened formula and nasogastric feeding. It bypasses the
    unprotected oropharyngeal swallow rather than correcting it, which is what
    makes it a durable answer in a disease where neurogenic dysphagia persists
    for life. It also becomes the route for medication and fluids, and that
    creates a hazard specific to this disease: patients do not regulate water
    intake by thirst, so free water given through the tube can produce water
    intoxication.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Percutaneous Endoscopic Gastrostomy
    term:
      id: NCIT:C106040
      label: Percutaneous Endoscopic Gastrostomy
  target_mechanisms:
  - target: Neurogenic Dysphagia and Recurrent Aspiration
    treatment_effect: BYPASSES
    description: >-
      Enteral feeding delivers calories without passing a bolus through the
      incoordinate, unprotected swallow, so it removes the oral route by which
      aspiration occurs rather than restoring swallowing function.
    evidence:
    - reference: PMID:25323828
      reference_title: "Current treatments in familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Feeding aversion and failure to thrive are managed with percutaneous endoscopic gastrostomy (PEG) placement"
      explanation: Establishes gastrostomy placement as the management of the feeding consequences of this node.
  evidence:
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Thickened formula and nasograstric feeding may be required to manage caloric intake in infants."
    explanation: Documents the less invasive measures that precede gastrostomy in the same management sequence.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neurogenic dysphagia persists throughout life, and eating by mouth can become a challenge."
    explanation: Supports the claim that the swallowing lesion is lifelong, which is why the enteral route is durable rather than temporary.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "they should be cautioned to avoid excessive free water intake through the gastrostomy tube to avoid water intoxication."
    explanation: Documents the disease-specific hazard the gastrostomy route introduces, recorded in this treatment's description.
- name: Fundoplication
  description: >-
    An antireflux wrap, performed in 72% of patients in the US, addressing the
    gastroesophageal reflux that occurs in about three quarters of them and adds
    a second route to aspiration on top of the swallowing lesion. It is included
    here with its own evidence of limits rather than as a settled benefit: the
    review states that its effect on natural history compared with untreated
    patients is unclear, that reflux can recur, that up to 12% need a second
    operation, and that oesophageal dilatation and achalasia are increasingly
    recognized afterwards. One independent corroboration of the wrap's
    mechanical effect comes from the carbidopa antiemetic trial, where every
    enrolled patient had had a fundoplication and none could vomit — they
    retched instead, which is why that trial's endpoints were nausea and
    retching rather than vomiting.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Fundoplication
    term:
      id: NCIT:C91834
      label: Fundoplication
  target_mechanisms:
  - target: Gastrointestinal Dysmotility
    treatment_effect: INHIBITS
    description: >-
      The wrap acts on the gastroesophageal reflux component of the dysmotility
      phenotype, mechanically opposing retrograde flow. It does not touch the
      enteric neuronal lesion that produces the dysmotility, and the same
      denervated oesophagus is why dilatation and achalasia follow the procedure
      more often here than in an otherwise normal gut.
    evidence:
    - reference: PMID:25323828
      reference_title: "Current treatments in familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Gastroesophageal reflux occurs in 75% of FD patients."
      explanation: Quantifies the reflux component of this node that the procedure is aimed at.
    - reference: PMID:25323828
      reference_title: "Current treatments in familial dysautonomia."
      supports: REFUTE
      evidence_source: HUMAN_CLINICAL
      snippet: "Esophageal dilatation and achalasia (i.e., abnormal esophageal peristalsis) are increasingly recognized complications after fundoplication surgery."
      explanation: Cuts against the claim that the procedure inhibits this node overall, since two of its recognized complications are themselves oesophageal dysmotility.
  evidence:
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "fundoplication surgery has been performed in 72% of patients with FD in the US"
    explanation: Establishes how widely the procedure is used in this population.
  - reference: PMID:23553478
    reference_title: "Hyperdopaminergic crises in familial dysautonomia: a randomized trial of carbidopa."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Previous fundoplication surgery in each patient studied prevented vomiting"
    explanation: Independent observation, from a trial cohort in which every patient had had the procedure, that the wrap mechanically prevents vomiting — and the reason that trial measured retching instead.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "The impact of the fundoplication wrap on the natural history of these patients compared with that of untreated patients is still unclear."
    explanation: The review declines to credit the procedure with a change in natural history, which is evidence against treating it as an established benefit.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "GER can reoccur after the fundoplication,32 and up to 12% of patients who underwent the procedure required a second surgery."
    explanation: Quantifies the failure rate, cutting against durable benefit.
- name: Ocular Surface Lubrication
  description: >-
    Maintaining corneal moisture is the preventive treatment for the corneal
    limb of the eye disease, and it is the only ophthalmic intervention here
    that acts before damage rather than after it. The regimen is defined by
    frequency rather than by a single agent — preservative-free artificial tears
    every two to three hours, liquid gels every four to six, and a
    carboxymethylcellulose, glycerin, mineral-oil or petrolatum ointment
    overnight — because alacrima removes tear production continuously rather
    than episodically. It does nothing for the retinal ganglion cell optic
    neuropathy, which is a separate cause of visual loss in this entry.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: carboxymethylcellulose
      term:
        id: CHEBI:85146
        label: carboxymethylcellulose
  target_mechanisms:
  - target: Corneal Opacity and Neurotrophic Keratopathy
    treatment_effect: INHIBITS
    description: >-
      Topical lubrication substitutes for the missing tear film, which is one of
      the two upstream causes of the corneal damage. It does not restore corneal
      sensation, so the hypoesthesia arm of the lesion is untouched — which is
      why the treatment is preventive of surface breakdown rather than curative.
    evidence:
    - reference: PMID:25323828
      reference_title: "Current treatments in familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Therapeutic approaches focus on maintaining corneal moisture to avoid dry eye complications, including recurrent corneal abrasions, ulcers, and permanent opacities."
      explanation: States the therapeutic aim and names the corneal outcomes it is intended to prevent, which are this node's content.
  evidence:
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Treatments include preservative-free artificial tears (every 2-3 hours), liquid gels (every 4-6 hours), and ointments (e.g., carboxymethyl cellulose, glycerin, mineral oil, or white petrolatum at bedtime or every 8-12 hours)."
    explanation: Enumerates the preparations and dosing frequencies recorded in this treatment's description, including the carboxymethylcellulose bound as the therapeutic agent.
- name: Splice-Modulating Therapy (Kinetin and Derivatives)
  description: >-
    Investigational, and the only approach that targets the molecular defect.
    Kinetin shifts ELP1 splicing toward the full-length transcript. In an open
    28-day study of eight homozygous patients it raised wild-type ELP1 message
    in leukocytes with no dose escalation, establishing target engagement in
    humans but not clinical benefit. Benefit has been shown only in the
    humanized mouse. No splice-modulating agent is approved for this disease.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: kinetin
      term:
        id: CHEBI:27407
        label: kinetin
  target_mechanisms:
  - target: Tissue-Specific Skipping of ELP1 Exon 20
    treatment_effect: INHIBITS
    description: >-
      Kinetin acts on the splicing step itself, increasing the fraction of
      transcripts that retain exon 20 — the only node in this entry's chain
      upstream of the neuronal loss that a drug can currently reach.
    evidence:
    - reference: PMID:21775922
      reference_title: "Kinetin improves IKBKAP mRNA splicing in patients with familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "An increase in WT IKBKAP mRNA expression in leukocytes was noted after 8 d in six of eight individuals; after 28 d, the mean increase compared with baseline was significant (p = 0.002)."
      explanation: Demonstrates that kinetin shifts ELP1 splicing in patients, the mechanism this link claims.
  evidence:
  - reference: PMID:21775922
    reference_title: "Kinetin improves IKBKAP mRNA splicing in patients with familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This is the first report of a drug that produces in vivo mRNA splicing changes in individuals with FD and supports future long-term trials to determine whether kinetin will prove therapeutic in FD patients."
    explanation: Establishes target engagement in humans while stating explicitly that therapeutic benefit remains to be determined.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical trials of compounds that increase levels of IKAP (ELP-1) are underway and will determine whether they can reverse or slow disease progression."
    explanation: Confirms that disease-modifying efficacy was still an open question at the time of this review.
- name: Phosphatidylserine
  description: >-
    Investigational, and worth modelling separately from kinetin because its
    mechanism is different rather than merely its chemistry: kinetin shifts the
    exon 20 inclusion-to-skipping ratio, whereas phosphatidylserine raises ELP1
    transcription without altering that ratio. Both therefore converge on the
    same target — more ELP1 protein in neurons — by non-overlapping routes,
    which is the stated reason the two might be combined. Human evidence is
    early: a small number of patients showed an ELP1 rise with acceptable
    tolerability, and whether that translates into rescue or delay of optic
    atrophy and gait ataxia was still the object of ongoing long-term trials at
    the time of this review. Nothing here is a clinical outcome.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: phosphatidylserine
      term:
        id: CHEBI:18303
        label: phosphatidyl-L-serine
  target_mechanisms:
  - target: Neuronal Elongator Complex Deficiency
    treatment_effect: RESTORES
    description: >-
      Because it raises ELP1 transcription rather than correcting the splice
      ratio, phosphatidylserine acts on the protein-level deficit itself, one
      node downstream of where kinetin acts. This is the reason it is linked here
      and not to the exon 20 skipping node: the mis-splicing is unchanged.
    evidence:
    - reference: PMID:25323828
      reference_title: "Current treatments in familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "While kinetin increases the levels of correctly spliced IKAP transcripts, thus altering the ratio between exon 20 inclusion and skipping, phosphatidylserine appears to increase levels of transcription without altering the ratio."
      explanation: States the mechanistic distinction that places this treatment on the Elongator-deficiency node rather than on the splicing node.
    - reference: PMID:25323828
      reference_title: "Current treatments in familial dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Initial studies of phosphatidylserine in a small number of FD patients have demonstrated an increase in IKAP (ELP-1) levels and have shown that it is safe and well tolerated."
      explanation: The human target-engagement result — an ELP1 rise in patients — on which this link rests, with the review's own note that the sample was small.
  evidence:
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Phosphatidylserine, a phospholipidic component of cell membranes, has been shown to raise IKAP (ELP-1) levels in cell lines and animal models of FD."
    explanation: The preclinical basis for the agent. Graded IN_VITRO for the cell-line result the sentence reports; the same sentence also cites animal models, which is why the human evidence above is quoted separately rather than folded into this item.
  - reference: PMID:25323828
    reference_title: "Current treatments in familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Long-term trials are underway to determine whether raising IKAP (ELP-1) levels can rescue or delay the progressive worsening of neurological features like optic atrophy and gait ataxia."
    explanation: Establishes that clinical benefit was unresolved and under test, which is why this treatment is recorded as investigational.
- name: Genetic Counseling and Carrier Screening
  description: >-
    Counselling for autosomal recessive inheritance, with population-based
    carrier screening offered to people of Ashkenazi Jewish heritage. Screening
    has had an unusually large effect for a genetic service: it has almost
    eliminated new births with the disorder.
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Carrier screening is available on a population basis for individuals of Ashkenazi Jewish heritage."
    explanation: Documents population-based carrier screening in the at-risk population.
  - reference: PMID:29290691
    reference_title: "IKBKAP/ELP1 gene mutations: mechanisms of familial dysautonomia and gene-targeting therapies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Genetic testing programs, which were established shortly after the disease-causing mutations were identified, have almost completely eliminated the birth of children with this disorder."
    explanation: Quantifies the effect of the screening programs on disease incidence.
environmental:
- name: Hot or humid weather
  description: >-
    GeneReviews lists hot or humid weather among the circumstances to avoid
    because it exacerbates symptoms. The mechanism is not stated there, but it
    coheres with the rest of this entry: autonomic thermoregulation is defective
    — difficulty regulating body temperature is among the disease's listed
    features — so an ambient heat load is one the patient cannot compensate for,
    and the compensatory demand falls on the same sympathetic outflow that has
    no baroreflex restraining it. Recorded here as an exacerbating exposure
    rather than a trigger of the disease.
  effect: Exacerbates symptoms, including dysautonomic crises.
  exposure_term:
    preferred_term: exposure to hot or humid weather
    term:
      id: ECTO:1000007
      label: exposure to high temperature environment
  notes: >-
    Bound to the heat half only. ECTO has no humidity-exposure class: searched
    the pinned local build with `runoak -i sqlite:obo:ecto info` for `l~humid`
    (returns ENVO:01000828 humid air, ENVO:09200015 humidity of soil,
    PATO:0015009 humidity, PATO:0015010 increased humidity — all qualities or
    material entities, none an exposure event and none in the ExposureTerm
    enum), `l~humidity` (no ECTO terms), `l~moist` (no ECTO terms), and
    `l~weather` (only ECTO:1000020 exposure to weather, which is broader than
    the heat term and loses the temperature claim). XCO has only XCO:0000993
    controlled humidity, a laboratory-controlled condition rather than ambient
    humid weather. ECTO:1000007 was preferred over ECTO:1000018 exposure to
    extreme high temperature environment because the source says "hot", not
    extreme, and over ECTO:4000001 exposure to increased temperature because the
    claim is about the ambient environment rather than a temperature increase in
    an unspecified medium. The humidity sense is carried by preferred_term.
  influences_mechanisms:
  - target: Dysautonomic Crises
    environmental_effect: EXACERBATES
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Heat exposure worsens symptoms in a patient who cannot thermoregulate
      autonomically. The steps between the ambient load and a hyperadrenergic
      crisis are not established in the cited source, which states the
      exacerbation without a mechanism, so the edge is typed as having unknown
      intermediates.
    evidence:
    - reference: PMID:20301359
      reference_title: "Familial Dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The following can exacerbate symptoms: hot or humid weather; full bladder."
      explanation: GeneReviews names hot or humid weather as a symptom-exacerbating circumstance to avoid.
  evidence:
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The following can exacerbate symptoms: hot or humid weather; full bladder."
    explanation: The GeneReviews avoid-list entry establishing this exposure as symptom-exacerbating.
  - reference: PMID:30905397
    reference_title: "ELP1 Splicing Correction Reverses Proprioceptive Sensory Loss in Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "Individuals with FD have decreased sensitivity to pain and temperature sensation, visual loss, kyphoscoliosis, proprioceptive ataxia, and difficulties in regulating body temperature."
    explanation: Supports the thermoregulatory-failure rationale in this entry's description by establishing that patients have difficulty regulating body temperature. It does not itself state that heat exacerbates symptoms.
- name: Full bladder
  description: >-
    GeneReviews lists a full bladder among the circumstances to avoid because it
    exacerbates symptoms. It belongs to the same class of visceral-afferent
    stimulus that provokes hyperadrenergic episodes in other afferent-lesioned
    autonomic disorders, and it is a modifiable one — which is why it appears on
    an avoid list rather than only in a mechanism discussion. The cited source
    states the exacerbation without a mechanism and this entry does not supply
    one.
  effect: Exacerbates symptoms, including dysautonomic crises.
  exposure_term:
    preferred_term: bladder distension from urinary retention
  notes: >-
    Left unbound: neither ECTO nor XCO has a bladder-distension or
    visceral-stimulus exposure class. Searched the pinned local builds with
    `runoak -i sqlite:obo:ecto info` for `l~bladder`, `l~distension`,
    `l~distention`, `l~visceral`, `l~stretch` and `l~retention` (no ECTO terms
    for any of the six) and `l~urine` (returns only ECTO:9000202 exposure to
    purines and an unrelated enzyme-inhibitor term). `runoak -i sqlite:obo:xco
    info` for `l~distension`, `l~distention`, `l~full ` and `l~visceral` returns
    no XCO terms; `l~bladder` returns only XCO:0001279 partial bladder outlet
    obstruction, which is an outflow obstruction rather than a distended
    bladder, and `l~urin` returns XCO:0001101 urinary catheterization, which is
    the intervention that relieves this exposure rather than the exposure. No
    term beats a wrong one, so the concept is carried in preferred_term alone.
  influences_mechanisms:
  - target: Dysautonomic Crises
    environmental_effect: EXACERBATES
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      A distended bladder is an avoidable precipitant of symptom exacerbation.
      The cited source lists it without a mechanism, so no intermediate steps are
      asserted here.
    evidence:
    - reference: PMID:20301359
      reference_title: "Familial Dysautonomia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The following can exacerbate symptoms: hot or humid weather; full bladder."
      explanation: GeneReviews names a full bladder as a symptom-exacerbating circumstance to avoid.
  evidence:
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The following can exacerbate symptoms: hot or humid weather; full bladder."
    explanation: The GeneReviews avoid-list entry establishing this exposure as symptom-exacerbating.
animal_models:
- name: TgFD9;Elp1 humanized familial dysautonomia mouse
  species: Mouse
  genotype: TgFD9 human ELP1 transgene carrying IVS20+6T>C, on an Elp1 delta20/flox background
  publication: PMID:26769677
  description: >-
    The complete human ELP1 (IKBKAP) gene carrying the founder splice mutation
    was introduced as a transgene into a mouse expressing very little endogenous
    Elp1. Unlike earlier knockout attempts, this reproduces the human molecular
    defect itself — tissue-specific mis-splicing of a human transgene — rather
    than simply lowering Elp1, which is what makes it usable for testing
    splice-modulating drugs.
  modeled_mechanisms:
  - target: Tissue-Specific Skipping of ELP1 Exon 20
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: MOLECULAR
    description: >-
      The transgene reproduces the same tissue-specific exon 20 mis-splicing
      seen in patients, which is the property the model was built for.
    evidence:
    - reference: PMID:26769677
      reference_title: "Sensory and autonomic deficits in a new humanized mouse model of familial dysautonomia."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "recreates the same tissue-specific mis-splicing defect seen in FD patients"
      explanation: States that the model reproduces the human mis-splicing defect.
  - target: Failed Development and Innervation of Sensory and Autonomic Neurons
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: >-
      The mouse shows sensory and sympathetic impairment and a reduced number of
      fungiform papillae, the developmental readouts of this node.
    limitations: >-
      Mouse Ikap is only about 80% identical to human IKAP, and the phenotype is
      produced by a human transgene on a hypomorphic mouse background rather
      than by the endogenous locus, so absolute expression levels are not those
      of a patient.
    evidence:
    - reference: PMID:26769677
      reference_title: "Sensory and autonomic deficits in a new humanized mouse model of familial dysautonomia."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "recapitulates many phenotypic features of the human disease, including reduced growth rate, reduced number of fungiform papillae, spinal abnormalities, and sensory and sympathetic impairments"
      explanation: Establishes the model as informative for the sensory and autonomic developmental phenotype.
  - target: Postnatal Proprioceptive Neuron Loss
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: TISSUE
    description: >-
      The model reproduces the proprioceptive impairment seen in patients, and
      postnatal kinetin prevents the proprioceptive neuron loss and the spinal
      abnormalities that follow it — a rescue experiment that is also the
      strongest available evidence for the causal direction of this node.
    readouts:
    - name: Onset of spinal abnormalities under postnatal kinetin
      target: Postnatal Proprioceptive Neuron Loss
      direction: RESTORED
      interpretation: >-
        Preventing proprioceptive neuron loss prevents the spinal deformity,
        supporting the proprioception-to-kyphoscoliosis edge in this entry.
      evidence:
      - reference: PMID:30905397
        reference_title: "ELP1 Splicing Correction Reverses Proprioceptive Sensory Loss in Familial Dysautonomia."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Daily administration of kinetin starting at birth improves sensory-motor coordination and prevents the onset of spinal abnormalities by stopping the loss of proprioceptive neurons."
        explanation: Reports the measured rescue of proprioceptive neuron loss and of the spinal phenotype.
    evidence:
    - reference: PMID:30905397
      reference_title: "ELP1 Splicing Correction Reverses Proprioceptive Sensory Loss in Familial Dysautonomia."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "We demonstrate herein that the FD mouse TgFD9;IkbkapΔ20/flox recapitulates the proprioceptive impairment observed in individuals with FD"
      explanation: Establishes the model as informative for the proprioceptive node.
  - target: Retinal Ganglion Cell Degeneration
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: TISSUE
    description: >-
      The same mouse develops a progressive retinal phenotype, which was
      characterized specifically to support development of therapies for the
      optic neuropathy.
    limitations: >-
      The murine retina lacks a macula, so the model cannot reproduce the
      macular ganglion cell and inner plexiform layer thinning that is the main
      quantitative measure of progression in patients.
    evidence:
    - reference: PMID:34908112
      reference_title: "Selective retinal ganglion cell loss and optic neuropathy in a humanized mouse model of familial dysautonomia."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "we comprehensively characterized the progression of the retinal phenotype in this mouse, and we demonstrated that it is possible to correct ELP1 splicing defect in the retina using the splicing modulator compound (SMC) BPN-15477."
      explanation: Establishes the retinal phenotype in this model and its correctability by a splicing modulator.
  evidence:
  - reference: PMID:26769677
    reference_title: "Sensory and autonomic deficits in a new humanized mouse model of familial dysautonomia."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "This new mouse model, TgFD9; Ikbkap(Δ20/flox) was created by introducing the complete human IKBKAP transgene with the major FD splice mutation (TgFD9) into a mouse that expresses extremely low levels of endogenous Ikbkap"
    explanation: Describes the construction of the model, establishing that it carries the human founder allele.
  - reference: PMID:36809767
    reference_title: "Development of an oral treatment that rescues gait ataxia and retinal degeneration in a phenotypic mouse model of familial dysautonomia."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Remarkably, PTC258 treatment improves survival, gait ataxia, and retinal degeneration in the phenotypic FD mice."
    explanation: Shows the model responds to a brain-penetrant splicing modulator across survival, gait and retinal endpoints.
clinical_trials:
- name: NCT06148311
  phase: PHASE_II
  status: ENROLLING_BY_INVITATION
  description: >-
    Placebo-controlled study of a sublingual dexmedetomidine film for aborting
    hyperadrenergic autonomic crisis outside hospital. It matters for this entry
    because the existing dexmedetomidine evidence is a single intravenous case,
    which confines the drug to inpatient use; a sublingual film would move an
    alpha-2 agonist into the ambulatory setting where crises actually start. The
    registered aims are feasibility plus whether heart rate, blood pressure and
    oxygen saturation can predict crisis onset, so a positive result would also
    give this disease a prodromal signal it currently lacks.
  target_phenotypes:
  - preferred_term: Episodic hypertension (dysautonomic crisis)
    term:
      id: HP:0000875
      label: Episodic hypertension
  notes: >-
    Phase and recruitment status were read from the ClinicalTrials.gov v2 API
    (`designModule.phases` = PHASE2, `statusModule.overallStatus` =
    ENROLLING_BY_INVITATION); the cached record holds only the brief summary and
    does not carry either field.
  evidence:
  - reference: clinicaltrials:NCT06148311
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The purpose of this placebo controlled interventional study is to collect preliminary data on administering dexmedetomidine in patients with Familial Dysautonomia (FD) during a rapid cessation of autonomic crisis."
    explanation: The registry's own statement of the trial's design and indication, establishing that it tests dexmedetomidine against dysautonomic crisis in this disease.
  - reference: clinicaltrials:NCT06148311
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The primary aims are to assess the feasibility and evaluate if measurements of heart rate, blood pressure and oxygen saturation can predict the start of an autonomic crisis."
    explanation: Establishes the primary aims recorded in this trial's description, including the crisis-prediction objective.
differential_diagnoses:
- name: Other hereditary sensory and autonomic neuropathies
  description: >-
    Familial dysautonomia is type III of the numbered HSAN series, whose members
    share impaired pain and temperature sensation but differ in gene,
    inheritance, and the balance of sensory against autonomic involvement. HSAN
    IV (NTRK1, congenital insensitivity to pain with anhidrosis) is the closest
    clinical mimic in an infant, since it also presents with insensitivity to
    pain and autonomic signs. The distinguishing features here are the absent
    fungiform papillae, alacrima, and afferent baroreflex failure, and the
    diagnosis is settled molecularly.
  evidence:
  - reference: PMID:37204536
    reference_title: "Familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Familial dysautonomia (FD) is an autosomal recessive hereditary sensory and autonomic neuropathy (HSAN, type 3)"
    explanation: Places this disease as one type within the HSAN series from which it must be distinguished.
  - reference: PMID:20301359
    reference_title: "Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diagnosis of familial dysautonomia is established in a proband with suggestive findings and biallelic pathogenic variants in ELP1 (formerly IKBKAP) identified by molecular genetic testing."
    explanation: Supports the claim that the differential within the HSAN series is settled by molecular testing.
discussions:
- discussion_id: fd_which_elongator_activity
  prompt: >-
    Which Elongator activity — tRNA wobble-uridine modification, alpha-tubulin
    acetylation, or transcriptional elongation — is the proximate cause of
    neuronal death in familial dysautonomia, and does Elongator have genuinely
    distinct functions or one primary defect with downstream consequences?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Neuronal Elongator Complex Deficiency
  - pathophysiology#Failed Development and Innervation of Sensory and Autonomic Neurons
  rationale: >-
    The entry binds tRNA wobble-uridine modification to the Elongator deficiency
    node because it is the best-characterized activity, but that choice is a
    representative tag rather than a mechanistic verdict. ELP1 has also been
    implicated in exocytosis, cytoskeletal organization, axonal transport,
    adhesion, and migration, and the literature explicitly records that it
    remains unclear whether Elongator has distinct functions or whether its role
    in tRNA modification drives everything else. Treating the tRNA binding as
    the established cause of neuronal death would overstate what is known, which
    matters because the choice determines what a mechanism-directed therapy
    would target.
  evidence:
  - reference: PMID:26769677
    reference_title: "Sensory and autonomic deficits in a new humanized mouse model of familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "Currently, it is still not clear whether Elongator has distinct functions or whether its primary role in tRNA modification leads to multiple downstream events"
    explanation: States the open question directly — the field has not resolved whether tRNA modification is the primary defect.
  - reference: PMID:30905397
    reference_title: "ELP1 Splicing Correction Reverses Proprioceptive Sensory Loss in Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "ELP1 function has been widely investigated and has been implicated in exocytosis, cytoskeletal organization, and axonal transport, as well as cellular adhesion and migration."
    explanation: Enumerates the competing candidate functions, none of which has been shown to be the proximate cause of neuronal death.
- discussion_id: fd_phenotypic_variability_one_allele
  prompt: >-
    If 99.5% of patients are homozygous for the same founder allele, what
    accounts for the wide variation in severity between them?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - genetic#ELP1
  - pathophysiology#Tissue-Specific Skipping of ELP1 Exon 20
  rationale: >-
    This disease is close to a natural experiment in which genotype is held
    constant, so the observed severity range has to come from somewhere else.
    Modifier genes are the standing hypothesis, but the identity of any modifier
    is unknown. A second, non-exclusive candidate follows from the mechanism
    this entry models: because the allele is leaky and the skipping fraction
    varies by tissue, an individual's severity may be set by how much correctly
    spliced ELP1 their nervous system happens to make. Distinguishing the two
    matters for trial design, since ELP1 level is being used as a surrogate
    endpoint for target engagement.
  evidence:
  - reference: PMID:37204536
    reference_title: "Familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although 99.5% of patients are homozygous for the founder mutation, phenotypic severity varies, suggesting that modifier genes impact expression."
    explanation: States both halves of the gap — near-uniform genotype, variable phenotype — and names the modifier-gene hypothesis.
  - reference: PMID:37204536
    reference_title: "Familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients with FD produce variable amounts of ELP1 in different tissues, with the brain producing mostly mutant transcripts."
    explanation: Supports the alternative candidate — inter-individual variation in residual ELP1 production.
- discussion_id: fd_kinetin_mouse_to_human_gap
  prompt: >-
    Splice-modulating compounds rescue proprioceptive loss, gait ataxia and
    retinal degeneration in the humanized TgFD9 mouse, but the only human result
    is a change in leukocyte ELP1 splicing. Does correcting splicing after birth
    in humans rescue neurological phenotypes, as it does in the mouse?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - animal_models#Mouse
  - treatments#Splice-Modulating Therapy (Kinetin and Derivatives)
  - pathophysiology#Postnatal Proprioceptive Neuron Loss
  rationale: >-
    The efficacy evidence and the human evidence measure different things. In
    the mouse, kinetin given from birth prevents proprioceptive neuron loss and
    spinal abnormality, and a brain-penetrant derivative improves survival, gait
    ataxia, and retinal degeneration — phenotypic endpoints. In patients, the
    only demonstrated effect is a significant rise in wild-type ELP1 message in
    leukocytes over 28 days, which is target engagement in an accessible tissue,
    not benefit in the nervous system and not a clinical outcome. Two specific
    things do not transfer: leukocytes are among the tissues that mis-splice
    least, so a leukocyte readout is a weak proxy for the neuronal compartment
    that matters; and the mouse rescues begin at birth, whereas patients are
    typically treated later, after some of the loss has already happened. The
    mechanism gives a reason to expect timing to be decisive, since
    proprioceptors and retinal ganglion cells are the populations lost
    postnatally and therefore the ones still present to save.
  evidence:
  - reference: PMID:30905397
    reference_title: "ELP1 Splicing Correction Reverses Proprioceptive Sensory Loss in Familial Dysautonomia."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Daily administration of kinetin starting at birth improves sensory-motor coordination and prevents the onset of spinal abnormalities by stopping the loss of proprioceptive neurons."
    explanation: The mouse phenotypic rescue, obtained with treatment from birth, that the human data do not yet match.
  - reference: PMID:21775922
    reference_title: "Kinetin improves IKBKAP mRNA splicing in patients with familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This is the first report of a drug that produces in vivo mRNA splicing changes in individuals with FD and supports future long-term trials to determine whether kinetin will prove therapeutic in FD patients."
    explanation: The human result is a splicing change with therapeutic benefit explicitly still to be determined, which is the mismatch.
  - reference: PMID:37204536
    reference_title: "Familial dysautonomia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Early intervention may be critical for treatment to be successful."
    explanation: Supports the timing component of the gap — that when treatment starts may determine whether the mouse result transfers.
external_assertions:
- name: OMIM familial dysautonomia phenotype record
  source: OMIM
  assertion_type: disease_record
  external_id: OMIM:223900
  url: https://omim.org/entry/223900
  description: OMIM phenotype record for familial dysautonomia (Riley-Day syndrome, HSAN III).
- name: OMIM ELP1 gene record
  source: OMIM
  assertion_type: gene_record
  external_id: OMIM:603722
  url: https://omim.org/entry/603722
  description: OMIM gene record for ELP1 (elongator acetyltransferase complex subunit 1, formerly IKBKAP).
datasets: []

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References & Deep Research

References

3

PMID:20301359

Familial Dysautonomia.

No top-level findings curated for this source.

PMID:11179021

Familial dysautonomia is caused by mutations of the IKAP gene.

No top-level findings curated for this source.

PMID:37204536

Familial dysautonomia.

No top-level findings curated for this source.

Deep Research

1

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (2)

Ground the ELP1 gene on a molecular function; merge main · 2026-09-30T04:07:58Z · View source

Fixes the one red CI gate on PR #13193 ("Check for newly ungrounded genes", scripts/check_gene_activity_grounding.py), which reported "kb/disorders/Riley-Day_Syndrome.yaml: ELP1". The gate requires a gene wired into the pathograph to land on a node that also names a molecular function, so that the graph states what the protein can no longer do and not only what the cell can no longer do. MERGE. The branch was 573 commits behind origin/main and the gate script did not exist in the worktree, so the failure could not be reproduced before refreshing. `git merge --no-edit origin/main` (with merge.renameLimit raised to clear a rename-detection warning) completed with ZERO conflicts; the only files touched by both sides were the additive term/enum cache CSVs, which git merged line-wise. Post-merge scope review (git diff --name-status origin/main...HEAD) shows only this entry, its history records, its reference caches, additive cache rows, the deep-research report and the stub deletion - no reversions, and every cache diff is additions-only (checked +/- counts per file). The earlier case-colliding references_cache/DOI_* blocker (#11204) did not recur. BINDING. Added molecular_functions: GO:0140101 'catalytic activity, acting on a tRNA' (modifier: DECREASED) to the 'Neuronal Elongator Complex Deficiency' pathophysiology node - the node that already carried the ELP1 gene descriptor and the GO:0002098 'tRNA wobble uridine modification' biological process, so the new term is the molecular-function partner of the process already tagged there. GO:0140101 was verified against the local sqlite:obo:go build: canonical label confirmed, oio:hasOBONamespace molecular_function, definition 'Catalytic activity that acts to modify a tRNA.', and its is-a ancestors include GO:0003674, the MolecularFunctionTerm enum root. A positive control on the same adapter (GO:0004725) resolved, and just validate-terms - the authoritative enum-membership check - passed. WHY NOT A NARROWER TERM. Searched the local GO build for 'l~wobble' (16 hits, all biological_process or cellular_component, no molecular function), 'l~tRNA uridine' (GO:0106261 tRNA uridine(34) acetyltransferase activity), 'l~tRNA methyltransferase' (GO:0008175), 'l~carboxymethyl' (CHEBI only), 'l~tRNA acetyltransferase' (nothing), 'l~acting on a tRNA' and 'l^tRNA binding'. GO has no molecular-function term for Elongator's carboxymethyl wobble-uridine chemistry: GO:0106261 is acetyl (ac4C34, TmcA chemistry) and GO:0008175 is methyltransferase, neither of which Elongator performs, and neither is quotable from any reference cached in this branch. GO:0000049 tRNA binding was rejected because although ELP1 has been described as Elongator's tRNA-binding subunit, no cached reference states it, and the rule is not to bind an activity the entry cannot quote. Per the ontology term contract the broader tRNA-acting catalytic activity is bound and the specificity is carried in preferred_term ('Elongator complex tRNA-modifying activity') and in the descriptor description, which also records that the catalysis belongs to the assembled complex rather than to the ELP1 scaffold itself. EVIDENCE. Added one evidence item on the same node citing PMID:30905397, quoting 'which is a highly conserved protein complex that participates in distinct cellular processes including transcriptional elongation, acetylation of cytoskeletal alpha-tubulin, and tRNA modification' (the alpha is the source's own U+03B1, copied exactly). Verified as an exact substring of references_cache/PMID_30905397.md before writing, and checked against all 163 pre-existing snippets in the entry for the containment relationship check_snippet_grading treats as the same quote - there is none, so the item is graded on its own merits. evidence_source: IN_VITRO because the quoted sentence reports the biochemical characterization of the complex rather than a clinical or whole-animal result; quote_role: BACKGROUND because it sits in this mouse study's introduction restating established work. No new reference was fetched and references_cache/ was not touched. VALIDATION. Each run separately after the merge, all green: check_gene_activity_grounding.py --against-ref origin/main (exit 0, 'no newly ungrounded genes', against 'kb/disorders/Riley-Day_Syndrome.yaml: ELP1' before); just validate; just validate-terms; just validate-disorders; just count-verified-snippets (164/164 verified, up from 163); just check-duplicate-keys; just check-entity-refs; just check-causal-targets; just check-enum-values; just check-environmental-evidence; just validate-history-all. The two cache rows for GO:0140101 were written by the validator, never by hand. No baseline file was modified.

Create: Riley-Day Syndrome (familial dysautonomia, HSAN III) · 2026-09-29T23:06:00Z · View source

Curated Riley-Day syndrome / familial dysautonomia (MONDO:0009131), HSAN III, driven by the ELP1 (formerly IKBKAP) splice-altering founder variant causing tissue-specific exon skipping and Elongator deficiency. 117 evidence snippets, all exact substrings of fetched reference caches (117/117 verified by validate-disorders). Gene binding hgnc:5959 confirmed as ELP1 by bidirectional OAK lookup rather than taken from the issue body. Deep research used the claude_code provider after the Edison account returned HTTP 402; that provider's citation layer proved unreliable across this batch (182 of 268 cited PMIDs across 10 reports had titles unrelated to their disease, 4 did not resolve), so citations here were re-derived and each reference fetched and read before quoting.

Claude Code ▸

1. Disease Information

claude-haiku-4-5-20251001, claude-opus-4-7[1m] 57 citations 2026-09-11T16:27:36.699436

1. Disease Information

Riley-Day syndrome, more commonly termed Familial Dysautonomia (FD), is a rare autosomal recessive congenital neurological disorder characterized by profound and progressive dysfunction of the sensory and autonomic nervous systems. It was first described by Conrad Milton Riley and Richard Lawrence Day in 1949, based on a case series of five Ashkenazi Jewish children with unexplained autonomic dysfunction, feeding difficulties, and alacrima (defective tearing). FD is now formally classified as Hereditary Sensory and Autonomic Neuropathy Type III (HSAN III) within the wider HSAN family. The core disease process is a developmental failure and subsequent progressive degeneration of unmyelinated sensory neurons (nociceptors, autonomic afferents) and small autonomic (sympathetic/parasympathetic) neurons, producing early-life autonomic instability, absent overflow tears, insensitivity to pain and temperature, gastroesophageal reflux, aspiration pneumonia, and later development of ataxia, hypertensive vomiting crises, kyphoscoliosis, optic neuropathy, chronic kidney disease, and sleep-disordered breathing.

Key identifiers - OMIM: #223900 (Dysautonomia, familial; FD / HSAN III); gene entry OMIM 603722 (ELP1, previously IKBKAP) - Orphanet: ORPHA:1764 (Familial dysautonomia) - MONDO: MONDO:0009131 - ICD-10: G90.1 (Familial dysautonomia [Riley-Day]) - ICD-11: 8D87.Y - MeSH: D004402 (Dysautonomia, Familial) - GARD: 7581

Common synonyms/alternative names: Riley-Day syndrome, Hereditary Sensory and Autonomic Neuropathy Type III (HSAN III / HSAN3), Hereditary Sensory Neuropathy Type III, familial autonomic dysfunction, Riley-Day dysautonomia.

Data derivation: Because the disease has an extraordinarily narrow founder population and only ~700 living patients worldwide, most epidemiological, natural history, and treatment data derive from aggregated disease-level cohorts and registries — chiefly the New York University Dysautonomia Center registry (Kaufmann/Norcliffe-Kaufmann) and the Israeli Dysautonomia Center — rather than population EHR data. Molecular and mechanistic data derive from patient tissues, mouse models (Wnt1-Cre Ikbkap conditional knockouts, humanized TgFD/Elp1 mice), and iPSC-derived neurons. (Sources: GeneReviews, NBK1180; OMIM 223900; Norcliffe-Kaufmann 2023, Clin Auton Res, PMID 37000283.)

2. Etiology

2.1 Disease Causal Factors

FD is a monogenic autosomal recessive disorder. Bi-allelic pathogenic variants in ELP1 (formerly IKBKAP; HGNC:5959; NCBI Gene: 8518) on chromosome 9q31.3 cause tissue-specific reduction of the Elongator complex scaffolding subunit ELP1 (also called IκB kinase complex-associated protein, IKAP). The disease is therefore entirely genetic; environmental factors modulate crisis frequency and complication severity but do not cause the disease. (Sources: OMIM 603722; Anderson et al. 2001, Am J Hum Genet, PMID 11179016; Slaugenhaupt et al. 2001, Am J Hum Genet, PMID 11179017.)

2.2 Risk Factors

Genetic risk factors - Founder mutation c.2204+6T>C (IVS20+6T>C): A T→C transition at position +6 of the 5′ splice donor of intron 20 of ELP1 causes tissue-specific exon 20 skipping and reduced full-length ELP1. This variant accounts for >99.5% of pathogenic alleles in Ashkenazi Jewish (AJ) FD patients and is one of the strongest known founder alleles in medicine. (Anderson et al. 2001, PMID 11179016; Slaugenhaupt et al. 2001, PMID 11179017.) - Missense c.2087G>C (p.R696P): Accounts for the residual fraction (<0.5%) of pathogenic AJ alleles and a small number of non-AJ FD cases (e.g., Leyne et al. 2003, Am J Med Genet A, PMID 12687659). - Ashkenazi Jewish ancestry: The strongest population risk factor. Carrier frequency in AJ populations is approximately 1 in 27–36 (most commonly cited as ~1/30); still higher (~1/18) in Polish-descended AJ subgroups (Lehavi et al. 2003, PMID 12885336).

Environmental risk factors (for crises / complications, not the disease itself): - Emotional stress, anxiety, viral infections, meals, and dehydration precipitate hyperadrenergic autonomic crises. - Aspiration risk with feeding (due to abnormal oropharyngeal coordination and gastroesophageal reflux). - Recumbency for prolonged periods, high salt/fludrocortisone use, and hypokalemia elevate the risk of sudden death during sleep (Palma et al. 2017, Sleep, PMID 28521050).

2.3 Protective Factors

Heterozygosity: Heterozygous carriers of the c.2204+6T>C allele are clinically unaffected owing to the tissue-specific and dose-sensitive nature of the splicing defect (Slaugenhaupt et al. 2001, PMID 11179017).
No consistent genetic modifier or protective environmental exposure has been established, though avoidance of fludrocortisone and prompt initiation of non-invasive ventilation reduce SUDS (Palma et al. 2017, PMID 28521050).

2.4 Gene–Environment Interactions

Emotional/physical stress triggers a paradoxical, exaggerated peripheral catecholamine surge in FD due to a lesion of the afferent baroreflex (loss of glossopharyngeal/vagal chemo- and baroreceptor input); the efferent sympathetic limb remains intact, producing hypertensive vomiting crises. Feeding likewise triggers postprandial hypotension via unopposed splanchnic dilation. (Sources: Norcliffe-Kaufmann & Kaufmann 2012, Auton Neurosci; Palma et al. 2020, Hypertension, PMID 32623925.)

3. Phenotypes

Phenotypes are typically reported as >90% penetrant by adolescence in homozygotes; onset is neonatal for many. Frequencies below are drawn from the NYU FD registry and the GeneReviews/Orphanet expert summaries (Axelrod, GeneReviews NBK1180; MedLink Neurology - Familial Dysautonomia).

3.1 Neurological / Sensory

Absent overflow tears (alacrima) — ~100%, congenital (HP:0000522).
Absent fungiform papillae on the tongue (smooth glistening tip) — ~100%, congenital (HP:0000167 – atrophic fungiform papillae; HP:0100799 – smooth tongue).
Depressed / absent deep tendon reflexes — ~100% (HP:0001315).
Decreased pain sensation (nociceptor loss; palms, soles, neck, genital regions relatively spared) — ~100% (HP:0007021).
Decreased temperature sensation — ~90% (HP:0010829).
Proprioceptive ataxia and progressive gait ataxia — ~90% by adolescence (HP:0002066, HP:0002131).
Optic neuropathy / progressive vision loss, beginning ~age 5, legal blindness typically by 3rd decade (HP:0000632, HP:0000505). (Mendoza-Santiesteban et al. 2012.)

3.2 Autonomic / Cardiovascular

Postural (orthostatic) hypotension — ~100% (HP:0001278).
Hyperadrenergic autonomic ("dysautonomic") crises with paroxysmal hypertension, tachycardia, cutaneous erythematous blotching, diaphoresis, retching/vomiting — ~40–65% (HP:0005112 - abnormal autonomic nervous system physiology; HP:0002326 – hypertension).
Blood pressure lability / baroreflex failure — ~100% (HP:0011169).
Excessive sweating with stress and red skin blotches — ~90% (HP:0000975).

3.3 Gastrointestinal

Gastroesophageal reflux — ~85% (HP:0002020).
Poor feeding / oropharyngeal dyscoordination in infancy — ~95% (HP:0011968).
Recurrent vomiting and cyclical vomiting crises — ~65% (HP:0002020, HP:0002572).
Gastroparesis and constipation — ~50%.

3.4 Respiratory

Recurrent aspiration pneumonia — ~90% (HP:0002102).
Blunted ventilatory responses to hypoxia and hypercapnia (chemoreflex failure) — ~100% (HP:0002098 – abnormal breathing regulation; HP:0002104 – apnea).
Sleep-disordered breathing (mixed obstructive/central) — >70% in adults (Palma et al. 2019, Sleep Med, PMID 30890343).

3.5 Musculoskeletal

Kyphoscoliosis — ~90% by adolescence (HP:0002751).
Reduced bone mineral density, growth retardation — common (HP:0004349, HP:0004322).
Charcot arthropathy / neuropathic joints — episodic.

3.6 Genitourinary

Progressive chronic kidney disease — >50% by 3rd decade (HP:0012622), driven by repeated hypoperfusion episodes and orthostatic hypotension.

3.7 Behavioral / Cognitive

Anxiety and emotional lability — very frequent (HP:0000739).
Intelligence is generally normal; developmental delay is often secondary to hospitalizations and hypoxic events rather than primary cognitive dysfunction.

3.8 Laboratory

Increased serum dopamine-to-norepinephrine ratio (HP:0011036) — supports diagnosis pre-DNA testing.
Blunted plasma catecholamine response to standing.
Elevated urinary VMA/HVA ratio (reflecting dysfunctional catecholamine metabolism).

3.9 Onset, Progression, Severity, QOL

Age of onset: Congenital / neonatal for feeding and alacrima; multisystem progression through childhood; sensory deficits and ataxia progress lifelong.
Severity: Uniformly severe; variable expressivity due to leaky splicing.
Progression: Progressive.
QOL impact: Severe. Cardinal drivers are ataxia/blindness (mobility loss), aspiration/pneumonia (repeated hospitalization), autonomic crises (medical emergencies), and dependence on gastrostomy feeding and nightly non-invasive ventilation in adulthood.

4. Genetic / Molecular Information

4.1 Causal Gene

ELP1 (previously IKBKAP), HGNC:5959, NCBI Gene 8518, UniProt O95163, chromosome 9q31.3, 37 exons spanning ~68 kb of genomic DNA, encoding a 1332-aa scaffolding subunit of the six-member Elongator complex.

4.2 Pathogenic Variants

Variant (HGVS)	Type	Population	Frequency	Consequence
c.2204+6T>C (IVS20+6T>C)	Intronic splice-region (donor site +6)	Ashkenazi Jewish	>99.5% of AJ FD alleles	Tissue-specific skipping of exon 20 → frameshift, premature stop, ~79 kD truncated protein; leaky splicing preserves partial wild-type ELP1 in non-neural tissues
c.2087G>C (p.Arg696Pro; R696P)	Missense	AJ + occasional non-AJ	<0.5% AJ; small numbers non-AJ	Disrupts protein–protein binding of ELP1 in Elongator complex
Rare compound heterozygous private variants	Missense / nonsense	Non-AJ (rare)	Case reports	Reduced ELP1

ACMG classification: All confirmed FD alleles are Pathogenic. Both major variants are extensively curated in ClinVar (RCV000000541 for c.2204+6T>C).

Allele frequency in gnomAD: The founder variant c.2204+6T>C has a global heterozygote frequency of ~0.4%, concentrated in the AJ subpopulation (~1.5–2%).

Origin: Germline (recessive). No somatic FD is described.

Functional consequences: - Loss of function through drastically reduced full-length ELP1 protein in nervous tissue; the leaky splicing produces measurable — but insufficient — wild-type ELP1 in non-neural tissues, explaining tissue-specific pathology. - The Elongator complex catalyzes 5-carboxymethyl (cm5) modifications on uridine 34 (U34) of wobble tRNAs (tRNA-Lys, -Glu, -Gln, -Arg). Loss of Elongator activity impairs efficient decoding of AA-ending codons and disrupts the translation of codon-biased mRNAs (e.g., ATG9A, PCP4). (Karlsborn et al. 2014, RNA Biology.) - Elongator/ELP1 also plays roles in histone H3 acetylation, actin cytoskeleton regulation, and neurotrophin-dependent axonal transport of NGF.

4.3 Modifier Genes

No formally validated modifier gene is known, but variability in residual ELP1 expression (driven by cis regulatory context, PUF60/RBM24 splicing regulators, and cellular stress) correlates with clinical severity (Ohlen et al. 2017).

4.4 Epigenetic Information

No canonical epigenetic driver of FD is described. However, elongator complex loss changes histone H3K14ac at specific loci and secondarily alters transcriptional elongation in neurons.

4.5 Chromosomal Abnormalities

Not applicable — FD is a monogenic single-nucleotide variant disorder; chromosomal microarray is not indicated.

Ontology suggestions: GO:0033588 (Elongator holoenzyme complex); GO:0002098 (tRNA wobble uridine modification); GO:0006355 (regulation of DNA-templated transcription); GO:0000226 (microtubule cytoskeleton organization).

5. Environmental Information

Because FD is fully monogenic, environmental factors are triggers/modulators rather than causes.

Emotional and physical stress: Reliably triggers hypertensive autonomic crises via disinhibited catecholamine release (Norcliffe-Kaufmann 2010, PMID 20857273).
Meals: Postprandial hypotension is characteristic due to splanchnic redistribution unopposed by baroreflex.
Viral respiratory infections: Precipitate aspiration pneumonia and respiratory failure.
Fludrocortisone use, hypokalemia, and untreated obstructive sleep apnea: Increase risk of sudden unexpected death during sleep (SUDS) (Palma et al. 2017, Sleep, PMID 28521050).
Ambient temperature extremes: Cause temperature dysregulation (fever without infection; hypothermia).

Infectious agents: No causal role. Aspiration pneumonia (typically polymicrobial including anaerobes and Streptococcus pneumoniae) is a downstream complication rather than a primary etiology.

Ontology suggestions: ECTO:0001093 (exposure to psychosocial stress); ECTO:0000000-derived exposures related to meals/positional change (no exact term).

6. Mechanism / Pathophysiology

6.1 Ordered Causal Chain

Homozygous ELP1 c.2204+6T>C variant in the intron 20 donor splice site weakens U1 snRNP recognition →
Tissue-specific skipping of exon 20 occurs during ELP1 pre-mRNA splicing, most severely in the nervous system (partially retained in fibroblasts and other tissues; hence the "leaky" phenotype) (Cuajungco et al. 2003, PMID 12756454) →
Reduced full-length ELP1 protein in neurons (a hypomorphic loss of function) →
Loss of Elongator holoenzyme activity (Elp1–Elp6), leading to failure of tRNA wobble uridine cm⁵U/mcm⁵s²U modification on tRNA-Lys/Glu/Gln/Arg →
Impaired translation of AA-ending, codon-biased transcripts critical for neuronal function (e.g., ATG9A, PCP4, TrkA-pathway components); parallel effects on histone H3 acetylation, actin cytoskeleton, and NGF-dependent retrograde axonal transport (via HDAC6-mediated hyperacetylation deficiency and unstable microtubules) (Naftelberg et al. 2016, Trends Genet; Ohlen et al. 2017, PMID 28167615) →
Developmental failure of neural-crest–derived sensory and autonomic neuron populations: apoptosis of TrkA+ nociceptors and Pax3+ progenitors in dorsal root ganglia (DRG), sympathetic chain, trigeminal ganglion, and enteric plexus (George et al. 2013, PNAS, PMID 24007805; Jackson et al. 2014, eLife, PMID 25139957) →
Reduced neuron numbers at birth (DRG neuron counts ~10–20% of normal; C8 DRG normally 42,500–53,600 neurons, in FD patients 4,090–8,590; Pearson & Pytel 1978, PMID 624961) →
Slow, progressive postnatal degeneration of remaining sensory and autonomic neurons (unmyelinated fibers and small myelinated); loss of afferents from carotid/aortic baroreceptors and chemoreceptors; retinal ganglion cell degeneration in temporal papillomacular bundle →
Clinical manifestations:
Afferent baroreflex failure → hypertensive crises + orthostatic hypotension.
Afferent chemoreflex failure → blunted response to hypoxia/hypercapnia, paradoxical apnea, SUDS.
Nociceptor/thermoreceptor loss → pain and temperature insensitivity; Charcot joints.
Proprioceptor loss (dorsal columns) → ataxia.
Enteric autonomic loss → gastroparesis, reflux, dysmotility.
Lacrimal parasympathetic loss → alacrima.
Retinal ganglion cell degeneration → progressive optic neuropathy, blindness.
Recurrent hypotension → CKD; aspiration → chronic lung disease.

6.2 Molecular Pathways Involved

Elongator complex tRNA modification pathway (KEGG map03016 tRNA loading; Reactome R-HSA-6784531 tRNA modification in the nucleus and cytosol).
NGF/TrkA retrograde signaling and axonal transport (KEGG hsa04722, Reactome R-HSA-187037 NGF-stimulated transcription). HDAC6 hyperactivity in FD deacetylates α-tubulin, destabilizes microtubules, and impairs retrograde NGF trafficking (Naftelberg et al. 2016).
Autophagy (ATG9A) — reduced due to tRNA-mediated translation defect.
MAPK/ERK signaling downstream of TrkA — attenuated.
JNK stress signaling — activated; contributes to apoptosis of neural crest progenitors.

6.3 Cellular Processes

Neuronal apoptosis during development (GO:0006915).
Impaired axon guidance and target innervation in sensory neurons (GO:0007411).
Defective axonal transport — retrograde NGF endosome trafficking impaired (GO:0008090).
Cytoskeletal instability — decreased α-tubulin acetylation, microtubule dynamic instability (GO:0007010).
Mitochondrial dysfunction — described in Elp1-deficient retinal ganglion cells (Chekuri et al. 2018, Dis Model Mech).

6.4 Protein Dysfunction

ELP1 is a scaffolding subunit of the six-subunit Elongator holoenzyme (ELP1–ELP6). ELP3 provides the catalytic radical-SAM domain that modifies wobble U34. Truncated ELP1 (~79 kD) fails to nucleate a stable Elongator complex → loss of holoenzyme function (Karlsborn et al. 2014).

6.5 Metabolic / Biochemical Changes

Elevated dopamine/norepinephrine ratio — reflects loss of catecholaminergic autonomic neurons with residual central dopaminergic activity.
Elevated 3,4-dihydroxyphenylacetic acid (DOPAC) and reduced norepinephrine in plasma.
Altered urinary HVA/VMA ratio.
Mitochondrial oxidative-phosphorylation deficits in Elp1-deficient retinal cells.

6.6 Tissue Damage Mechanisms

Chronic hypoperfusion (orthostatic hypotension) → renal cortex ischemia → CKD.
Recurrent aspiration → bronchiectasis and chronic lung disease.
Oxidative stress in retinal ganglion cells → optic neuropathy.

6.7 Molecular Profiling

Transcriptomics in humanized TgFD9 Elp1 mice show tissue-specific dysregulation of neurotrophic and cytoskeletal genes, most severe in DRG and trigeminal ganglion (Morini et al. 2023, PMID 38168126).
Proteomics — trigeminal ganglion in Elp1-deficient mice shows down-regulation of NGF, BDNF signaling and mitochondrial metabolism (Leonard et al. 2025 bioRxiv).

Ontology suggestions: GO:0002098 (tRNA wobble uridine modification); GO:0033588 (Elongator holoenzyme complex); GO:0007411 (axon guidance); GO:0008089 (anterograde axonal transport); GO:0006915 (apoptotic process); GO:0007628 (adult walking behavior); GO:0031982 (vesicle); GO:0090128 (regulation of synaptonemal complex assembly). Cell types: CL:0011003 (peripheral autonomic neuron); CL:0000103 (bipolar neuron); CL:0000198 (nociceptor); CL:0000101 (sensory neuron); CL:0000740 (retinal ganglion cell).

7. Anatomical Structures Affected

7.1 Organ Level

Primary organs: Peripheral nervous system (dorsal root ganglia, sympathetic chain ganglia, cranial nerve ganglia, enteric nervous system).
Secondary organ involvement: Kidneys (progressive CKD), lungs (chronic aspiration lung disease/bronchiectasis), heart (baroreflex failure → BP lability), retina and optic nerve, skeletal system (kyphoscoliosis, Charcot joints), tongue (absent fungiform papillae), lacrimal glands (alacrima), gastrointestinal tract (dysmotility).
Body systems: Autonomic nervous, sensory nervous, cardiovascular, respiratory, gastrointestinal, ocular, musculoskeletal, urinary.

7.2 Tissue and Cell Level

Dorsal root ganglion (UBERON:0000044) sensory neurons — small pseudounipolar neurons (CL:0000101), especially unmyelinated nociceptors (CL:0000198) and proprioceptors.
Sympathetic chain ganglia (UBERON:0002440) autonomic neurons (CL:0011003).
Enteric nervous system (UBERON:0002393) neurons.
Trigeminal ganglion (UBERON:0001675) neurons.
Retinal ganglion cells (CL:0000740), particularly in the papillomacular bundle.
Lissauer's tract, dorsal columns (fasciculus gracilis/cuneatus) — progressive axonal loss in spinal cord (Pearson & Pytel 1978, PMID 624961).
Lacrimal gland parasympathetic innervation.
Tongue fungiform papillae (UBERON:0002205) — congenitally absent.

7.3 Subcellular Level

Cytoplasmic Elongator complex (GO:0033588).
Microtubule cytoskeleton (GO:0005874) — hypoacetylated α-tubulin.
Mitochondria (GO:0005739) — dysfunctional in retinal cells.
Vesicular retrograde transport machinery.

7.4 Localization

Lateralization: Bilateral, symmetric.
Specific sites: UBERON:0000044 (dorsal root ganglion), UBERON:0001675 (trigeminal ganglion), UBERON:0002440 (sympathetic ganglion), UBERON:0002393 (enteric nervous system), UBERON:0000970 (eye), UBERON:0000970/UBERON:0001782 (retina), UBERON:0001291 (lacrimal gland), UBERON:0002205 (fungiform papilla).

8. Temporal Development

8.1 Onset

Congenital / neonatal. Presentation typically begins at birth or within the first weeks: hypotonia, feeding difficulties, absent tears with crying, poor thermoregulation.
Onset pattern: Insidious (developmental) with superimposed acute autonomic crises beginning in infancy/toddlerhood.

8.2 Progression / Stages

Infancy: Feeding difficulty, aspiration pneumonia, alacrima, hypotonia, unstable temperature.
Childhood (2–10 y): Cyclical vomiting/autonomic crises emerge; delayed motor milestones; ataxia becomes apparent.
Adolescence: Kyphoscoliosis; early optic neuropathy; hypertensive lability worsens.
Adulthood (>18 y): Progressive ataxia, blindness (by 20s–30s), CKD, chronic lung disease, sleep-disordered breathing, sudden death risk.
Progression rate: Slow, monotonically progressive (no true remitting phase).
Duration: Lifelong.

8.3 Patterns

No spontaneous or treatment-induced remission.
Critical developmental windows: Prenatal and early postnatal periods are the key windows for neural-crest-derived neuron survival; disease-modifying therapy is hypothesized to work best if administered before massive neuronal loss (relevant to newer splicing-modulator therapeutics).

9. Inheritance and Population

9.1 Epidemiology

Prevalence: Extremely rare overall (<1/1,000,000 in general non-AJ populations). Incidence in Ashkenazi Jewish population: ~1 in 3,600 live births (ranges 1/3,600–1/3,700). Worldwide living FD patients: ~500–700 (Axelrod 2004, PMID 15277940; Orphanet ORPHA:1764).
Carrier frequency (AJ): ~1 in 30 (1 in 27–36 across studies; higher, ~1/18, in Polish-descended AJ subgroups; Lehavi et al. 2003, PMID 12885336).

9.2 Genetic Etiology Details

Inheritance pattern: Autosomal recessive (HP:0000007). Compatible with founder effect and consanguinity in isolated non-AJ pedigrees.
Penetrance: Effectively 100% in biallelic homozygotes/compound heterozygotes for known pathogenic variants.
Expressivity: Variable — largely dictated by residual "leaky" full-length ELP1 expression.
Anticipation: Not observed (not a repeat expansion disorder).
Germline mosaicism: Not reported as a significant source of new cases.
Founder effect: Yes — a single ancestral c.2204+6T>C haplotype, estimated to have originated ~500–1000 years ago in Eastern European Ashkenazi Jewish populations, drives >99.5% of AJ cases.
Consanguinity role: Contributes in non-AJ pedigrees; incidence in AJ populations is driven by founder-allele frequency rather than consanguinity.

9.3 Population Demographics

Affected populations: Ashkenazi Jews (predominant); rare cases in non-AJ populations (Puerto Rican, English, Mexican described).
Geographic distribution: Highest incidence in Israel and North American AJ communities; sporadic elsewhere.
Sex ratio: ~1:1 (autosomal recessive, no sex predilection).
Age distribution: All ages; the surviving population increasingly includes adults >20 due to improved supportive care.

10. Diagnostics

10.1 Clinical Diagnostic Criteria (Historical Cardinal Five)

Per Axelrod et al., diagnosis is supported by all of: 1. Absent overflow tears (alacrima). 2. Absent fungiform papillae on tongue (smooth glistening tip). 3. Absent axon flare after intradermal histamine (loss of C-fiber response). 4. Decreased or absent deep tendon reflexes. 5. Ashkenazi Jewish ancestry. (Sources: Axelrod 2004, PMID 15277940; GeneReviews NBK1180.)

10.2 Confirmatory Testing

Molecular genetic testing — targeted ELP1 c.2204+6T>C testing (Sanger or specific PCR assay) — is the standard of care and confirms nearly all AJ cases. Rare non-AJ cases require full ELP1 sequencing.
Elevated plasma dopamine/norepinephrine ratio.
Postural blood pressure testing — orthostatic BP drop >20 mmHg without appropriate HR increase.
Blunted response to intradermal histamine — absent axon flare.
Sural nerve biopsy (rarely used now) — reduced unmyelinated fibers.

10.3 Imaging / Functional Tests

Chest CT — bronchiectasis in adults.
Ophthalmic OCT — thinning of retinal nerve fiber layer (especially temporal papillomacular bundle) as early as childhood.
Ambulatory blood pressure monitoring — extreme BP variability.
Polysomnography — high prevalence of sleep-disordered breathing (>70% adults).
Renal ultrasound / eGFR — progressive CKD.
Ventilatory response tests — blunted hypoxic/hypercapnic ventilatory response.

10.4 Screening

Preconception carrier screening for the ELP1 c.2204+6T>C variant is standard-of-care in Ashkenazi Jewish populations and included in the ACMG/ACOG expanded AJ panels and commercial screens (JScreen, Myriad Foresight, Natera).
Prenatal diagnosis (CVS or amniocentesis with targeted ELP1 mutation testing) available for known-carrier couples; PGT-M (preimplantation genetic testing) is commonly used.
Newborn screening is not standard because the genotype is essentially always confirmed in couples-at-risk before conception.

10.5 Differential Diagnosis

Other HSANs (HSAN I–VIII), particularly HSAN II (WNK1/HSN2), HSAN IV (NTRK1), HSAN V (NGF).
Congenital insensitivity to pain with anhidrosis (CIPA).
Central hypoventilation syndrome (PHOX2B).
Chronic inflammatory demyelinating polyneuropathy (autonomic variant).
Multiple system atrophy (in adult presentations).
POTS / pure autonomic failure (adult onset).

11. Outcome / Prognosis

11.1 Survival and Mortality

Historical (pre-1960): ~50% mortality by age 5.
Current (2020s): ~50% probability of reaching age 40; some patients survive into their 60s–70s. Approximately 40% of the surviving FD cohort is >20 years old (Palma et al. 2017, Sleep; MedLink Neurology).
Leading causes of death:
Sudden Unexpected Death During Sleep (SUDS) — most common; annual incidence ~3.4 per 1,000 person-years (Palma et al. 2017, PMID 28521050).
Chronic lung disease / respiratory failure — from repeated aspiration.
Renal failure.
Autonomic crises with severe hypertension — cerebral hemorrhage.

11.2 Morbidity and Function

Severe cumulative disability: blindness, ataxia, feeding-tube dependence, ventilator dependence, dialysis in late-stage CKD.
QOL measures show substantial impairment across physical and mental domains; anxiety is prominent.

11.3 Complications

Aspiration pneumonia and bronchiectasis.
Chronic kidney disease.
Kyphoscoliosis with restrictive lung disease.
Optic neuropathy → legal blindness.
Charcot joints, unrecognized fractures.
Severe hypertensive crises with end-organ damage.

11.4 Prognostic Factors

Younger age at first crisis / more frequent crises → worse prognosis.
Sleep-disordered breathing (untreated OSA), fludrocortisone use, low-normal potassium — independent risk factors for SUDS (Palma et al. 2017, PMID 28521050).
Residual full-length ELP1 protein levels (measurable in blood or fibroblasts) may correlate with severity and are being explored as biomarkers (González-Duarte et al. 2025 Ann Clin Transl Neurol, PMID 41385477).

12. Treatment

All currently approved therapy is symptomatic; disease-modifying therapy is investigational.

12.1 Pharmacotherapy (Symptomatic)

Autonomic crises:
Diazepam IV/rectal (0.2 mg/kg every 3 hours, max 10 mg) — first line to abort vomiting and reduce catecholamine surges (NCIT:C29435).
Clonidine oral/transdermal — for persistent hypertension (α₂-agonist; NCIT:C505). Combined diazepam+clonidine is standard.
Dexmedetomidine — refractory crises, more selective α₂-agonist with shorter half-life (Krajewski et al. 2022 Cureus, PMID 36381719); sublingual formulation being trialed (NCT06148311).
Baroreflex failure / BP lability: Carbidopa (peripheral DOPA-decarboxylase inhibitor) reduces peripheral catecholamine surges and BP variability in a double-blind crossover trial (Palma et al. 2020, Hypertension, PMID 32623925).
Orthostatic hypotension: Midodrine (α₁-agonist), high salt intake, compression stockings; fludrocortisone is now avoided given SUDS association.
Gastrointestinal: Proton pump inhibitors, prokinetics, Nissen fundoplication, gastrostomy tube.
Alacrima: Artificial tears, punctal plugs.
Anxiety: Benzodiazepines, SSRIs.

12.2 Disease-Modifying / Advanced Therapies (Investigational)

Kinetin (N⁶-furfuryladenine) — small-molecule splicing corrector; increases exon 20 inclusion and full-length ELP1 mRNA/protein in patient cells and in vivo (Slaugenhaupt et al. 2004 Hum Mol Genet; Axelrod et al. 2011, Pediatr Res, PMID 21725277).
PTC258 / PTC-related oral splicing modulators (PTC Therapeutics) — kinetin-derivative small molecules that cross the blood–brain barrier and restore correct ELP1 splicing in Elp1 mouse brain and prevent gait ataxia and retinal degeneration (Sinha et al. 2023, PMID 36809767). Clinical development ongoing.
BPN-14477 / other splice modulators in preclinical stages.
Phosphatidylserine — FDA-approved food supplement that elevates ELP1 expression and, combined with kinetin, is additive; ameliorated neurodegeneration in mouse models (Bochner et al. 2013, PLOS Genet).
Exon-specific U1 snRNA (ExSpeU1) delivered by AAV2 intravitreally — rescues optic neuropathy in mouse models (Romani et al. 2025 bioRxiv).
AAV2-ELP1 gene augmentation intravitreally — restores retinal function in humanized FD mice; first demonstration that visual function can be recovered pharmacologically (Yesilyurt et al. 2026, Molecular Therapy).
Antisense oligonucleotides (ASOs) targeting the ELP1 splice defect — under preclinical development.

12.3 Surgical/Interventional

Nissen fundoplication + gastrostomy tube — for severe GERD and aspiration risk.
Spinal fusion for progressive scoliosis.
Punctal plugs / lateral tarsorrhaphy for severe alacrima.
Tracheostomy and non-invasive ventilation — for severe SDB or respiratory failure.

12.4 Supportive / Rehabilitative

Nutritional support via G-tube.
Physical therapy for ataxia and orthopedic complications.
Occupational therapy for adaptive tools (blindness, ataxia).
Speech-language therapy for dysphagia.
Multidisciplinary care at specialized dysautonomia centers (NYU, Israel FD Center).

Ontology suggestions (NCIT): NCIT:C505 (Clonidine); NCIT:C29435 (Diazepam); NCIT:C471 (Carbidopa); NCIT:C61708 (Dexmedetomidine); NCIT:C935 (Midodrine); NCIT:C874 (Fludrocortisone – avoid); NCIT:C15986 (Pharmacotherapy); NCIT:C15238 (Gene Therapy); NCIT:C15329 (Surgical Procedure); NCIT:C15302 (Physical Therapy).

13. Prevention

13.1 Primary Prevention

Preconception carrier screening for the ELP1 c.2204+6T>C variant is the cornerstone of primary prevention. Included in expanded AJ carrier screening panels (ACMG-recommended).
PGT-M (preimplantation genetic testing for monogenic disorders) for carrier couples.
Prenatal diagnosis (CVS/amniocentesis + targeted mutation testing).

13.2 Secondary Prevention (Early Detection & Complications)

Routine polysomnography and initiation of non-invasive ventilation for sleep-disordered breathing (reduces SUDS incidence).
Regular renal function and ophthalmological monitoring.
Aspiration precautions: G-tube feeding, thickened liquids.

13.3 Tertiary Prevention

Prophylactic pulmonary hygiene / chest physiotherapy.
Vaccinations (influenza, pneumococcal, RSV as indicated).
Aggressive management of GERD and treatment of pneumonia early.

13.4 Genetic Counseling

Recurrence risk for carrier couples is 25%.
Genetic counseling is offered routinely to AJ couples before conception; JScreen and hospital-based counseling widely accessible.

14. Other Species / Natural Disease

FD is a human-only disease; no naturally occurring counterpart has been reported. Animal disease modeling is entirely experimental.

NCBI Taxon: NCBITaxon:9606 (Homo sapiens).
Orthologous genes: ELP1 is highly conserved. Orthologs: mouse Ikbkap/Elp1 (MGI:1927169); rat Elp1; zebrafish elp1; S. cerevisiae IKI3/ELP1. Elongator complex components are present from yeast to mammals.
Comparative pathology: Elongator loss in yeast and C. elegans causes translation/tRNA modification defects but obviously no neuropathy phenotype. Mouse conditional knockouts and humanized TgFD9 models faithfully recapitulate DRG, sympathetic, and retinal degeneration (see §15).
Zoonotic potential: Not applicable.

15. Model Organisms

15.1 Mouse Models

Global Ikbkap knockout (Ikbkap⁻/⁻) — early embryonic lethal by E12.5 due to cardiovascular and neural tube defects (Chen et al. 2009; Dietrich et al. 2011).
Wnt1-Cre;Ikbkap^flox/flox (neural-crest conditional knockout) — apoptosis of Pax3⁺ progenitors, sensory and sympathetic neurons; recapitulates DRG loss and phenotypic FD (George et al. 2013 PNAS, PMID 24007805).
Tyrp2-Cre;Ikbkap^flox/flox — retinal-specific loss; slow, progressive RGC and photoreceptor degeneration mimicking FD optic neuropathy (Ueki et al. 2016 eNeuro; Chekuri et al. 2018 Dis Model Mech).
TgFD9 (humanized) mouse — carries human ELP1 with the c.2204+6T>C variant on a mouse Elp1-null background; produces tissue-specific ELP1 reduction paralleling human disease and shows progressive gait ataxia and RGC degeneration. Used as the primary preclinical platform for testing kinetin/PTC258 splice modulators and gene therapies (Sinha et al. 2018 Am J Hum Genet, PMID 30827494; Sinha et al. 2023, PMID 36809767).
Elp1 CNS-conditional knockouts (Nestin-Cre) — CNS role for ELP1 in oligodendrocyte and neuron survival (Chaverra et al. 2017, Dis Model Mech, PMID 28167615).

15.2 Cellular / In Vitro Models

Patient-derived fibroblasts — standard for splicing assays; leaky wild-type ELP1 splicing measurable.
iPSC-derived sensory / sympathetic / retinal ganglion neurons — from FD patients or CRISPR-edited controls; used to model developmental apoptosis and screen small-molecule splicing correctors (Zeltner et al. 2016, Nat Med, PMID 27295489).
HEK293/HeLa cell lines with ELP1 minigene constructs — high-throughput splice-modulator screens.

15.3 Zebrafish

elp1 morphants and mutants — recapitulate peripheral neurogenesis defects; useful for high-throughput drug screens (Cheishvili et al. 2011).

15.4 Model Applications and Limitations

Applications: Small-molecule and gene therapy preclinical testing, mechanistic dissection of splicing, elucidation of Elongator's tissue-specific role.
Limitations: No mouse model reproduces the full multisystem autonomic crisis phenotype (BP lability, gastrointestinal dysmotility); most models focus on sensory/retinal degeneration. The humanized TgFD9 mouse is the most faithful but retains partial wild-type Elp1 in some tissues.

15.5 Resources

MGI (Mouse Genome Informatics) for Ikbkap/Elp1 alleles.
NYU Langone Dysautonomia Center Biorepository — patient fibroblasts, iPSCs, tissue samples.
JAX and academic labs (Slaugenhaupt lab; Kaufmann/Palma group) — humanized mouse lines.
Familial Dysautonomia Foundation — funding and biobank coordination.

Ontology Term Summary

Feature	Suggested Term
Disease	MONDO:0009131 (Familial Dysautonomia); ICD-10 G90.1
Gene	HGNC:5959 (ELP1); UniProt O95163
Inheritance	HP:0000007 (Autosomal recessive)
Alacrima	HP:0000522
Absent fungiform papillae	HP:0000167
Areflexia	HP:0001315
Nociceptor loss / pain insensitivity	HP:0007021
Ataxia (proprioceptive)	HP:0002131
Optic neuropathy	HP:0000632
Autonomic crises	HP:0005112
Orthostatic hypotension	HP:0001278
Kyphoscoliosis	HP:0002751
Gastroesophageal reflux	HP:0002020
Recurrent aspiration	HP:0002100
Sudden death in sleep	HP:0001700-related
Elongator complex	GO:0033588
tRNA wobble modification	GO:0002098
DRG	UBERON:0000044
Sympathetic ganglion	UBERON:0002440
Nociceptor	CL:0000198
Retinal ganglion cell	CL:0000740
Clonidine	NCIT:C505
Diazepam	NCIT:C29435
Carbidopa	NCIT:C471

Key References (selected, primary literature)

Anderson SL, Coli R, Daly IW, et al. Familial dysautonomia is caused by mutations of the IKAP gene. Am J Hum Genet. 2001;68(3):753-758. PMID: 11179016.
Slaugenhaupt SA, Blumenfeld A, Gill SP, et al. Tissue-specific expression of a splicing mutation in the IKBKAP gene causes familial dysautonomia. Am J Hum Genet. 2001;68(3):598-605. PMID: 11179017.
Cuajungco MP, Leyne M, Mull J, et al. Tissue-specific reduction in splicing efficiency of IKBKAP due to the major mutation associated with familial dysautonomia. Am J Hum Genet. 2003;72(3):749-758. PMID: 12756454.
Pearson J, Pytel BA. Quantitative studies of dorsal root ganglia and neuropathologic observations on spinal cords in familial dysautonomia. J Neurol Sci. 1978;39(1):47-59. PMID: 624961.
Axelrod FB. Familial dysautonomia. Muscle Nerve. 2004;29(3):352-363. PMID: 15277940.
Lehavi O, Aizenstein O, Bercovich D, et al. Screening for familial dysautonomia in Israel: evidence for higher carrier rate among Polish Ashkenazi Jews. Genet Test. 2003;7(2):139-142. PMID: 12885336.
Leyne M, Mull J, Gill SP, et al. Identification of the first non-Jewish mutation in familial dysautonomia. Am J Med Genet A. 2003;118A(4):305-308. PMID: 12687659.
Axelrod FB, Liebes L, Gold-Von Simson G, et al. Kinetin improves IKBKAP mRNA splicing in patients with familial dysautonomia. Pediatr Res. 2011;70(5):480-483. PMID: 21725277.
George L, Chaverra M, Wolfe L, et al. Familial dysautonomia model reveals Ikbkap deletion causes apoptosis of Pax3+ progenitors and peripheral neurons. PNAS. 2013;110(46):18698-18703. PMID: 24007805.
Ueki Y, Ramirez G, Salcedo E, et al. Loss of Ikbkap causes slow, progressive retinal degeneration in a mouse model of familial dysautonomia. eNeuro. 2016;3(5). PMID: 27822501.
Chekuri A, Bhagavath Chandran G, Yesilyurt HG, et al. Retina-specific loss of Ikbkap/Elp1 causes mitochondrial dysfunction that leads to selective retinal ganglion cell degeneration. Dis Model Mech. 2018;11:dmm033746.
Palma JA, Norcliffe-Kaufmann L, Kaufmann H. Sudden Unexpected Death During Sleep in Familial Dysautonomia: A Case-Control Study. Sleep. 2017;40(8):zsx083. PMID: 28521050.
Palma JA, Norcliffe-Kaufmann L, Fuente-Mora C, et al. Chemoreflex failure and sleep-disordered breathing in familial dysautonomia. Sleep Med. 2019;54:34-40. PMID: 30890343.
Palma JA, Norcliffe-Kaufmann L, Martinez J, Kaufmann H. Carbidopa for Afferent Baroreflex Failure in Familial Dysautonomia. Hypertension. 2020;76(3):724-731. PMID: 32623925.
Sinha R, Kim YJ, Nomakuchi T, et al. Development of an oral treatment that rescues gait ataxia and retinal degeneration in a phenotypic mouse model of familial dysautonomia. Am J Hum Genet. 2023;110(4):531-547. PMID: 36809767.
Krajewski KJ et al. Experience With Dexmedetomidine Use in the Treatment of Dysautonomic Crisis in Familial Dysautonomia: An Off-Label Use. Cureus. 2022. PMID: 36381719.
Jackson MZ, Gruner KA, Qin C, Tourtellotte WG. A neuron autonomous role for the familial dysautonomia gene ELP1 in sympathetic and sensory target tissue innervation. Development. 2014. PMID: 25139957.
Bochner R, Ziv Y, Zeevi D, et al. Phosphatidylserine increases IKBKAP levels in a humanized knock-in IKBKAP mouse model. Hum Mol Genet. 2013. PMID: 23824189.

Sources

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	38
Resolved	38
Unresolved (possible confabulation)	0
Unverifiable	0
References weighed for topical relevance	38
On topic	7
Off topic	8

References that may not be about this subject

These identifiers resolve, so they are not fabrications, but the records they resolve to share almost none of this report's vocabulary. That is a clue and not a verdict - a paper can be relevant in ways its title and abstract do not spell out - so read them before deciding:

PMID:37000283 (1 mention) - An assessment of vegetation cover of Mysuru City, Karnataka State, India, using deep convolutional neural networks.
shared terms: model
PMID:32623925 (3 mentions) - Genetically Predicted Blood Pressure Across the Lifespan: Differential Effects of Mean and Pulse Pressure on Stroke Risk.
shared terms: disease
PMID:20857273 (3 mentions) - [Psychotherapy of Asperger syndrome in adults].
shared terms: none
PMID:24007805 (3 mentions) - The effect of color priming on infant brain and behavior.
shared terms: none
PMID:38168126 (1 mention) - A 3-year follow-up clinical study on the preservation for vitality of involved tooth in jaw cysts through an innovative method.
shared terms: none
PMID:21725277 (4 mentions) - Myocardial dysfunction in neonatal sepsis: a tissue Doppler imaging study.
shared terms: none
PMID:23824189 (1 mention) - A calcineurin-dependent switch controls the trafficking function of α-arrestin Aly1/Art6.
shared terms: cell, model
DOI:10.1161/HYPERTENSIONAHA.120.15267 (4 mentions) - Carbidopa for Afferent Baroreflex Failure in Familial Dysautonomia
shared terms: failure

Weighed against this report's own most characteristic terms: elp1, autonomic, loss, crise, disease, gene, elongator, retinal, aspiration, sensory, neuron, failure, progressive, palma, ataxia, cell, neuropathy, complex, model, ganglion.

All extracted references resolved successfully. Resolving is not the same as being relevant, though - see the references listed above as possibly off topic.

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Outcome	Count
Terms checked	74
Resolved	68
Unresolved (possible confabulation)	3
Obsolete	0
Unverifiable	3
Terms whose name was checked	57
Terms named correctly	21
Terms named as a different term	19
Terms whose name is worth a second look	17

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

HP:0100799 (1 mention) - the report calls it "smooth tongue"; HP calls it Neoplasm of the middle ear
HP:0001315 (2 mentions) - the report calls it "Depressed / absent deep tendon reflexes — ~100%", "Areflexia"; HP calls it Diminished deep tendon reflex**
HP:0002131 (2 mentions) - the report calls it "Ataxia (proprioceptive)"; HP calls it Episodic ataxia
HP:0000632 (2 mentions) - the report calls it "Optic neuropathy"; HP calls it Lacrimation abnormality
HP:0005112 (2 mentions) - the report calls it "abnormal autonomic nervous system physiology", "Autonomic crises"; HP calls it Abdominal aortic aneurysm
HP:0002326 (1 mention) - the report calls it "hypertension"; HP calls it Transient ischemic attack
HP:0011169 (1 mention) - the report calls it "Blood pressure lability / baroreflex failure — ~100%"; HP calls it Generalized clonic seizure**
HP:0002102 (1 mention) - the report calls it "Recurrent aspiration pneumonia — ~90%"; HP calls it Pleuritis**
HP:0000739 (1 mention) - the report calls it "Anxiety and emotional lability — very frequent"; HP calls it Anxiety**
HP:0011036 (1 mention) - the report calls it "Increased serum dopamine-to-norepinephrine ratio"; HP calls it Abnormality of renal excretion
CL:0011003 (2 mentions) - the report calls it "peripheral autonomic neuron"; CL calls it magnocellular neurosecretory cell
UBERON:0002393 (2 mentions) - the report calls it "Enteric nervous system", "enteric nervous system"; UBERON calls it pharyngotympanic tube
UBERON:0002205 (2 mentions) - the report calls it "Tongue fungiform papillae", "fungiform papilla"; UBERON calls it manubrium of sternum
UBERON:0001291 (1 mention) - the report calls it "lacrimal gland"; UBERON calls it thick ascending limb of loop of Henle
NCIT:C29435 (3 mentions) - the report calls it "Diazepam"; NCIT calls it DNA Minor Groove Binding Agent SG2000
NCIT:C505 (3 mentions) - the report calls it "Clonidine"; NCIT calls it Fluorouracil
NCIT:C471 (2 mentions) - the report calls it "Carbidopa"; NCIT calls it Enzyme Inhibitor
NCIT:C61708 (1 mention) - the report calls it "Dexmedetomidine"; NCIT calls it Dextroamphetamine Saccharate
NCIT:C874 (1 mention) - the report calls it "Fludrocortisone – avoid"; NCIT calls it Thiamine

Unresolved terms

These identifiers do not exist in an ontology that resolved other terms from the same prefix, so they were most likely invented:

HP:0000167 (2 mentions), reported as "atrophic fungiform papillae", "Absent fungiform papillae" - HP does not contain this term
ECTO:0001093 (1 mention), reported as "exposure to psychosocial stress" - ECTO does not contain this term
ECTO:0000000 (1 mention) - ECTO does not contain this term

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

HP:0007021 (2 mentions) - the report calls it "Nociceptor loss / pain insensitivity"; HP calls it Pain insensitivity
HP:0010829 (1 mention) - the report calls it "Decreased temperature sensation — ~90%"; HP calls it Impaired temperature sensation**
HP:0002020 (3 mentions) - the report calls it "Gastroesophageal reflux — ~85%", "Gastroesophageal reflux"; HP calls it Gastroesophageal reflux**
HP:0002098 (1 mention) - the report calls it "abnormal breathing regulation"; HP calls it Respiratory distress, and lists "Labored breathing" among its other names
HP:0002751 (2 mentions) - the report calls it "Kyphoscoliosis — ~90% by adolescence", "Kyphoscoliosis"; HP calls it Kyphoscoliosis**
GO:0033588 (4 mentions) - the report calls it "Elongator holoenzyme complex", "Cytoplasmic Elongator complex", "Elongator complex"; GO calls it elongator holoenzyme complex, and lists "Elongator core complex" among its other names
GO:0002098 (3 mentions) - the report calls it "tRNA wobble uridine modification", "tRNA wobble modification"; GO calls it tRNA wobble uridine modification
GO:0006915 (2 mentions) - the report calls it "Neuronal apoptosis during development", "apoptotic process"; GO calls it apoptotic process**, and lists "induction of apoptosis by p53" among its other names
GO:0090128 (1 mention) - the report calls it "regulation of synaptonemal complex assembly"; GO calls it regulation of synapse maturation
UBERON:0000044 (3 mentions) - the report calls it "Dorsal root ganglion", "dorsal root ganglion", "DRG"; UBERON calls it dorsal root ganglion, and lists "DRG" among its other names
UBERON:0002440 (3 mentions) - the report calls it "Sympathetic chain ganglia", "sympathetic ganglion", "Sympathetic ganglion"; UBERON calls it inferior cervical ganglion, and lists "stellate ganglion" among its other names
GO:0005874 (1 mention) - the report calls it "Microtubule cytoskeleton"; GO calls it microtubule
GO:0005739 (1 mention) - the report calls it "Mitochondria"; GO calls it mitochondrion, and lists "mitochondria" among its other names
UBERON:0001782 (1 mention) - the report calls it "retina"; UBERON calls it pigmented layer of retina, and lists "pigmented retina" among its other names
HP:0000007 (2 mentions) - the report calls it "Autosomal recessive", "Inheritance pattern: Autosomal recessive"; HP calls it Autosomal recessive inheritance
NCIT:C935 (1 mention) - the report calls it "Midodrine"; NCIT calls it Vindesine Sulfate, and lists "Gesidine" among its other names
HP:0002100 (1 mention) - the report calls it "Recurrent aspiration"; HP calls it Recurrent aspiration pneumonia

Terms named inconsistently

The report gives these identifiers more than one name of its own:

HP:0000167 - called "atrophic fungiform papillae", "Absent fungiform papillae"
HP:0001315 - called "Depressed / absent deep tendon reflexes** — ~100%", "Areflexia"
HP:0005112 - called "abnormal autonomic nervous system physiology", "Autonomic crises"
HP:0002020 - called "Gastroesophageal reflux** — ~85%", "Gastroesophageal reflux"
HP:0002751 - called "Kyphoscoliosis** — ~90% by adolescence", "Kyphoscoliosis"
GO:0033588 - called "Elongator holoenzyme complex", "Cytoplasmic Elongator complex", "Elongator complex"
GO:0002098 - called "tRNA wobble uridine modification", "tRNA wobble modification"
GO:0006915 - called "Neuronal apoptosis** during development", "apoptotic process"
CL:0000198 - called "nociceptor", "Nociceptor"
CL:0000740 - called "retinal ganglion cell", "Retinal ganglion cells", "Retinal ganglion cell"
UBERON:0000044 - called "Dorsal root ganglion", "dorsal root ganglion", "DRG"
UBERON:0002440 - called "Sympathetic chain ganglia", "sympathetic ganglion", "Sympathetic ganglion"
UBERON:0002393 - called "Enteric nervous system", "enteric nervous system"
UBERON:0001675 - called "Trigeminal ganglion", "trigeminal ganglion"
UBERON:0002205 - called "Tongue fungiform papillae", "fungiform papilla"
HP:0000007 - called "Autosomal recessive", "Inheritance pattern: Autosomal recessive"

Prefixes with no resolver

Terms carrying these prefixes were not checked either way, because no configured ontology covers them. An unrecognised prefix may name an ontology this run could not reach as easily as one that does not exist, so nothing here is evidence of fabrication: ORPHA, MGI.

Ask OpenScientist

OpenScientist Report

Inheritance

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

External Assertions

Medical Actions

Environmental Factors

Diagnosis

Progression

Prevalence

Differential Diagnoses

Clinical Trials

Animal Models

Source YAML

References & Deep Research

References

Deep Research

1. Disease Information

2. Etiology

2.1 Disease Causal Factors

2.2 Risk Factors

2.3 Protective Factors

2.4 Gene–Environment Interactions

3. Phenotypes

3.1 Neurological / Sensory

3.2 Autonomic / Cardiovascular

3.3 Gastrointestinal

3.4 Respiratory

3.5 Musculoskeletal

3.6 Genitourinary

3.7 Behavioral / Cognitive

3.8 Laboratory

3.9 Onset, Progression, Severity, QOL

4. Genetic / Molecular Information

4.1 Causal Gene

4.2 Pathogenic Variants

4.3 Modifier Genes

4.4 Epigenetic Information

4.5 Chromosomal Abnormalities

5. Environmental Information

6. Mechanism / Pathophysiology

6.1 Ordered Causal Chain

6.2 Molecular Pathways Involved

6.3 Cellular Processes

6.4 Protein Dysfunction

6.5 Metabolic / Biochemical Changes

6.6 Tissue Damage Mechanisms

6.7 Molecular Profiling

7. Anatomical Structures Affected

7.1 Organ Level

7.2 Tissue and Cell Level

7.3 Subcellular Level

7.4 Localization

8. Temporal Development

8.1 Onset

8.2 Progression / Stages

8.3 Patterns

9. Inheritance and Population

9.1 Epidemiology

9.2 Genetic Etiology Details

9.3 Population Demographics

10. Diagnostics

10.1 Clinical Diagnostic Criteria (Historical Cardinal Five)

10.2 Confirmatory Testing

10.3 Imaging / Functional Tests

10.4 Screening

10.5 Differential Diagnosis

11. Outcome / Prognosis

11.1 Survival and Mortality

11.2 Morbidity and Function

11.3 Complications

11.4 Prognostic Factors

12. Treatment

12.1 Pharmacotherapy (Symptomatic)

12.2 Disease-Modifying / Advanced Therapies (Investigational)

12.3 Surgical/Interventional