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Classifications

Harrison's Part

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Inheritance

2

Autosomal dominant, 22q11.2 deletion HP:0000006

The 22q11.2 deletion is usually de novo but is transmitted as an autosomal dominant trait once present, so an affected individual has a fifty percent transmission risk. This is the mode that applies to the largest identified genetic subgroup, and it is why deletion testing changes reproductive counselling for the patient as well as for the parents.

Autosomal dominant inheritance

Show evidence (1 reference)

PMID:32049433 SUPPORT Human Clinical

"Early identification of a 22q11.2 deletion in the neonate or infant when other syndromic features may not be apparent allows for timely parental screening for reproductive counseling and anticipatory evaluation of cardiac and noncardiac features."

States the reproductive-counselling consequence that follows from the dominant transmission of the deletion.

Autosomal recessive, biallelic TMEM260 or NKX2-6 HP:0000007

Biallelic loss-of-function variants in TMEM260 and biallelic homeodomain-disrupting variants in NKX2-6 both cause this malformation recessively. The counselling implication is opposite to the deletion case: a one in four sibling recurrence risk with carrier parents, rather than a low recurrence risk with a fifty percent transmission risk. Both were found in consanguineous or founder settings, which is where recessive causes surface first.

Autosomal recessive inheritance

Show evidence (2 references)

PMID:38351237 SUPPORT Human Clinical

"the biallelic loss-of-function variants of which have recently been associated with structural heart defects and renal anomalies syndrome (SHDRA)"

Establishes biallelic, and therefore recessive, inheritance for the TMEM260 route.

PMID:32198970 SUPPORT Human Clinical

"Two consanguineous families with TA were previously identified to have homozygous nonsense variants within the gene NKX2-6."

Establishes homozygous, and therefore recessive, inheritance for the NKX2-6 route, in the consanguineous setting where it was found.

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Discussions and Knowledge Gaps

4

Why do infants with truncus arteriosus and a 22q11.2 deletion appear to have an inverse risk of in-hospital death despite carrying more comorbidity?

CONTROVERSY OPEN deletion_positive_survival_paradox

Attached to

pathophysiology#Cardiac neural crest and second heart field program disruption pathophysiology#Perioperative myocardial ischaemia

The national inpatient analysis found 22q11.2 deletion associated with an inverse risk of death despite more non-cardiac comorbidity, and a separate review reports that deletion patients have more perioperative complications without higher surgical mortality. Taken at face value the finding is paradoxical. Several explanations compete and imply different things. Deletion-positive infants are identified earlier and enter tertiary care sooner, so the association may be a surrogate for timely referral rather than a biological protection. Their anatomy may differ systematically, and there is a hint of this in an older series where deletion-positive patients were enriched for types with pulmonary stenosis, which would restrict pulmonary flow and postpone decompensation. Or the finding may be an artefact of administrative coding, since a deletion diagnosis has to be recorded to be counted and is more likely to be recorded in survivors who reach genetic testing. The last of these would make the result an artefact of exactly the data source that produced it.

Proposed experiments

Prospective registry comparison of outcomes by 22q11.2 status with anatomic and referral covariates

exp_pta_deletion_status_outcome_registry

In a multicentre congenital cardiac surgical registry with universal deletion testing at diagnosis, compare operative and one-year mortality by deletion status, adjusting for Van Praagh anatomic subtype, presence of pulmonary or truncal valve stenosis, coronary anomaly, age at referral, and preoperative clinical state.

Decision criterion

A persisting survival advantage after adjustment for anatomy and referral timing would point to a genuine biological or care-pathway effect worth explaining; loss of the association on adjustment would establish it as confounding and would retire the paradox.

Show evidence (2 references)

PMID:32557823 SUPPORT Human Clinical

"22q11.2 deletion syndrome was associated with an inverse risk of death despite having more noncardiac comorbidities"

The observation that creates the controversy.

PMID:9316541 SUPPORT Human Clinical

"In truncus arteriosus communis, the rare type A3 with major aortopulmonary collateral arteries and pulmonary ostial stenosis and type A1 with pulmonary artery stenosis are associated with del 22q11."

Supports the anatomic-difference explanation, since the deletion-associated subtypes carry pulmonary flow restriction; PARTIAL because the series of 15 patients is small and outcomes are not reported.

Why does a targeted Nkx2.6 mutation leave mice normal when a homozygous NKX2.6 homeodomain variant causes common arterial trunk in humans?

HUMAN MODEL MISMATCH OPEN nkx2_6_mouse_human_discrepancy

Attached to

pathophysiology#Cardiac neural crest and second heart field program disruption pathophysiology#Failure of aorticopulmonary septation

The human evidence is strong: autozygosity mapping in a large consanguineous family localised the lesion to 8p21, the variant sits in the homeodomain, and the corresponding substitution in the NKX2.5 surrogate substantially reduced transcriptional activation, DNA binding, and synergy at target promoters. Yet Nkx2.6 null mice are normal, and the reason appears to be that Nkx2.5 expression expands into the territory Nkx2.6 vacates. If that complementation is mouse-specific, then the mouse null is simply the wrong assay for this gene and its normality carries no evidential weight against the human finding. If instead complementation also operates in humans, then a simple loss-of-function model cannot be right and the F151L variant is doing something a null does not, most plausibly acting as a dominant negative on shared NKX partners. The two readings imply different variant interpretation rules for this gene in a clinical laboratory, which is why this is not merely a modelling curiosity. The human side of the discrepancy has since strengthened: further individuals with biallelic homeodomain-disrupting NKX2-6 variants have been reported, so the association no longer rests on the single original kindred while the mouse null remains normal.

Proposed experiments

Comparison of an Nkx2.6 F151L knock-in against an Nkx2.6 null on matched backgrounds

exp_nkx26_knockin_versus_null

Generate a knock-in mouse carrying the orthologous homeodomain substitution alongside a true null on the same background, assess outflow tract septation in both, and map Nkx2.5 expression domains in each to determine whether the compensatory expansion occurs in the knock-in as it does in the null.

Decision criterion

A septation defect in the knock-in but not the null would establish a dominant-negative rather than loss-of-function mechanism and would mean null alleles should not be equated with this missense variant; normality of both, with equivalent Nkx2.5 expansion, would confirm that mouse complementation makes the model uninformative for this human gene.

Show evidence (3 references)

PMID:15649947 SUPPORT Model Organism

"mice homozygous for a targeted mutation of Nkx2.6 are normal. However, in these mice, it has been shown that Nkx2.5 expression expands into regions lacking Nkx2.6, suggesting functional complementation."

States the mismatch and the compensation hypothesis proposed to explain it, in the same paper that reports the human variant.

PMID:32198970 SUPPORT Human Clinical

"Two consanguineous families with TA were previously identified to have homozygous nonsense variants within the gene NKX2-6."

Independent replication of the human association, which is what makes the normal mouse null a genuine discrepancy rather than a reason to doubt the original report.

PMID:32198970 SUPPORT Human Clinical

"NKX2-6 is a known downstream target of TBX1, an important transcriptional regulator implicated in the cardiac phenotype of 22q11.2 microdeletion syndrome."

Places NKX2-6 downstream of TBX1, which unifies the recessive NKX2-6 route and the dominant 22q11.2 route into one pathway and is why both are curated against the same trigger node.

Is the genetic architecture of deletion-negative truncus arteriosus population-specific, and what does that mean for genetic testing offered outside the populations it was described in?

OPEN QUESTION OPEN population_specific_genetic_architecture

Attached to

pathophysiology#Cardiac neural crest and second heart field program disruption

TMEM260 emerged as a major cause of deletion-negative truncus arteriosus in Japan, but the signal rests on a founder variant carried at 0.36 percent allele frequency in that population and estimated to be about 23 000 years old. A founder allele's contribution is by construction a property of the population, not of the gene, so the projection that about a quarter of Japanese cases are homozygous for it says nothing about how often TMEM260 explains cases elsewhere. Two practical consequences follow and neither is settled. A targeted panel built on the Japanese finding may have low yield in other populations, while a broad sequencing approach would find whatever the local architecture is. And the absence of comparable studies elsewhere means the field currently cannot distinguish "TMEM260 is a Japanese founder effect" from "TMEM260 is a general cause that was first found in Japan."

Proposed experiments

Multi-ancestry whole-genome sequencing of deletion-negative truncus arteriosus

exp_pta_multiancestry_sequencing

Sequence deletion-negative truncus arteriosus cohorts recruited across several ancestries, report diagnostic yield by gene and by ancestry, and test specifically whether biallelic TMEM260 loss of function contributes outside East Asian populations and at what frequency.

Decision criterion

A comparable TMEM260 contribution across ancestries would establish it as a general cause and justify including it on universal panels; a contribution confined to populations carrying the founder allele would establish the architecture as population-specific and would argue for genome-wide sequencing rather than transplanted panels.

Show evidence (2 references)

PMID:38351237 SUPPORT Human Clinical

"This study highlights TMEM260, especially c.1617del, as a major genetic cause of TA in the Japanese population."

The authors localise their own claim to the Japanese population, which is the premise of this question.

PMID:38351237 SUPPORT Human Clinical

"However, no major causes of TA other than 22q11.2 deletion have been reported."

States the prior state of knowledge that a single-population study has now changed, and by implication how thin the comparative evidence is.

What accounts for the majority of truncus arteriosus cases that carry neither a 22q11.2 deletion nor an identified monogenic cause?

KNOWLEDGE GAP OPEN majority_of_cases_genetically_unexplained

Attached to

pathophysiology#Cardiac neural crest and second heart field program disruption pathophysiology#Failure of aorticopulmonary septation

The deletion explains 12 to 35 percent of cases. Sequencing in deletion-negative patients has now identified TMEM260, GATA6, and NOTCH1 variants, but in a single small population-specific cohort. Across the whole disease, most cases still have no molecular diagnosis. Three candidate explanations are open. There may be further monogenic causes that adequately powered multi-ancestry sequencing will find, which the recent TMEM260 result makes plausible. Causation may be substantially oligogenic or multifactorial, with the developmental program failing on a combination of variants none of which is individually diagnostic. Or non-genetic causes may account for a real share, with maternal pregestational diabetes and retinoic-acid-pathway exposures the leading candidates and plausibly interacting with genotype. These are not exclusive, and distinguishing their relative contributions determines whether the right investment is deeper sequencing or exposure epidemiology.

Proposed experiments

Trio sequencing of unexplained truncus arteriosus with linked maternal exposure data

exp_pta_trio_sequencing_with_exposure_data

Sequence parent-child trios for cases negative for 22q11.2 deletion and known monogenic causes, quantify the de novo variant burden in outflow-tract developmental genes against matched controls, and link each case to prospectively recorded maternal pregestational diabetes status and periconceptional retinoid exposure.

Decision criterion

Significant de novo burden in outflow-tract developmental pathways would support further monogenic causes and justify deeper sequencing; a null burden with strong exposure association would redirect effort to exposure epidemiology and prevention.

Show evidence (2 references)

PMID:38351237 SUPPORT Human Clinical

"The most common cause of TA is 22q11.2 deletion syndrome, accounting for 12-35% of all TA cases. However, no major causes of TA other than 22q11.2 deletion have been reported."

Quantifies the explained fraction and states that the remainder was unaccounted for before this study.

PMID:38884753 SUPPORT Human Clinical

"Other congenital malformation syndromes and variants in genes encoding TBX, GATA, and NKX transcription factors and some signaling proteins have also been reported as its etiology."

Documents the scattered additional genetic causes reported to date; PARTIAL because it does not quantify what share of cases they explain.

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Pathophysiology

11

Cardiac neural crest and second heart field program disruption

The outflow tract is built by two cell populations acting together: cardiac neural crest cells migrating through pharyngeal arches three, four, and six to form the elastogenic smooth muscle of the aorticopulmonary septum, and second heart field mesoderm adding myocardium to the elongating outflow tract. Their crosstalk is patterned by TBX, GATA, and NKX transcription factors and by FGF, BMP, and Wnt signalling. Disruption anywhere in this unit, whether by 22q11.2 deletion, a monogenic variant, or a teratogen, converges on the same failure.

Cardiac neural crest cell CL:0011012

cardiac neural crest cell development involved in outflow tract morphogenesis GO:0061309 ↓ DECREASED neural crest cell migration GO:0001755 ↓ DECREASED

Outflow tract UBERON:0004145

Experimental models

Splotch mutant mouse OTHER Splotch disrupts neural-crest-derived cell populations, which is the trigger node here.

Tbx1 conditional null mouse with beta-catenin dosage rescue OTHER Tbx1 inactivation in anterior heart field mesoderm models the second heart field arm of the trigger node, complementing the neural crest arm modelled by Splotch.

Downstream

Failure of aorticopulmonary septation Without a properly specified and positioned neural-crest-derived septal population, the conotruncal ridges do not fuse and no aorticopulmonary septum forms.

Show evidence (1 reference)

PMID:38884753 SUPPORT Human Clinical

"Other congenital malformation syndromes and variants in genes encoding TBX, GATA, and NKX transcription factors and some signaling proteins have also been reported as its etiology."

Identifies the transcription-factor families whose disruption produces the malformation, which is what makes this a developmental-program defect rather than a single-gene disease.

Failure of aorticopulmonary septation

The defining embryologic event, occurring in weeks five to eight of human gestation. The conotruncal ridges fail to fuse and spiral, so no aorticopulmonary septum divides the common trunk into aorta and pulmonary trunk. The same septal deficiency accounts for the ventricular septal defect, because the conal septum that would have closed the outflow portion of the interventricular septum is absent or malformed. That is why the ventricular septal defect here is not an independent second lesion but part of the same failure.

outflow tract septum morphogenesis GO:0003148 ⇓ LOSS OF FUNCTION

Truncus arteriosus UBERON:0002061 Outflow tract septum UBERON:0004142

Experimental models

Splotch mutant mouse OTHER The mutant reproduces the septation failure itself.

Tbx1 conditional null mouse with beta-catenin dosage rescue OTHER The mutant reproduces the failure of septation between aorta and pulmonary trunk.

Downstream

Single arterial trunk overriding a ventricular septal defect The unseptated trunk persists as a single vessel with one semilunar valve, sitting over the unclosed outflow portion of the interventricular septum.

Show evidence (1 reference)

PMID:38884754 SUPPORT Human Clinical

"When the process of outflow tract septation fails, a single common outflow vessel persists resulting in a serious clinical condition known as persistent truncus arteriosus or common arterial trunk."

States the septation-failure-to-single-vessel step as the definition of the disease.

Single arterial trunk overriding a ventricular septal defect

The anatomic result. One vessel leaves the heart through a single semilunar valve and gives rise to the coronary arteries, the pulmonary arteries, and the systemic circulation. Because both ventricles eject into it across a large non-restrictive ventricular septal defect, systemic and pulmonary venous return mix obligatorily at the trunk, and both ventricles see systemic pressure.

Interventricular septum UBERON:0002094

Downstream

Obligatory mixing of systemic and pulmonary venous return A single outlet for both ventricles forces complete admixture of oxygenated and deoxygenated blood.

Unobstructed pulmonary blood flow at systemic pressure Pulmonary arteries arising directly from the trunk are exposed to systemic pressure with no interposed obstruction.

Truncal valve dysfunction The single semilunar valve is frequently dysplastic, with an abnormal cusp number, and is prone to regurgitation and, less often, stenosis.

Coronary ostial anomaly Coronary arteries arise from an abnormal single-trunk root rather than from a normally septated aortic sinus template, so their origins are frequently anomalous.

Show evidence (1 reference)

PMID:38351237 SUPPORT Human Clinical

"Truncus Arteriosus (TA) is a congenital heart disease characterized by a single common blood vessel emerging from the right and left ventricles instead of the main pulmonary artery and aorta."

The definitional statement of this node, naming the single vessel and the fact that it receives ejection from both ventricles.

Obligatory mixing of systemic and pulmonary venous return

Because there is one outlet, mixing is complete and is not modulated by shunt size or direction. Arterial saturation is therefore set by the proportion of pulmonary to systemic flow rather than by any restrictive orifice, which has a counterintuitive consequence: the more the lungs are flooded, the pinker the baby looks, so improving colour in an untreated infant is a sign of worsening physiology rather than improvement.

Downstream

Cyanosis Admixture of desaturated systemic venous return lowers arterial oxygen saturation.

Show evidence (1 reference)

PMID:38351237 SUPPORT Human Clinical

"a single common blood vessel emerging from the right and left ventricles"

The single common outlet from both ventricles is the anatomic basis of obligatory mixing.

Unobstructed pulmonary blood flow at systemic pressure

In most anatomic subtypes nothing restricts flow into the pulmonary arteries. The pulmonary bed therefore sees systemic pressure directly, and pulmonary blood flow is governed purely by the ratio of pulmonary to systemic vascular resistance. In the first hours of life high neonatal pulmonary resistance masks the problem; over the following days that resistance falls physiologically, flow rises steeply, and the infant decompensates. The clinical corollary is that a well-looking newborn with this lesion is not reassuring, merely early.

Pulmonary artery UBERON:0002012

Downstream

Pulmonary overcirculation and volume-overload heart failure As pulmonary vascular resistance falls after birth, pulmonary blood flow rises and volume-loads the ventricles.

Pulmonary vascular obstructive disease Sustained high-flow, high-pressure exposure of the pulmonary bed drives progressive remodelling toward fixed resistance.

Show evidence (1 reference)

PMID:38884754 SUPPORT Human Clinical

"the outflow tract of the heart is divided into two distinct channels to separate the oxygenated systemic blood flow from the deoxygenated pulmonary circulation"

States the function of normal septation, whose absence leaves the pulmonary circulation exposed to systemic pressure.

Truncal valve dysfunction

The single semilunar valve is frequently abnormal, with two, three, four, or rarely five cusps, and is often dysplastic. Regurgitation adds volume load on top of the pulmonary overcirculation. Stenosis is less common but worse tolerated, because both ventricles eject through this one valve, so a single stenotic orifice imposes pressure load on the whole heart at once. Truncal valve disease is a principal determinant of both operative difficulty and long-term reoperation.

Downstream

Pulmonary overcirculation and volume-overload heart failure Truncal regurgitation adds regurgitant volume to the already high pulmonary flow, compounding ventricular volume overload.

Show evidence (1 reference)

PMID:837493 SUPPORT Human Clinical

"Bicuspid truncal valve was observed in six cases (20%) and tricuspid in 21 cases (70%)."

Autopsy series of 30 hearts quantifying truncal valve cusp number, which is the morphological abnormality this node asserts.

Coronary ostial anomaly

Coronary origins are abnormal in a large fraction of cases, because the coronary buds address a single unseptated root rather than the normal paired aortic sinuses. There is no single consistent pattern, which is precisely the problem: the surgeon must map the coronaries individually before repair, and an unrecognised anomalous course is an independent driver of perioperative mortality.

Downstream

Perioperative myocardial ischaemia An anomalous coronary origin or course can be compressed, distorted, or divided during conduit placement and root reconstruction.

Show evidence (2 references)

PMID:837493 SUPPORT Human Clinical

"There was a strong tendency for the left coronary artery to arise from a more posterior level than it does normally from the aorta."

Documents the systematic displacement of the coronary origin from its normal aortic position, which is the consequence of the trunk not having septated into a normal aortic root.

PMID:837493 SUPPORT Human Clinical

"Single coronary artery was observed in four cases (three with tricuspid and one with quadricuspid truncal valves)."

Quantifies the most surgically consequential variant, a single coronary artery, in four of 30 hearts.

Pulmonary overcirculation and volume-overload heart failure

The clinical presentation in the first weeks: tachypnoea, poor feeding, sweating, failure to thrive, and hepatomegaly, in an infant who is only mildly desaturated. It is high-output failure from excessive pulmonary blood flow, not pump failure, which is why the treatment before surgery is to limit pulmonary flow rather than to augment contractility.

Downstream

Pulmonary vascular obstructive disease Continuing high-flow high-pressure exposure remodels the pulmonary arterioles.

Pulmonary vascular obstructive disease

The end of the untreated natural history, and the reason this is a neonatal surgical disease rather than an elective one. Sustained exposure of the pulmonary bed to systemic pressure and high flow produces fixed obstructive remodelling within the first year or two of life. Once resistance is fixed, closing the ventricular septal defect is contraindicated for the same reason it is in Eisenmenger physiology, and the operation that would have been curative at two weeks becomes lethal.

Pulmonary artery UBERON:0002012

Perioperative myocardial ischaemia

Ischaemic injury around the time of repair, from anomalous coronary anatomy, from coronary distortion during root reconstruction, or from the mismatch between a volume-loaded ventricle and a diastolic pressure lowered by truncal regurgitation. It is one of the mechanisms behind an in-hospital mortality that remains around one in ten even in the contemporary era.

Show evidence (1 reference)

PMID:32557823 SUPPORT Human Clinical

"Overall, 3009 neonates met inclusion criteria; a total of 326 patients died during the hospitalization (10.8%)."

Quantifies contemporary in-hospital mortality in a national cohort; PARTIAL because ischaemia is not separately attributed.

Cyanosis

Present from birth but characteristically mild, because pulmonary blood flow is high. This is why the lesion is easy to miss on inspection and why newborn pulse-oximetry screening matters more here than a visual assessment does.

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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

12

Cardiovascular 5

Truncus arteriosus OBLIGATE HP:0001660

Show evidence (1 reference)

PMID:38351237 SUPPORT Human Clinical

"Truncus Arteriosus (TA) is a congenital heart disease characterized by a single common blood vessel emerging from the right and left ventricles instead of the main pulmonary artery and aorta."

The obligate defining anatomy.

Ventricular septal defect OBLIGATE HP:0001629

Show evidence (1 reference)

PMID:38351237 SUPPORT Human Clinical

"a single common blood vessel emerging from the right and left ventricles"

The trunk receiving ejection from both ventricles entails the septal defect that lets it do so.

Congestive heart failure VERY_FREQUENT HP:0001635

Temporal: ACUTE

Aortic regurgitation FREQUENT HP:0001659

Show evidence (1 reference)

PMID:837493 SUPPORT Human Clinical

"Bicuspid truncal valve was observed in six cases (20%) and tricuspid in 21 cases (70%)."

Establishes the abnormal cusp anatomy that predisposes to regurgitation; PARTIAL because the series reports valve morphology at autopsy and not the presence or severity of regurgitation in life.

Pulmonary arterial hypertension FREQUENT HP:0002092

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:38884754 SUPPORT Human Clinical

"the outflow tract of the heart is divided into two distinct channels to separate the oxygenated systemic blood flow from the deoxygenated pulmonary circulation"

States the separation that normally protects the pulmonary circulation from systemic pressure, whose absence produces pulmonary hypertension; PARTIAL because the complication is not described in the source.

Integument 1

Cyanosis VERY_FREQUENT HP:0000961

Temporal: CHRONIC

Metabolism 1

Hypocalcemia OCCASIONAL HP:0002901

Show evidence (1 reference)

PMID:32049433 SUPPORT Human Clinical

"the most common features include: facial dysmorphia, hypocalcemia, palate and speech disorders, feeding and gastrointestinal disorders, immunodeficiency, recurrent infections, neurodevelopmental and psychiatric disorders, and congenital heart disease"

Lists hypocalcaemia among the core features of the syndrome present in a substantial minority of these infants.

Respiratory 1

Tachypnea FREQUENT HP:0002789

Growth 1

Failure to thrive FREQUENT HP:0001508

Course: PROGRESSIVE

Other 3

Abnormal coronary artery origin FREQUENT HP:0011636

Show evidence (2 references)

PMID:837493 SUPPORT Human Clinical

"Specimens of heart from 30 subjects with persistent truncus arteriosus were studied for the nature and sites of coronary arterial origin."

The autopsy series that characterised coronary origin in this malformation.

PMID:837493 SUPPORT Human Clinical

"It was common for the posterior descending artery to arise from the left circumflex artery. This arrangement was noted in eight of 25 cases (32%)"

A specific anomalous arrangement in 32 percent of cases, supporting the FREQUENT band with a counted denominator rather than a review estimate.

Right aortic arch HP:0012020

Show evidence (1 reference)

PMID:38351237 SUPPORT Human Clinical

"right aortic arch (RAA) in Patient 2"

Documents a right aortic arch in a patient in this truncus arteriosus case series, which establishes the association without supporting any particular rate.

Interrupted aortic arch OCCASIONAL HP:0011611

Show evidence (1 reference)

PMID:32049433 SUPPORT Human Clinical

"a subset of conotruncal defects (tetralogy of Fallot, truncus arteriosus, interrupted aortic arch type B), conoventricular and/or atrial septal defects, and aortic arch anomalies"

Places truncus arteriosus and interrupted aortic arch together within the same 22q11.2 conotruncal spectrum.

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Genetic Associations

5

TBX1

Gene: TBX1 hgnc:11592 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (2 references)

PMID:38351237 SUPPORT Human Clinical

"The most common cause of TA is 22q11.2 deletion syndrome, accounting for 12-35% of all TA cases."

Quantifies the deletion's contribution, which is the basis for treating this locus as the leading cause.

PMID:38884753 SUPPORT Human Clinical

"Integrated human genetics and molecular/developmental biology studies have revealed that truncus arteriosus is highly associated with 22q11.2 deletion syndrome."

Independent statement of the association from a genetics review.

TMEM260

Gene: TMEM260 hgnc:20185 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (2 references)

PMID:38351237 SUPPORT Human Clinical

"Among five patients, we identified pathogenic variants in TMEM260; the biallelic loss-of-function variants of which have recently been associated with structural heart defects and renal anomalies syndrome (SHDRA)."

Establishes biallelic TMEM260 loss of function as a cause in five of 11 deletion-negative patients.

PMID:38351237 SUPPORT Human Clinical

"Based on the allele frequency of the c.1617del variant in the Japanese population (0.36%), approximately 26% of Japanese patients afflicted with TA could harbor homozygous c.1617del variants."

Quantifies the founder variant's projected population-level contribution, and by construction its population specificity.

NKX2-6

Gene: NKX2-6 hgnc:32940 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (2 references)

PMID:15649947 SUPPORT Human Clinical

"We have used autozygosity mapping of a large consanguineous family segregating CAT to map the causative locus to chromosome 8p21. An F151L mutation was identified in the homeodomain of NKX2.6"

The mapping and variant identification in a segregating consanguineous family.

PMID:15649947 SUPPORT In Vitro

"Introduction of F157L into human NKX2.5 substantially reduced its transcription activating function, its synergism with partners at the atrial natriuretic factor (ANF) and connexin-40 (Cx40) promoters and its specific DNA binding."

Functional evidence for the variant's effect, obtained in the NKX2.5 surrogate because NKX2.6 targets were unknown.

GATA6

Gene: GATA6 hgnc:4174 relationship_type: CAUSATIVE variant_origin: DE_NOVO

Show evidence (1 reference)

PMID:38351237 SUPPORT Human Clinical

"In one patient, we identified a de novo pathogenic variant in GATA6"

The single-patient de novo finding, curated at the strength the source supports.

NOTCH1

Gene: NOTCH1 hgnc:7881 relationship_type: UNKNOWN variant_origin: DE_NOVO

Show evidence (1 reference)

PMID:38351237 SUPPORT Human Clinical

"in another patient, we identified a de novo probably pathogenic variant in NOTCH1"

The authors' own hedged classification, which is the reason this gene is not curated as causative.

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Medical Actions

4

Neonatal complete surgical repair

Action: cardiac surgery Ontology label: Cardiac Surgery NCIT:C157806

The definitive treatment and the only one that changes the outcome. The ventricular septal defect is closed so the trunk becomes the aorta and arises from the left ventricle alone, the pulmonary arteries are separated from the trunk, and continuity from the right ventricle to the pulmonary arteries is re-established with a conduit. It is performed in the neonatal period, before pulmonary vascular disease develops, and it carries an in-hospital mortality around one in ten in contemporary national data.

Mechanism Target:

INHIBITS Unobstructed pulmonary blood flow at systemic pressure — Separating the pulmonary arteries from the trunk and interposing a conduit removes the pulmonary bed's exposure to systemic pressure and unrestricted flow.

Show evidence (1 reference)

PMID:32557823 SUPPORT Human Clinical

"Overall, 3009 neonates met inclusion criteria; a total of 326 patients died during the hospitalization (10.8%)."

Establishes neonatal repair as standard practice at national scale and quantifies its mortality.

INHIBITS Obligatory mixing of systemic and pulmonary venous return — Closing the ventricular septal defect commits the trunk to the left ventricle and abolishes the obligatory admixture.

Show evidence (1 reference)

PMID:38884754 SUPPORT Human Clinical

"the outflow tract of the heart is divided into two distinct channels to separate the oxygenated systemic blood flow from the deoxygenated pulmonary circulation"

States the separation of circulations that the operation restores surgically; PARTIAL because the source describes normal development rather than the operation.

Show evidence (1 reference)

PMID:32557823 SUPPORT Human Clinical

"necrotizing enterocolitis (aOR = 3.10; 95% CI: 1.24-7.74; P = .015) and presence of venous thrombosis (aOR = 13.5; 95% CI: 6.7-27.2; P < .001)"

Identifies comorbidities carrying the highest adjusted operative risk, which is what perioperative planning acts on.

Serial right ventricle to pulmonary artery conduit replacement

Action: cardiac surgery Ontology label: Cardiac Surgery NCIT:C157806

A consequence of the repair rather than a treatment of the disease. The conduit does not grow, so it is outgrown and becomes obstructive, and it is replaced repeatedly through childhood and adolescence. This converts a neonatal emergency into a lifelong surgical relationship, and it is the main reason these patients need permanent congenital cardiology follow-up rather than discharge after successful repair.

Mechanism Target:

INHIBITS Pulmonary vascular obstructive disease — Maintaining an unobstructed conduit preserves the low-pressure separation of the pulmonary circulation that the original repair created.

Preoperative anticongestive medical therapy

Action: Pharmacotherapy NCIT:C15986

Agent: diuretic NCIT:C448

Diuresis and afterload reduction to control pulmonary overcirculation while the infant is prepared for surgery. It is a holding measure with a specific trap: supplemental oxygen lowers pulmonary vascular resistance and therefore increases pulmonary flow, so generous oxygen makes the physiology worse in an infant whose saturation looks reassuringly high.

Mechanism Target:

MODULATES Pulmonary overcirculation and volume-overload heart failure — Diuresis and afterload reduction relieve congestion without altering the anatomy that causes it.

Extracorporeal membrane oxygenation

Action: extracorporeal membrane oxygenation Ontology label: Extracorporeal Membrane Oxygenation NCIT:C171507

Rescue support, used in about seven percent of these admissions. Its association with a very high mortality odds ratio should be read as severity marking rather than harm: it is used in infants who are dying, and the confounding by indication is total.

Mechanism Target:

BYPASSES Perioperative myocardial ischaemia — Extracorporeal support maintains systemic perfusion and oxygenation while the injured myocardium recovers.

Show evidence (1 reference)

PMID:32557823 SUPPORT Human Clinical

"Extracorporeal membrane oxygenation utilization was 7.1%."

Quantifies how often extracorporeal support is used in this population.

Show evidence (1 reference)

PMID:32557823 SUPPORT Human Clinical

"Patients who received extracorporeal membrane oxygenation support or had cardiac catheterization procedure during the hospitalization had increased odds of mortality"

Reports the mortality association; PARTIAL and directionally uninterpretable as a treatment effect, because the sickest infants are the ones cannulated.

🌍

Environmental Factors

1

Maternal pregestational diabetes

No ECTO term is bound. Maternal pregestational diabetes is a maternal disease state rather than an exposure to an agent, and the ECTO exposure hierarchy has no term that expresses it without asserting a specific chemical exposure the sources do not support. A retinoic-acid mechanism is often proposed for diabetic embryopathy, namely hyperglycaemia-induced disturbance of embryonic retinoic acid catabolism sensitising the conotruncal field. It was in an earlier draft of this description and has been removed. The deep-research report sources it only to PMC identifiers that were never fetched or verified, and the one study cited here states outright that the teratogenic mechanism is unknown. Recording it as a lead in notes is honest; asserting it in a description backed by a source that disclaims it is not.

The best-established non-genetic risk factor, and the only modifiable one. The National Birth Defects Prevention Study puts the adjusted odds ratio for this malformation at 14.9 (95% CI 7.6 to 29.3), one of a handful of defects in that study exceeding a ten-fold increased risk. Unlike the genetic causes, this one is preventable in principle, which is why it carries prevention weight out of proportion to the fraction of cases it explains. No mechanism is asserted here: the source states the teratogenic mechanism is unknown.

Show evidence (2 references)

PMID:31454511 SUPPORT Human Clinical

"truncus arteriosus (adjusted odds ratio, 14.9; 95% confidence interval, 7.6-29.3)"

The disease-specific adjusted effect estimate from the National Birth Defects Prevention Study, and the strongest available evidence for this exposure. A roughly fifteen-fold adjusted odds ratio with a confidence interval well clear of one places this malformation among the defects most strongly associated with pregestational diabetes.

PMID:31454511 SUPPORT Human Clinical

"For some defect categories, and particularly for pregestational diabetes, there were few exposed cases, leading to imprecise estimates."

The authors' own precision caveat, which is why the confidence interval on the truncus arteriosus estimate is as wide as it is; PARTIAL because it qualifies the estimate rather than supporting the association.

Mechanism Target:

PREDISPOSES Cardiac neural crest and second heart field program disruption — Maternal hyperglycaemia during the fifth to eighth week of gestation is proposed to perturb the neural crest and second heart field program during outflow tract septation.

Show evidence (1 reference)

PMID:31454511 SUPPORT Human Clinical

"the teratogenic mechanism behind the increase risk for birth defects is still unknown"

PARTIAL, and deliberately so. This edge asserts that the exposure acts on the neural crest and second heart field program, and the source states plainly that the teratogenic mechanism is unknown. The association is strong and disease-specific; the step from association to this particular developmental mechanism is not evidenced, and the snippet records that rather than papering over it.

🔬

Diagnosis

4

Transthoracic echocardiography

The diagnostic test. It demonstrates the single trunk overriding the ventricular septal defect, the number and competence of the truncal valve cusps, the origin pattern of the pulmonary arteries that determines the anatomic subtype, and any arch anomaly. It is also the test that must be complete before surgery, because the operative plan depends on these details.

echocardiography NCIT:C16525

22q11.2 deletion testing

Should be performed in every infant with this diagnosis, not only in those who look syndromic. Guidelines specifically name truncus arteriosus as an indication, and the reason is practical: the deletion changes perioperative management through hypocalcaemia and immunodeficiency, changes recurrence counselling for the parents, and identifies neurodevelopmental and psychiatric risks long before they would otherwise be visible.

genetic testing NCIT:C15709

Show evidence (2 references)

PMID:32049433 SUPPORT Human Clinical

"New guidelines suggest screening for a 22q11.2 deletion in the patient with tetralogy of Fallot, truncus arteriosus, interrupted aortic arch type B, conoventricular septal defects as well as those with an isolated aortic arch anomaly."

Names truncus arteriosus explicitly as a guideline-level indication for deletion testing.

PMID:32049433 SUPPORT Human Clinical

"Early identification of a 22q11.2 deletion in the neonate or infant when other syndromic features may not be apparent allows for timely parental screening for reproductive counseling and anticipatory evaluation of cardiac and noncardiac features."

States why testing should not wait for syndromic features to declare themselves.

Whole-genome or whole-exome sequencing in deletion-negative cases

Sequencing has real yield in patients without the deletion. In a Japanese series of 11 deletion-negative patients, five carried pathogenic TMEM260 variants and two more carried de novo variants in GATA6 and NOTCH1, so a majority of the cohort received a molecular diagnosis. The yield is population-dependent, since the TMEM260 signal rests on a local founder variant, which is itself an argument for sequencing rather than for targeted panels built elsewhere.

whole genome sequencing NCIT:C101294

Show evidence (1 reference)

PMID:38351237 SUPPORT Human Clinical

"We performed whole-genome sequencing of 11 Japanese patients having TA without 22q11.2 deletion. Among five patients, we identified pathogenic variants in TMEM260"

Demonstrates the diagnostic yield of sequencing in deletion-negative patients.

Genetic counselling

Follows from the genetic result and is a distinct clinical action. Counselling differs sharply by mechanism: a de novo 22q11.2 deletion carries low recurrence risk but a fifty percent transmission risk for the affected child, whereas biallelic TMEM260 disease is autosomal recessive with a one in four sibling recurrence risk and identifiable carrier parents.

genetic counseling NCIT:C15240

Show evidence (1 reference)

PMID:32049433 SUPPORT Human Clinical

"allows for timely parental screening for reproductive counseling and anticipatory evaluation of cardiac and noncardiac features"

States the reproductive-counselling purpose that the genetic diagnosis serves.

📈

Progression

4

Fetal and immediate newborn period

The lesion is fully formed by week eight of gestation and is well tolerated in utero, because the fetal circulation is already a parallel mixing circuit. At birth, high neonatal pulmonary vascular resistance still limits pulmonary flow, so the infant may look deceptively well. Increasingly the diagnosis is made antenatally or by newborn pulse oximetry rather than by clinical deterioration.

Neonatal decompensation

Over the first days to weeks pulmonary vascular resistance falls physiologically, pulmonary blood flow rises steeply, and the infant develops high-output heart failure. This is when repair is performed, and the window is narrow. Contemporary in-hospital mortality around repair is about 10.8 percent, with prematurity, stroke, necrotising enterocolitis, and venous thrombosis as independent risk factors.

Show evidence (2 references)

PMID:32557823 SUPPORT Human Clinical

"Overall, 3009 neonates met inclusion criteria; a total of 326 patients died during the hospitalization (10.8%)."

Contemporary national in-hospital mortality across 3009 neonates.

PMID:32557823 SUPPORT Human Clinical

"necrotizing enterocolitis (aOR = 3.10; 95% CI: 1.24-7.74; P = .015) and presence of venous thrombosis (aOR = 13.5; 95% CI: 6.7-27.2; P < .001)"

Gives two of the independent mortality risk factors with their adjusted odds ratios in the same cohort.

Untreated progression to fixed pulmonary vascular disease

Without repair, sustained systemic-pressure pulmonary flow produces irreversible pulmonary vascular obstructive disease within the first year or two, converting an operable lesion into an inoperable one. This is the natural history that neonatal repair exists to pre-empt, and it is why deferring surgery is not a conservative option here.

Show evidence (1 reference)

PMID:38884754 SUPPORT Human Clinical

"a single common outflow vessel persists resulting in a serious clinical condition known as persistent truncus arteriosus or common arterial trunk"

Characterises the unrepaired lesion as a serious condition; PARTIAL because the specific pulmonary vascular endpoint is not described.

Post-repair surveillance and reintervention

Repair is not a cure but a conversion into a different chronic problem. The right ventricle to pulmonary artery conduit is fixed in size while the child is not, so it is outgrown and must be replaced serially through childhood and adolescence. Truncal valve regurgitation frequently progresses and drives further reoperation independently of the conduit.

📊

Prevalence

2

Critical congenital heart disease

Point Prevalence Rare

Truncus arteriosus accounts for about 4 percent of all critical congenital heart disease, the subset requiring intervention in the newborn period. This is a share of a diagnostic category rather than a population rate, and is recorded as such.

Show evidence (1 reference)

PMID:38351237 SUPPORT Human Clinical

"TA accounts for 4% of all critical congenital heart diseases."

The share of critical congenital heart disease attributable to this lesion.

22q11.2 deletion syndrome, livebirths

Birth Prevalence 20.0 per 100,000 1–9 per 10,000

The deletion syndrome that causes 12 to 35 percent of truncus arteriosus has an estimated prevalence of 1 in 4000 to 6000 livebirths, with 60 to 80 percent of those having a cardiac malformation. Recorded here as denominator context for the leading genetic cause, not as the prevalence of this malformation.

Show evidence (2 references)

PMID:32049433 SUPPORT Human Clinical

"The 22q11.2 deletion syndrome has an estimated prevalence of 1 in 4-6,000 livebirths."

Birth prevalence of the deletion syndrome.

PMID:32049433 SUPPORT Human Clinical

"Approximately 60-80% of patients have a cardiac malformation most commonly including a subset of conotruncal defects"

The cardiac penetrance of the deletion, which converts its birth prevalence into a conotruncal-disease denominator.

⚖️

Clinical Burden

High

A critical congenital heart lesion that is uniformly fatal in infancy without surgery, and whose surgical treatment still carries about 10.8 percent in-hospital mortality in contemporary national data. Repair is not curative: the right ventricle to pulmonary artery conduit is outgrown and must be replaced serially through childhood, and truncal valve regurgitation drives further reoperation, so survivors carry a lifelong surgical and surveillance burden.

A substantial minority carry a 22q11.2 deletion, which adds hypocalcaemia, immunodeficiency, palatal and feeding disorders, and neurodevelopmental and psychiatric morbidity to the cardiac disease. Those patients have more perioperative complications than non-syndromic patients but do not, in the reported data, have higher surgical mortality, so the syndromic burden is chiefly a matter of complication management and lifelong non-cardiac care rather than of operative survival.

Show evidence (2 references)

PMID:32557823 SUPPORT Human Clinical

"Overall, 3009 neonates met inclusion criteria; a total of 326 patients died during the hospitalization (10.8%)."

Contemporary in-hospital mortality in a national neonatal cohort.

PMID:32049433 SUPPORT Human Clinical

"Cardiac patients with a 22q11.2 deletion do not generally experience higher mortality upon surgical intervention but suffer more peri-operative complications than their non-syndromic counterparts."

Separates the syndromic complication burden from operative mortality, which is the distinction the notes above rest on.

🔀

Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from Persistent Truncus Arteriosus:

Tetralogy of Fallot with pulmonary atresia

Overlapping Features The closest anatomic mimic, and separating them is consequential rather than academic. Both can present as a ventricular septal defect with a single visible outflow vessel. The distinction is whether pulmonary arteries arise from that vessel, as they do in truncus, or are supplied through a duct or aortopulmonary collaterals, as in pulmonary atresia. Physiology follows anatomy in opposite directions: truncus floods the lungs and needs pulmonary flow restricted, whereas pulmonary atresia starves them and needs the duct kept open with prostaglandin.

Show evidence (1 reference)

PMID:32049433 SUPPORT Human Clinical

"a subset of conotruncal defects (tetralogy of Fallot, truncus arteriosus, interrupted aortic arch type B)"

Places the two lesions in the same conotruncal family sharing a genetic cause; PARTIAL because the source does not address their differentiation.

Aortopulmonary window

Overlapping Features Also produces a communication between aorta and pulmonary artery with pulmonary overcirculation, but the semilunar valves are two and separate, and the ventricular septum is usually intact. The count of semilunar valves is the discriminating observation on echocardiography.

Show evidence (1 reference)

PMID:15649947 SUPPORT Human Clinical

"A common arterial trunk (CAT) is often diagnosed as PTA in the absence of evidence of embryological mechanism."

Notes explicitly that the diagnostic label is applied on appearance without embryologic confirmation, which is the reasoning gap this differential exploits; PARTIAL because aortopulmonary window is not named.

Structural heart defects and renal anomalies syndrome

Overlapping Features Not a competing cardiac diagnosis but a syndromic context that changes what else to look for. Biallelic TMEM260 loss of function produces this syndrome, so an infant with truncus arteriosus and no 22q11.2 deletion warrants renal imaging, and the recurrence counselling is recessive rather than de novo.

Show evidence (1 reference)

PMID:38351237 SUPPORT Human Clinical

"the biallelic loss-of-function variants of which have recently been associated with structural heart defects and renal anomalies syndrome (SHDRA)"

Links the genetic finding to the extracardiac syndrome that should then be evaluated.

🧫

Experimental Models

2

Splotch mutant mouse OTHER

The founding genetic model, and the experiment that established the cardiac neural crest as the tissue of origin for this malformation. Homozygous Sp1H mutants fail to septate the truncus arteriosus and develop persistent truncus arteriosus with an ostium opening to the right ventricle, together with aortic arch variants and thymic, parathyroid, and ultimobranchial body defects. That pattern is the point: the same mutation affects every structure the neural crest populates, which is the argument that the cardiac lesion is a neurocristopathy rather than a local septation failure. The model dies mid-gestation, so it cannot address postnatal physiology at all.

Organism

house mouse NCBITaxon:10090

Publication

PMID:2619088

Pathograph links

Cardiac neural crest and second heart field program disruption Splotch disrupts neural-crest-derived cell populations, which is the trigger node here.

Failure of aorticopulmonary septation The mutant reproduces the septation failure itself.

Show evidence (3 references)

PMID:2619088 SUPPORT Model Organism

"It is shown that in homozygous mutant embryos, the septation of the truncus arteriosus does not proceed normally, resulting in persistent truncus arteriosus."

Direct recapitulation of the human malformation from a neural crest defect.

PMID:2619088 SUPPORT Model Organism

"These results provide indirect evidence, that cells contributing to the aortic arches and the septum of the truncus arteriosus in mice are derived from the neural crest."

The inference that makes this model mechanistically informative rather than merely phenocopying, and the basis for the trigger node in this entry.

PMID:2619088 SUPPORT Model Organism

"The development of the thymus, the parathyroid and the ultimobranchial bodies are also variably affected in mutants."

The extracardiac involvement that parallels the 22q11.2 phenotype in humans and supports a shared pharyngeal and neural-crest origin.

Tbx1 conditional null mouse with beta-catenin dosage rescue OTHER

The canonical model for the 22q11.2 route, and the one that identifies the molecular error. Inactivating Tbx1 in anterior heart field mesoderm produces premature expression of pro-differentiation genes and a persistent truncus arteriosus, so the defect is one of developmental timing rather than of cell absence. Removing one allele of beta-catenin rescues the outflow tract defect in 61 percent of double mutants, which establishes an antagonistic relationship between the two pathways and shows the malformation is developmentally reversible in principle. That is the closest thing to a mechanistic target this disease has.

Organism

house mouse NCBITaxon:10090

Publication

PMID:28346476

Pathograph links

Cardiac neural crest and second heart field program disruption Tbx1 inactivation in anterior heart field mesoderm models the second heart field arm of the trigger node, complementing the neural crest arm modelled by Splotch.

Failure of aorticopulmonary septation The mutant reproduces the failure of septation between aorta and pulmonary trunk.

Show evidence (2 references)

PMID:28346476 SUPPORT Model Organism

"Inactivation of Tbx1 in the anterior heart field (AHF) mesoderm in the mouse results in premature expression of pro-differentiation genes and a persistent truncus arteriosus (PTA) in which septation does not form between the aorta and pulmonary trunk."

States both the phenotype and the molecular error behind it, premature differentiation rather than loss of the progenitor population.

PMID:28346476 SUPPORT Model Organism

"When both alleles of Tbx1 and one allele of β-catenin were inactivated in the Mef2c-AHF-Cre domain, 61% of them (n = 34) showed partial or complete rescue of the PTA defect."

The genetic rescue, which is the strongest evidence that this is a dosage-sensitive signalling imbalance rather than an irrecoverable structural loss.

{ }

Source YAML

click to show

name: Persistent Truncus Arteriosus
creation_date: '2026-08-09T00:00:00Z'
category: Congenital
description: >
  Persistent truncus arteriosus, or common arterial trunk, is a cyanotic conotruncal
  malformation in which the embryonic outflow tract fails to septate, so a single arterial
  trunk arises from the heart through one semilunar valve, overrides a ventricular septal
  defect, and supplies the coronary, pulmonary, and systemic circulations from a common
  source. It is a defect of the cardiac neural crest and second heart field developmental
  unit, and 22q11.2 deletion syndrome is its single largest identified cause. The postnatal
  physiology is dictated by what the anatomy does not do: because there is no pulmonary
  outflow obstruction, pulmonary blood flow is set entirely by the ratio of pulmonary to
  systemic vascular resistance, so as pulmonary resistance falls in the first days of life
  the lungs are flooded at systemic pressure. The newborn is therefore mildly cyanosed but
  in high-output heart failure, and the untreated course runs to irreversible pulmonary
  vascular obstructive disease within the first year or two, at which point repair becomes
  impossible. Neonatal surgical repair, closing the ventricular septal defect and
  interposing a right ventricle to pulmonary artery conduit, is the standard of care, and
  the conduit must then be replaced repeatedly as the child grows.
disease_term:
  preferred_term: persistent truncus arteriosus
  term:
    id: MONDO:0018072
    label: persistent truncus arteriosus
parents:
- Congenital heart defect
- Conotruncal malformation
synonyms:
- Truncus arteriosus communis
- Common arterial trunk
- Truncus arteriosus
pathophysiology:
- name: Cardiac neural crest and second heart field program disruption
  description: >
    The outflow tract is built by two cell populations acting together: cardiac neural crest
    cells migrating through pharyngeal arches three, four, and six to form the elastogenic
    smooth muscle of the aorticopulmonary septum, and second heart field mesoderm adding
    myocardium to the elongating outflow tract. Their crosstalk is patterned by TBX, GATA,
    and NKX transcription factors and by FGF, BMP, and Wnt signalling. Disruption anywhere
    in this unit, whether by 22q11.2 deletion, a monogenic variant, or a teratogen, converges
    on the same failure.
  biological_scale: CELLULAR
  role: trigger
  cell_types:
  - preferred_term: Cardiac neural crest cell
    term:
      id: CL:0011012
      label: neural crest cell
  biological_processes:
  - preferred_term: cardiac neural crest cell development involved in outflow tract morphogenesis
    term:
      id: GO:0061309
      label: cardiac neural crest cell development involved in outflow tract morphogenesis
    modifier: DECREASED
  - preferred_term: neural crest cell migration
    term:
      id: GO:0001755
      label: neural crest cell migration
    modifier: DECREASED
  locations:
  - preferred_term: Outflow tract
    term:
      id: UBERON:0004145
      label: outflow tract
  downstream:
  - target: Failure of aorticopulmonary septation
    causal_link_type: DIRECT
    description: >
      Without a properly specified and positioned neural-crest-derived septal population, the
      conotruncal ridges do not fuse and no aorticopulmonary septum forms.
    evidence:
    - reference: PMID:38884754
      reference_title: "Molecular Pathways and Animal Models of Truncus Arteriosus."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "we will review molecular pathways and the cells that are known to play a role in the formation and development of the outflow tract and how genetic manipulation of these pathways in animal models can result in common arterial trunk"
      explanation: States that genetic manipulation of the outflow-tract developmental pathways in animal models reproduces the human malformation, which is the evidence that this cellular program is the causal locus.
  evidence:
  - reference: PMID:38884753
    reference_title: "Human Genetics of Truncus Arteriosus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other congenital malformation syndromes and variants in genes encoding TBX, GATA, and NKX transcription factors and some signaling proteins have also been reported as its etiology."
    explanation: Identifies the transcription-factor families whose disruption produces the malformation, which is what makes this a developmental-program defect rather than a single-gene disease.
- name: Failure of aorticopulmonary septation
  description: >
    The defining embryologic event, occurring in weeks five to eight of human gestation. The
    conotruncal ridges fail to fuse and spiral, so no aorticopulmonary septum divides the
    common trunk into aorta and pulmonary trunk. The same septal deficiency accounts for the
    ventricular septal defect, because the conal septum that would have closed the outflow
    portion of the interventricular septum is absent or malformed. That is why the ventricular
    septal defect here is not an independent second lesion but part of the same failure.
  biological_scale: TISSUE
  role: mechanism
  biological_processes:
  - preferred_term: outflow tract septum morphogenesis
    term:
      id: GO:0003148
      label: outflow tract septum morphogenesis
    modifier: LOSS_OF_FUNCTION
  locations:
  - preferred_term: Truncus arteriosus
    term:
      id: UBERON:0002061
      label: truncus arteriosus
  - preferred_term: Outflow tract septum
    term:
      id: UBERON:0004142
      label: outflow tract septum
  downstream:
  - target: Single arterial trunk overriding a ventricular septal defect
    causal_link_type: DIRECT
    description: >
      The unseptated trunk persists as a single vessel with one semilunar valve, sitting over
      the unclosed outflow portion of the interventricular septum.
    evidence:
    - reference: PMID:15649947
      reference_title: "Common arterial trunk associated with a homeodomain mutation of NKX2.6."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Persistent truncus arteriosus (PTA) is a failure of septation of the cardiac outflow tract (OFT) into the pulmonary artery and the aorta."
      explanation: Defines the malformation as the direct structural consequence of the septation failure.
  evidence:
  - reference: PMID:38884754
    reference_title: "Molecular Pathways and Animal Models of Truncus Arteriosus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "When the process of outflow tract septation fails, a single common outflow vessel persists resulting in a serious clinical condition known as persistent truncus arteriosus or common arterial trunk."
    explanation: States the septation-failure-to-single-vessel step as the definition of the disease.
- name: Single arterial trunk overriding a ventricular septal defect
  description: >
    The anatomic result. One vessel leaves the heart through a single semilunar valve and
    gives rise to the coronary arteries, the pulmonary arteries, and the systemic
    circulation. Because both ventricles eject into it across a large non-restrictive
    ventricular septal defect, systemic and pulmonary venous return mix obligatorily at the
    trunk, and both ventricles see systemic pressure.
  biological_scale: ORGANISM
  role: mechanism
  locations:
  - preferred_term: Interventricular septum
    term:
      id: UBERON:0002094
      label: interventricular septum
  downstream:
  - target: Obligatory mixing of systemic and pulmonary venous return
    causal_link_type: DIRECT
    description: >
      A single outlet for both ventricles forces complete admixture of oxygenated and
      deoxygenated blood.
    evidence:
    - reference: PMID:38351237
      reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Truncus Arteriosus (TA) is a congenital heart disease characterized by a single common blood vessel emerging from the right and left ventricles instead of the main pulmonary artery and aorta."
      explanation: States that the single vessel receives ejection from both ventricles, which is what makes the mixing obligatory rather than shunt-dependent.
  - target: Unobstructed pulmonary blood flow at systemic pressure
    causal_link_type: DIRECT
    description: >
      Pulmonary arteries arising directly from the trunk are exposed to systemic pressure
      with no interposed obstruction.
    evidence:
    - reference: PMID:15649947
      reference_title: "Common arterial trunk associated with a homeodomain mutation of NKX2.6."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "a failure of septation of the cardiac outflow tract (OFT) into the pulmonary artery and the aorta"
      explanation: Establishes that the pulmonary arteries and aorta share a single unseptated source; PARTIAL because the haemodynamic consequence is not stated in the source.
  - target: Truncal valve dysfunction
    causal_link_type: DIRECT
    description: >
      The single semilunar valve is frequently dysplastic, with an abnormal cusp number, and
      is prone to regurgitation and, less often, stenosis.
  - target: Coronary ostial anomaly
    causal_link_type: DIRECT
    description: >
      Coronary arteries arise from an abnormal single-trunk root rather than from a normally
      septated aortic sinus template, so their origins are frequently anomalous.
    evidence:
    - reference: PMID:38351237
      reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "a single common blood vessel emerging from the right and left ventricles instead of the main pulmonary artery and aorta"
      explanation: Establishes the abnormal root geometry from which the coronaries must arise; PARTIAL because the coronary consequence is not asserted in the source.
  evidence:
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Truncus Arteriosus (TA) is a congenital heart disease characterized by a single common blood vessel emerging from the right and left ventricles instead of the main pulmonary artery and aorta."
    explanation: The definitional statement of this node, naming the single vessel and the fact that it receives ejection from both ventricles.
- name: Obligatory mixing of systemic and pulmonary venous return
  description: >
    Because there is one outlet, mixing is complete and is not modulated by shunt size or
    direction. Arterial saturation is therefore set by the proportion of pulmonary to systemic
    flow rather than by any restrictive orifice, which has a counterintuitive consequence:
    the more the lungs are flooded, the pinker the baby looks, so improving colour in an
    untreated infant is a sign of worsening physiology rather than improvement.
  biological_scale: ORGANISM
  role: mechanism
  downstream:
  - target: Cyanosis
    causal_link_type: DIRECT
    description: >
      Admixture of desaturated systemic venous return lowers arterial oxygen saturation.
  evidence:
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a single common blood vessel emerging from the right and left ventricles"
    explanation: The single common outlet from both ventricles is the anatomic basis of obligatory mixing.
- name: Unobstructed pulmonary blood flow at systemic pressure
  description: >
    In most anatomic subtypes nothing restricts flow into the pulmonary arteries. The
    pulmonary bed therefore sees systemic pressure directly, and pulmonary blood flow is
    governed purely by the ratio of pulmonary to systemic vascular resistance. In the first
    hours of life high neonatal pulmonary resistance masks the problem; over the following
    days that resistance falls physiologically, flow rises steeply, and the infant
    decompensates. The clinical corollary is that a well-looking newborn with this lesion is
    not reassuring, merely early.
  biological_scale: ORGANISM
  role: mechanism
  locations:
  - preferred_term: Pulmonary artery
    term:
      id: UBERON:0002012
      label: pulmonary artery
  downstream:
  - target: Pulmonary overcirculation and volume-overload heart failure
    causal_link_type: DIRECT
    description: >
      As pulmonary vascular resistance falls after birth, pulmonary blood flow rises and
      volume-loads the ventricles.
  - target: Pulmonary vascular obstructive disease
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >
      Sustained high-flow, high-pressure exposure of the pulmonary bed drives progressive
      remodelling toward fixed resistance.
  evidence:
  - reference: PMID:38884754
    reference_title: "Molecular Pathways and Animal Models of Truncus Arteriosus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the outflow tract of the heart is divided into two distinct channels to separate the oxygenated systemic blood flow from the deoxygenated pulmonary circulation"
    explanation: States the function of normal septation, whose absence leaves the pulmonary circulation exposed to systemic pressure.
- name: Truncal valve dysfunction
  description: >
    The single semilunar valve is frequently abnormal, with two, three, four, or rarely five
    cusps, and is often dysplastic. Regurgitation adds volume load on top of the pulmonary
    overcirculation. Stenosis is less common but worse tolerated, because both ventricles
    eject through this one valve, so a single stenotic orifice imposes pressure load on the
    whole heart at once. Truncal valve disease is a principal determinant of both operative
    difficulty and long-term reoperation.
  biological_scale: TISSUE
  role: mechanism
  downstream:
  - target: Pulmonary overcirculation and volume-overload heart failure
    causal_link_type: DIRECT
    description: >
      Truncal regurgitation adds regurgitant volume to the already high pulmonary flow,
      compounding ventricular volume overload.
  evidence:
  - reference: PMID:837493
    reference_title: "Coronary arterial origin in persistent truncus arteriosus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Bicuspid truncal valve was observed in six cases (20%) and tricuspid in 21 cases (70%)."
    explanation: Autopsy series of 30 hearts quantifying truncal valve cusp number, which is the morphological abnormality this node asserts.
- name: Coronary ostial anomaly
  description: >
    Coronary origins are abnormal in a large fraction of cases, because the coronary buds
    address a single unseptated root rather than the normal paired aortic sinuses. There is
    no single consistent pattern, which is precisely the problem: the surgeon must map the
    coronaries individually before repair, and an unrecognised anomalous course is an
    independent driver of perioperative mortality.
  biological_scale: TISSUE
  role: mechanism
  downstream:
  - target: Perioperative myocardial ischaemia
    causal_link_type: DIRECT
    description: >
      An anomalous coronary origin or course can be compressed, distorted, or divided during
      conduit placement and root reconstruction.
    evidence:
    - reference: PMID:32557823
      reference_title: "Outcomes of truncus arteriosus repair and predictors of mortality."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "a total of 326 patients died during the hospitalization (10.8%)"
      explanation: Quantifies the in-hospital mortality that coronary anomalies contribute to; PARTIAL because the database analysis does not attribute deaths to coronary anatomy.
  evidence:
  - reference: PMID:837493
    reference_title: "Coronary arterial origin in persistent truncus arteriosus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There was a strong tendency for the left coronary artery to arise from a more posterior level than it does normally from the aorta."
    explanation: Documents the systematic displacement of the coronary origin from its normal aortic position, which is the consequence of the trunk not having septated into a normal aortic root.
  - reference: PMID:837493
    reference_title: "Coronary arterial origin in persistent truncus arteriosus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Single coronary artery was observed in four cases (three with tricuspid and one with quadricuspid truncal valves)."
    explanation: Quantifies the most surgically consequential variant, a single coronary artery, in four of 30 hearts.
- name: Pulmonary overcirculation and volume-overload heart failure
  description: >
    The clinical presentation in the first weeks: tachypnoea, poor feeding, sweating,
    failure to thrive, and hepatomegaly, in an infant who is only mildly desaturated. It is
    high-output failure from excessive pulmonary blood flow, not pump failure, which is why
    the treatment before surgery is to limit pulmonary flow rather than to augment
    contractility.
  biological_scale: ORGANISM
  role: consequence
  downstream:
  - target: Pulmonary vascular obstructive disease
    causal_link_type: DIRECT
    description: >
      Continuing high-flow high-pressure exposure remodels the pulmonary arterioles.
- name: Pulmonary vascular obstructive disease
  description: >
    The end of the untreated natural history, and the reason this is a neonatal surgical
    disease rather than an elective one. Sustained exposure of the pulmonary bed to systemic
    pressure and high flow produces fixed obstructive remodelling within the first year or
    two of life. Once resistance is fixed, closing the ventricular septal defect is
    contraindicated for the same reason it is in Eisenmenger physiology, and the operation
    that would have been curative at two weeks becomes lethal.
  biological_scale: ORGANISM
  role: consequence
  conforms_to: "pulmonary_vascular_remodeling#Obstructive Pulmonary Vascular Remodeling"
  locations:
  - preferred_term: Pulmonary artery
    term:
      id: UBERON:0002012
      label: pulmonary artery
- name: Perioperative myocardial ischaemia
  description: >
    Ischaemic injury around the time of repair, from anomalous coronary anatomy, from
    coronary distortion during root reconstruction, or from the mismatch between a
    volume-loaded ventricle and a diastolic pressure lowered by truncal regurgitation. It is
    one of the mechanisms behind an in-hospital mortality that remains around one in ten even
    in the contemporary era.
  biological_scale: ORGANISM
  role: consequence
  evidence:
  - reference: PMID:32557823
    reference_title: "Outcomes of truncus arteriosus repair and predictors of mortality."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Overall, 3009 neonates met inclusion criteria; a total of 326 patients died during the hospitalization (10.8%)."
    explanation: Quantifies contemporary in-hospital mortality in a national cohort; PARTIAL because ischaemia is not separately attributed.
- name: Cyanosis
  description: >
    Present from birth but characteristically mild, because pulmonary blood flow is high.
    This is why the lesion is easy to miss on inspection and why newborn pulse-oximetry
    screening matters more here than a visual assessment does.
  biological_scale: ORGANISM
  role: consequence
phenotypes:
- category: Clinical
  name: Truncus arteriosus
  description: >
    The defining malformation: a single arterial trunk with one semilunar valve giving rise
    to the coronary, pulmonary, and systemic circulations.
  phenotype_term:
    preferred_term: Truncus arteriosus
    term:
      id: HP:0001660
      label: Truncus arteriosus
  frequency: OBLIGATE
  evidence:
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Truncus Arteriosus (TA) is a congenital heart disease characterized by a single common blood vessel emerging from the right and left ventricles instead of the main pulmonary artery and aorta."
    explanation: The obligate defining anatomy.
- category: Clinical
  name: Ventricular septal defect
  description: >
    Large and non-restrictive, part of the same septation failure rather than an independent
    lesion, and the reason both ventricles eject into the common trunk.
  phenotype_term:
    preferred_term: Ventricular septal defect
    term:
      id: HP:0001629
      label: Ventricular septal defect
  frequency: OBLIGATE
  evidence:
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a single common blood vessel emerging from the right and left ventricles"
    explanation: The trunk receiving ejection from both ventricles entails the septal defect that lets it do so.
- category: Clinical
  name: Cyanosis
  description: >
    Mild central cyanosis from birth, reflecting obligatory mixing rather than restricted
    pulmonary flow.
  phenotype_term:
    preferred_term: Cyanosis
    term:
      id: HP:0000961
      label: Cyanosis
    temporality: CHRONIC
  frequency: VERY_FREQUENT
- category: Clinical
  name: Congestive heart failure
  description: >
    High-output failure developing over the first days to weeks as pulmonary vascular
    resistance falls, with tachypnoea, sweating, and hepatomegaly.
  phenotype_term:
    preferred_term: Congestive heart failure
    term:
      id: HP:0001635
      label: Congestive heart failure
    temporality: ACUTE
  frequency: VERY_FREQUENT
- category: Symptom
  name: Tachypnea
  description: >
    Driven by pulmonary overcirculation and interstitial congestion, and typically the first
    thing a parent notices.
  phenotype_term:
    preferred_term: Tachypnea
    term:
      id: HP:0002789
      label: Tachypnea
  frequency: FREQUENT
- category: Clinical
  name: Failure to thrive
  description: >
    Poor feeding against a high metabolic demand from the volume-overloaded circulation,
    which is one of the arguments for early rather than deferred repair.
  phenotype_term:
    preferred_term: Failure to thrive
    term:
      id: HP:0001508
      label: Failure to thrive
    clinical_course: PROGRESSIVE
  frequency: FREQUENT
- category: Clinical
  name: Aortic regurgitation
  description: >
    Truncal valve regurgitation, curated against the aortic regurgitation term because the
    truncal valve is the common semilunar valve from which the aortic valve would have
    formed. Present in roughly half of patients and a principal driver of ventricular volume
    load and of late reoperation.
  phenotype_term:
    preferred_term: Truncal valve regurgitation
    term:
      id: HP:0001659
      label: Aortic regurgitation
  frequency: FREQUENT
  evidence:
  - reference: PMID:837493
    reference_title: "Coronary arterial origin in persistent truncus arteriosus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Bicuspid truncal valve was observed in six cases (20%) and tricuspid in 21 cases (70%)."
    explanation: Establishes the abnormal cusp anatomy that predisposes to regurgitation; PARTIAL because the series reports valve morphology at autopsy and not the presence or severity of regurgitation in life.
- category: Clinical
  name: Abnormal coronary artery origin
  description: >
    Anomalous coronary ostial position or course, frequent and without a consistent pattern,
    and an independent contributor to operative risk.
  phenotype_term:
    preferred_term: Abnormal coronary artery origin
    term:
      id: HP:0011636
      label: Abnormal coronary artery origin
  frequency: FREQUENT
  evidence:
  - reference: PMID:837493
    reference_title: "Coronary arterial origin in persistent truncus arteriosus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Specimens of heart from 30 subjects with persistent truncus arteriosus were studied for the nature and sites of coronary arterial origin."
    explanation: The autopsy series that characterised coronary origin in this malformation.
  - reference: PMID:837493
    reference_title: "Coronary arterial origin in persistent truncus arteriosus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "It was common for the posterior descending artery to arise from the left circumflex artery. This arrangement was noted in eight of 25 cases (32%)"
    explanation: A specific anomalous arrangement in 32 percent of cases, supporting the FREQUENT band with a counted denominator rather than a review estimate.
- category: Clinical
  name: Right aortic arch
  description: >
    A right-sided aortic arch accompanies the malformation in a substantial minority. It is an
    arch-patterning anomaly rather than a consequence of the septation failure, which is
    consistent with both arising from the same disrupted neural crest and pharyngeal arch
    program. No frequency band is curated: the cited source is a five-patient case series and
    reports the finding in one patient, which establishes the association but cannot support a
    rate.
  phenotype_term:
    preferred_term: Right aortic arch
    term:
      id: HP:0012020
      label: Right aortic arch
  evidence:
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "right aortic arch (RAA) in Patient 2"
    explanation: Documents a right aortic arch in a patient in this truncus arteriosus case series, which establishes the association without supporting any particular rate.
- category: Clinical
  name: Interrupted aortic arch
  description: >
    Defines Van Praagh type A4 and is one of the anomalies shared with the wider 22q11.2
    conotruncal spectrum, which is part of why the deletion should be sought in any infant
    with either lesion.
  phenotype_term:
    preferred_term: Interrupted aortic arch
    term:
      id: HP:0011611
      label: Interrupted aortic arch
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:32049433
    reference_title: "22q11.2 deletion syndrome and congenital heart disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a subset of conotruncal defects (tetralogy of Fallot, truncus arteriosus, interrupted aortic arch type B), conoventricular and/or atrial septal defects, and aortic arch anomalies"
    explanation: Places truncus arteriosus and interrupted aortic arch together within the same 22q11.2 conotruncal spectrum.
- category: Clinical
  name: Pulmonary arterial hypertension
  description: >
    The consequence of leaving the pulmonary bed exposed to systemic pressure, and the
    finding that closes the surgical window once it becomes fixed.
  phenotype_term:
    preferred_term: Pulmonary arterial hypertension
    term:
      id: HP:0002092
      label: Pulmonary arterial hypertension
    clinical_course: PROGRESSIVE
  frequency: FREQUENT
  evidence:
  - reference: PMID:38884754
    reference_title: "Molecular Pathways and Animal Models of Truncus Arteriosus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the outflow tract of the heart is divided into two distinct channels to separate the oxygenated systemic blood flow from the deoxygenated pulmonary circulation"
    explanation: States the separation that normally protects the pulmonary circulation from systemic pressure, whose absence produces pulmonary hypertension; PARTIAL because the complication is not described in the source.
- category: Laboratory
  name: Hypocalcemia
  description: >
    Neonatal hypocalcaemia from parathyroid hypoplasia in the 22q11.2-deleted subgroup. It
    is worth checking specifically in a truncus neonate, because hypocalcaemia is
    perioperatively consequential and because it points at the deletion.
  phenotype_term:
    preferred_term: Hypocalcemia
    term:
      id: HP:0002901
      label: Hypocalcemia
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:32049433
    reference_title: "22q11.2 deletion syndrome and congenital heart disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the most common features include: facial dysmorphia, hypocalcemia, palate and speech disorders, feeding and gastrointestinal disorders, immunodeficiency, recurrent infections, neurodevelopmental and psychiatric disorders, and congenital heart disease"
    explanation: Lists hypocalcaemia among the core features of the syndrome present in a substantial minority of these infants.
progression:
- phase: Fetal and immediate newborn period
  notes: >
    The lesion is fully formed by week eight of gestation and is well tolerated in utero,
    because the fetal circulation is already a parallel mixing circuit. At birth, high
    neonatal pulmonary vascular resistance still limits pulmonary flow, so the infant may
    look deceptively well. Increasingly the diagnosis is made antenatally or by newborn pulse
    oximetry rather than by clinical deterioration.
- phase: Neonatal decompensation
  notes: >
    Over the first days to weeks pulmonary vascular resistance falls physiologically,
    pulmonary blood flow rises steeply, and the infant develops high-output heart failure.
    This is when repair is performed, and the window is narrow. Contemporary in-hospital
    mortality around repair is about 10.8 percent, with prematurity, stroke, necrotising
    enterocolitis, and venous thrombosis as independent risk factors.
  evidence:
  - reference: PMID:32557823
    reference_title: "Outcomes of truncus arteriosus repair and predictors of mortality."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Overall, 3009 neonates met inclusion criteria; a total of 326 patients died during the hospitalization (10.8%)."
    explanation: Contemporary national in-hospital mortality across 3009 neonates.
  - reference: PMID:32557823
    reference_title: "Outcomes of truncus arteriosus repair and predictors of mortality."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "necrotizing enterocolitis (aOR = 3.10; 95% CI: 1.24-7.74; P = .015) and presence of venous thrombosis (aOR = 13.5; 95% CI: 6.7-27.2; P < .001)"
    explanation: Gives two of the independent mortality risk factors with their adjusted odds ratios in the same cohort.
- phase: Untreated progression to fixed pulmonary vascular disease
  notes: >
    Without repair, sustained systemic-pressure pulmonary flow produces irreversible
    pulmonary vascular obstructive disease within the first year or two, converting an
    operable lesion into an inoperable one. This is the natural history that neonatal repair
    exists to pre-empt, and it is why deferring surgery is not a conservative option here.
  evidence:
  - reference: PMID:38884754
    reference_title: "Molecular Pathways and Animal Models of Truncus Arteriosus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a single common outflow vessel persists resulting in a serious clinical condition known as persistent truncus arteriosus or common arterial trunk"
    explanation: Characterises the unrepaired lesion as a serious condition; PARTIAL because the specific pulmonary vascular endpoint is not described.
- phase: Post-repair surveillance and reintervention
  notes: >
    Repair is not a cure but a conversion into a different chronic problem. The right
    ventricle to pulmonary artery conduit is fixed in size while the child is not, so it is
    outgrown and must be replaced serially through childhood and adolescence. Truncal valve
    regurgitation frequently progresses and drives further reoperation independently of the
    conduit.
diagnosis:
- name: Transthoracic echocardiography
  description: >
    The diagnostic test. It demonstrates the single trunk overriding the ventricular septal
    defect, the number and competence of the truncal valve cusps, the origin pattern of the
    pulmonary arteries that determines the anatomic subtype, and any arch anomaly. It is also
    the test that must be complete before surgery, because the operative plan depends on
    these details.
  diagnosis_term:
    preferred_term: echocardiography
    term:
      id: NCIT:C16525
      label: Echocardiography Test
- name: 22q11.2 deletion testing
  description: >
    Should be performed in every infant with this diagnosis, not only in those who look
    syndromic. Guidelines specifically name truncus arteriosus as an indication, and the
    reason is practical: the deletion changes perioperative management through hypocalcaemia
    and immunodeficiency, changes recurrence counselling for the parents, and identifies
    neurodevelopmental and psychiatric risks long before they would otherwise be visible.
  diagnosis_term:
    preferred_term: genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: PMID:32049433
    reference_title: "22q11.2 deletion syndrome and congenital heart disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "New guidelines suggest screening for a 22q11.2 deletion in the patient with tetralogy of Fallot, truncus arteriosus, interrupted aortic arch type B, conoventricular septal defects as well as those with an isolated aortic arch anomaly."
    explanation: Names truncus arteriosus explicitly as a guideline-level indication for deletion testing.
  - reference: PMID:32049433
    reference_title: "22q11.2 deletion syndrome and congenital heart disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Early identification of a 22q11.2 deletion in the neonate or infant when other syndromic features may not be apparent allows for timely parental screening for reproductive counseling and anticipatory evaluation of cardiac and noncardiac features."
    explanation: States why testing should not wait for syndromic features to declare themselves.
- name: Whole-genome or whole-exome sequencing in deletion-negative cases
  description: >
    Sequencing has real yield in patients without the deletion. In a Japanese series of 11
    deletion-negative patients, five carried pathogenic TMEM260 variants and two more carried
    de novo variants in GATA6 and NOTCH1, so a majority of the cohort received a molecular
    diagnosis. The yield is population-dependent, since the TMEM260 signal rests on a local
    founder variant, which is itself an argument for sequencing rather than for targeted
    panels built elsewhere.
  diagnosis_term:
    preferred_term: whole genome sequencing
    term:
      id: NCIT:C101294
      label: Whole Genome Sequencing
  evidence:
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We performed whole-genome sequencing of 11 Japanese patients having TA without 22q11.2 deletion. Among five patients, we identified pathogenic variants in TMEM260"
    explanation: Demonstrates the diagnostic yield of sequencing in deletion-negative patients.
- name: Genetic counselling
  description: >
    Follows from the genetic result and is a distinct clinical action. Counselling differs
    sharply by mechanism: a de novo 22q11.2 deletion carries low recurrence risk but a fifty
    percent transmission risk for the affected child, whereas biallelic TMEM260 disease is
    autosomal recessive with a one in four sibling recurrence risk and identifiable carrier
    parents.
  diagnosis_term:
    preferred_term: genetic counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:32049433
    reference_title: "22q11.2 deletion syndrome and congenital heart disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "allows for timely parental screening for reproductive counseling and anticipatory evaluation of cardiac and noncardiac features"
    explanation: States the reproductive-counselling purpose that the genetic diagnosis serves.
treatments:
- name: Neonatal complete surgical repair
  description: >
    The definitive treatment and the only one that changes the outcome. The ventricular septal
    defect is closed so the trunk becomes the aorta and arises from the left ventricle alone,
    the pulmonary arteries are separated from the trunk, and continuity from the right
    ventricle to the pulmonary arteries is re-established with a conduit. It is performed in
    the neonatal period, before pulmonary vascular disease develops, and it carries an
    in-hospital mortality around one in ten in contemporary national data.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: cardiac surgery
    term:
      id: NCIT:C157806
      label: Cardiac Surgery
  target_mechanisms:
  - target: Unobstructed pulmonary blood flow at systemic pressure
    treatment_effect: INHIBITS
    description: >
      Separating the pulmonary arteries from the trunk and interposing a conduit removes the
      pulmonary bed's exposure to systemic pressure and unrestricted flow.
    evidence:
    - reference: PMID:32557823
      reference_title: "Outcomes of truncus arteriosus repair and predictors of mortality."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Overall, 3009 neonates met inclusion criteria; a total of 326 patients died during the hospitalization (10.8%)."
      explanation: Establishes neonatal repair as standard practice at national scale and quantifies its mortality.
  - target: Obligatory mixing of systemic and pulmonary venous return
    treatment_effect: INHIBITS
    description: >
      Closing the ventricular septal defect commits the trunk to the left ventricle and
      abolishes the obligatory admixture.
    evidence:
    - reference: PMID:38884754
      reference_title: "Molecular Pathways and Animal Models of Truncus Arteriosus."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "the outflow tract of the heart is divided into two distinct channels to separate the oxygenated systemic blood flow from the deoxygenated pulmonary circulation"
      explanation: States the separation of circulations that the operation restores surgically; PARTIAL because the source describes normal development rather than the operation.
  evidence:
  - reference: PMID:32557823
    reference_title: "Outcomes of truncus arteriosus repair and predictors of mortality."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "necrotizing enterocolitis (aOR = 3.10; 95% CI: 1.24-7.74; P = .015) and presence of venous thrombosis (aOR = 13.5; 95% CI: 6.7-27.2; P < .001)"
    explanation: Identifies comorbidities carrying the highest adjusted operative risk, which is what perioperative planning acts on.
- name: Serial right ventricle to pulmonary artery conduit replacement
  description: >
    A consequence of the repair rather than a treatment of the disease. The conduit does not
    grow, so it is outgrown and becomes obstructive, and it is replaced repeatedly through
    childhood and adolescence. This converts a neonatal emergency into a lifelong surgical
    relationship, and it is the main reason these patients need permanent congenital cardiology
    follow-up rather than discharge after successful repair.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: cardiac surgery
    term:
      id: NCIT:C157806
      label: Cardiac Surgery
  target_mechanisms:
  - target: Pulmonary vascular obstructive disease
    treatment_effect: INHIBITS
    description: >
      Maintaining an unobstructed conduit preserves the low-pressure separation of the
      pulmonary circulation that the original repair created.
- name: Preoperative anticongestive medical therapy
  description: >
    Diuresis and afterload reduction to control pulmonary overcirculation while the infant is
    prepared for surgery. It is a holding measure with a specific trap: supplemental oxygen
    lowers pulmonary vascular resistance and therefore increases pulmonary flow, so generous
    oxygen makes the physiology worse in an infant whose saturation looks reassuringly high.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: diuretic
      term:
        id: NCIT:C448
        label: Diuretic
  target_mechanisms:
  - target: Pulmonary overcirculation and volume-overload heart failure
    treatment_effect: MODULATES
    description: >
      Diuresis and afterload reduction relieve congestion without altering the anatomy that
      causes it.
- name: Extracorporeal membrane oxygenation
  description: >
    Rescue support, used in about seven percent of these admissions. Its association with a
    very high mortality odds ratio should be read as severity marking rather than harm: it is
    used in infants who are dying, and the confounding by indication is total.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: extracorporeal membrane oxygenation
    term:
      id: NCIT:C171507
      label: Extracorporeal Membrane Oxygenation
  target_mechanisms:
  - target: Perioperative myocardial ischaemia
    treatment_effect: BYPASSES
    description: >
      Extracorporeal support maintains systemic perfusion and oxygenation while the injured
      myocardium recovers.
    evidence:
    - reference: PMID:32557823
      reference_title: "Outcomes of truncus arteriosus repair and predictors of mortality."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Extracorporeal membrane oxygenation utilization was 7.1%."
      explanation: Quantifies how often extracorporeal support is used in this population.
  evidence:
  - reference: PMID:32557823
    reference_title: "Outcomes of truncus arteriosus repair and predictors of mortality."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients who received extracorporeal membrane oxygenation support or had cardiac catheterization procedure during the hospitalization had increased odds of mortality"
    explanation: Reports the mortality association; PARTIAL and directionally uninterpretable as a treatment effect, because the sickest infants are the ones cannulated.
genetic:
- name: TBX1
  gene_term:
    preferred_term: TBX1
    term:
      id: hgnc:11592
      label: TBX1
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  notes: >
    TBX1 sits within the 22q11.2 deleted region and haploinsufficiency for it is regarded as
    the principal driver of the conotruncal phenotype in the deletion syndrome. It is curated
    as causative in that dosage context rather than as a gene in which point mutations are
    the usual route to this malformation. The deletion is present in an estimated 12 to 35
    percent of truncus arteriosus cases and is the single largest identified cause.
  evidence:
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most common cause of TA is 22q11.2 deletion syndrome, accounting for 12-35% of all TA cases."
    explanation: Quantifies the deletion's contribution, which is the basis for treating this locus as the leading cause.
  - reference: PMID:38884753
    reference_title: "Human Genetics of Truncus Arteriosus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Integrated human genetics and molecular/developmental biology studies have revealed that truncus arteriosus is highly associated with 22q11.2 deletion syndrome."
    explanation: Independent statement of the association from a genetics review.
- name: TMEM260
  gene_term:
    preferred_term: TMEM260
    term:
      id: hgnc:20185
      label: TMEM260
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  notes: >
    Biallelic loss-of-function TMEM260 variants cause structural heart defects and renal
    anomalies syndrome, and account for a large share of deletion-negative truncus arteriosus
    in Japan. The mechanism is autosomal recessive, which matters for counselling because it
    gives a one in four sibling recurrence risk rather than the low recurrence of a de novo
    deletion. The Japanese signal rests on a single founder variant, c.1617del, estimated to
    have arisen about 23 000 years ago and carried at 0.36 percent allele frequency, so the
    gene's share of cases is expected to be population-specific rather than universal.
  evidence:
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Among five patients, we identified pathogenic variants in TMEM260; the biallelic loss-of-function variants of which have recently been associated with structural heart defects and renal anomalies syndrome (SHDRA)."
    explanation: Establishes biallelic TMEM260 loss of function as a cause in five of 11 deletion-negative patients.
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Based on the allele frequency of the c.1617del variant in the Japanese population (0.36%), approximately 26% of Japanese patients afflicted with TA could harbor homozygous c.1617del variants."
    explanation: Quantifies the founder variant's projected population-level contribution, and by construction its population specificity.
- name: NKX2-6
  gene_term:
    preferred_term: NKX2-6
    term:
      id: hgnc:32940
      label: NKX2-6
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  notes: >
    A homozygous F151L homeodomain variant was mapped by autozygosity in a large
    consanguineous family with common arterial trunk. The gene is expressed in pharyngeal
    endoderm and embryonic outflow tract myocardium, which fits. The instructive complication
    is that mice homozygous for a targeted Nkx2.6 mutation are normal, with Nkx2.5 expression
    expanding into the territory Nkx2.6 vacates, so the mouse null is rescued by functional
    complementation that apparently does not operate in the human. That makes this locus a
    worked example of why a normal knockout phenotype does not refute a human genetic finding.
  evidence:
  - reference: PMID:15649947
    reference_title: "Common arterial trunk associated with a homeodomain mutation of NKX2.6."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We have used autozygosity mapping of a large consanguineous family segregating CAT to map the causative locus to chromosome 8p21. An F151L mutation was identified in the homeodomain of NKX2.6"
    explanation: The mapping and variant identification in a segregating consanguineous family.
  - reference: PMID:15649947
    reference_title: "Common arterial trunk associated with a homeodomain mutation of NKX2.6."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Introduction of F157L into human NKX2.5 substantially reduced its transcription activating function, its synergism with partners at the atrial natriuretic factor (ANF) and connexin-40 (Cx40) promoters and its specific DNA binding."
    explanation: Functional evidence for the variant's effect, obtained in the NKX2.5 surrogate because NKX2.6 targets were unknown.
- name: GATA6
  gene_term:
    preferred_term: GATA6
    term:
      id: hgnc:4174
      label: GATA6
  relationship_type: CAUSATIVE
  variant_origin: DE_NOVO
  notes: >
    A de novo pathogenic GATA6 variant was identified in one deletion-negative patient in the
    Japanese whole-genome sequencing series, consistent with the wider role of GATA-family
    transcription factors in conotruncal development.
  evidence:
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In one patient, we identified a de novo pathogenic variant in GATA6"
    explanation: The single-patient de novo finding, curated at the strength the source supports.
- name: NOTCH1
  gene_term:
    preferred_term: NOTCH1
    term:
      id: hgnc:7881
      label: NOTCH1
  relationship_type: UNKNOWN
  variant_origin: DE_NOVO
  notes: >
    A de novo variant described by the authors as probably pathogenic was found in one
    deletion-negative patient. Curated with relationship_type UNKNOWN rather than causative
    because the source itself qualifies the classification, and a single probably-pathogenic
    de novo variant in a gene with a broad cardiac phenotype does not establish this
    malformation as its consequence.
  evidence:
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "in another patient, we identified a de novo probably pathogenic variant in NOTCH1"
    explanation: The authors' own hedged classification, which is the reason this gene is not curated as causative.
classifications:
  harrisons_chapter:
  - classification_value: CARDIOVASCULAR
    notes: >-
      A structural congenital cardiovascular malformation. The syndromic 22q11.2-deleted
      subgroup additionally carries immune, endocrine, and neurodevelopmental features that
      fall outside this chapter, but the entity curated here is the cardiac lesion.
inheritance:
- name: Autosomal dominant, 22q11.2 deletion
  description: >
    The 22q11.2 deletion is usually de novo but is transmitted as an autosomal dominant trait
    once present, so an affected individual has a fifty percent transmission risk. This is the
    mode that applies to the largest identified genetic subgroup, and it is why deletion
    testing changes reproductive counselling for the patient as well as for the parents.
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  evidence:
  - reference: PMID:32049433
    reference_title: "22q11.2 deletion syndrome and congenital heart disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Early identification of a 22q11.2 deletion in the neonate or infant when other syndromic features may not be apparent allows for timely parental screening for reproductive counseling and anticipatory evaluation of cardiac and noncardiac features."
    explanation: States the reproductive-counselling consequence that follows from the dominant transmission of the deletion.
- name: Autosomal recessive, biallelic TMEM260 or NKX2-6
  description: >
    Biallelic loss-of-function variants in TMEM260 and biallelic homeodomain-disrupting
    variants in NKX2-6 both cause this malformation recessively. The counselling implication is
    opposite to the deletion case: a one in four sibling recurrence risk with carrier parents,
    rather than a low recurrence risk with a fifty percent transmission risk. Both were found
    in consanguineous or founder settings, which is where recessive causes surface first.
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the biallelic loss-of-function variants of which have recently been associated with structural heart defects and renal anomalies syndrome (SHDRA)"
    explanation: Establishes biallelic, and therefore recessive, inheritance for the TMEM260 route.
  - reference: PMID:32198970
    reference_title: "NKX2-6 related congenital heart disease: Biallelic homeodomain-disrupting variants and truncus arteriosus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Two consanguineous families with TA were previously identified to have homozygous nonsense variants within the gene NKX2-6."
    explanation: Establishes homozygous, and therefore recessive, inheritance for the NKX2-6 route, in the consanguineous setting where it was found.
environmental:
- name: Maternal pregestational diabetes
  description: >
    The best-established non-genetic risk factor, and the only modifiable one. The National
    Birth Defects Prevention Study puts the adjusted odds ratio for this malformation at 14.9
    (95% CI 7.6 to 29.3), one of a handful of defects in that study exceeding a ten-fold
    increased risk. Unlike the genetic causes, this one is preventable in principle, which is
    why it carries prevention weight out of proportion to the fraction of cases it explains. No
    mechanism is asserted here: the source states the teratogenic mechanism is unknown.
  influences_mechanisms:
  - target: Cardiac neural crest and second heart field program disruption
    environmental_effect: PREDISPOSES
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >
      Maternal hyperglycaemia during the fifth to eighth week of gestation is proposed to
      perturb the neural crest and second heart field program during outflow tract septation.
    evidence:
    - reference: PMID:31454511
      reference_title: "Specific birth defects in pregnancies of women with diabetes: National Birth Defects Prevention Study, 1997-2011."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "the teratogenic mechanism behind the increase risk for birth defects is still unknown"
      explanation: PARTIAL, and deliberately so. This edge asserts that the exposure acts on the neural crest and second heart field program, and the source states plainly that the teratogenic mechanism is unknown. The association is strong and disease-specific; the step from association to this particular developmental mechanism is not evidenced, and the snippet records that rather than papering over it.
  evidence:
  - reference: PMID:31454511
    reference_title: "Specific birth defects in pregnancies of women with diabetes: National Birth Defects Prevention Study, 1997-2011."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "truncus arteriosus (adjusted odds ratio, 14.9; 95% confidence interval, 7.6-29.3)"
    explanation: The disease-specific adjusted effect estimate from the National Birth Defects Prevention Study, and the strongest available evidence for this exposure. A roughly fifteen-fold adjusted odds ratio with a confidence interval well clear of one places this malformation among the defects most strongly associated with pregestational diabetes.
  - reference: PMID:31454511
    reference_title: "Specific birth defects in pregnancies of women with diabetes: National Birth Defects Prevention Study, 1997-2011."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "For some defect categories, and particularly for pregestational diabetes, there were few exposed cases, leading to imprecise estimates."
    explanation: The authors' own precision caveat, which is why the confidence interval on the truncus arteriosus estimate is as wide as it is; PARTIAL because it qualifies the estimate rather than supporting the association.
  notes: >
    No ECTO term is bound. Maternal pregestational diabetes is a maternal disease state rather
    than an exposure to an agent, and the ECTO exposure hierarchy has no term that expresses it
    without asserting a specific chemical exposure the sources do not support.

    A retinoic-acid mechanism is often proposed for diabetic embryopathy, namely
    hyperglycaemia-induced disturbance of embryonic retinoic acid catabolism sensitising the
    conotruncal field. It was in an earlier draft of this description and has been removed. The
    deep-research report sources it only to PMC identifiers that were never fetched or verified,
    and the one study cited here states outright that the teratogenic mechanism is unknown.
    Recording it as a lead in notes is honest; asserting it in a description backed by a source
    that disclaims it is not.
experimental_models:
- name: Splotch mutant mouse
  description: >
    The founding genetic model, and the experiment that established the cardiac neural crest as
    the tissue of origin for this malformation. Homozygous Sp1H mutants fail to septate the
    truncus arteriosus and develop persistent truncus arteriosus with an ostium opening to the
    right ventricle, together with aortic arch variants and thymic, parathyroid, and
    ultimobranchial body defects. That pattern is the point: the same mutation affects every
    structure the neural crest populates, which is the argument that the cardiac lesion is a
    neurocristopathy rather than a local septation failure. The model dies mid-gestation, so it
    cannot address postnatal physiology at all.
  experimental_model_type: OTHER
  organism:
    preferred_term: house mouse
    term:
      id: NCBITaxon:10090
      label: Mus musculus
  modeled_mechanisms:
  - target: Cardiac neural crest and second heart field program disruption
    description: >
      Splotch disrupts neural-crest-derived cell populations, which is the trigger node here.
  - target: Failure of aorticopulmonary septation
    description: >
      The mutant reproduces the septation failure itself.
  publication: PMID:2619088
  evidence:
  - reference: PMID:2619088
    reference_title: "Persistent truncus arteriosus in the Splotch mutant mouse."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "It is shown that in homozygous mutant embryos, the septation of the truncus arteriosus does not proceed normally, resulting in persistent truncus arteriosus."
    explanation: Direct recapitulation of the human malformation from a neural crest defect.
  - reference: PMID:2619088
    reference_title: "Persistent truncus arteriosus in the Splotch mutant mouse."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "These results provide indirect evidence, that cells contributing to the aortic arches and the septum of the truncus arteriosus in mice are derived from the neural crest."
    explanation: The inference that makes this model mechanistically informative rather than merely phenocopying, and the basis for the trigger node in this entry.
  - reference: PMID:2619088
    reference_title: "Persistent truncus arteriosus in the Splotch mutant mouse."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The development of the thymus, the parathyroid and the ultimobranchial bodies are also variably affected in mutants."
    explanation: The extracardiac involvement that parallels the 22q11.2 phenotype in humans and supports a shared pharyngeal and neural-crest origin.
- name: Tbx1 conditional null mouse with beta-catenin dosage rescue
  description: >
    The canonical model for the 22q11.2 route, and the one that identifies the molecular error.
    Inactivating Tbx1 in anterior heart field mesoderm produces premature expression of
    pro-differentiation genes and a persistent truncus arteriosus, so the defect is one of
    developmental timing rather than of cell absence. Removing one allele of beta-catenin
    rescues the outflow tract defect in 61 percent of double mutants, which establishes an
    antagonistic relationship between the two pathways and shows the malformation is
    developmentally reversible in principle. That is the closest thing to a mechanistic target
    this disease has.
  experimental_model_type: OTHER
  organism:
    preferred_term: house mouse
    term:
      id: NCBITaxon:10090
      label: Mus musculus
  modeled_mechanisms:
  - target: Cardiac neural crest and second heart field program disruption
    description: >
      Tbx1 inactivation in anterior heart field mesoderm models the second heart field arm of
      the trigger node, complementing the neural crest arm modelled by Splotch.
  - target: Failure of aorticopulmonary septation
    description: >
      The mutant reproduces the failure of septation between aorta and pulmonary trunk.
  publication: PMID:28346476
  evidence:
  - reference: PMID:28346476
    reference_title: "Reduced dosage of β-catenin provides significant rescue of cardiac outflow tract anomalies in a Tbx1 conditional null mouse model of 22q11.2 deletion syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Inactivation of Tbx1 in the anterior heart field (AHF) mesoderm in the mouse results in premature expression of pro-differentiation genes and a persistent truncus arteriosus (PTA) in which septation does not form between the aorta and pulmonary trunk."
    explanation: States both the phenotype and the molecular error behind it, premature differentiation rather than loss of the progenitor population.
  - reference: PMID:28346476
    reference_title: "Reduced dosage of β-catenin provides significant rescue of cardiac outflow tract anomalies in a Tbx1 conditional null mouse model of 22q11.2 deletion syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "When both alleles of Tbx1 and one allele of β-catenin were inactivated in the Mef2c-AHF-Cre domain, 61% of them (n = 34) showed partial or complete rescue of the PTA defect."
    explanation: The genetic rescue, which is the strongest evidence that this is a dosage-sensitive signalling imbalance rather than an irrecoverable structural loss.
prevalence:
- population: Critical congenital heart disease
  measure_type: POINT_PREVALENCE
  prevalence_class: RARE
  notes: >
    Truncus arteriosus accounts for about 4 percent of all critical congenital heart disease,
    the subset requiring intervention in the newborn period. This is a share of a diagnostic
    category rather than a population rate, and is recorded as such.
  evidence:
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "TA accounts for 4% of all critical congenital heart diseases."
    explanation: The share of critical congenital heart disease attributable to this lesion.
- population: 22q11.2 deletion syndrome, livebirths
  measure_type: BIRTH_PREVALENCE
  prevalence_class: BAND_1_5_PER_10000
  rate_per_100000: 20.0
  notes: >
    The deletion syndrome that causes 12 to 35 percent of truncus arteriosus has an estimated
    prevalence of 1 in 4000 to 6000 livebirths, with 60 to 80 percent of those having a
    cardiac malformation. Recorded here as denominator context for the leading genetic cause,
    not as the prevalence of this malformation.
  evidence:
  - reference: PMID:32049433
    reference_title: "22q11.2 deletion syndrome and congenital heart disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The 22q11.2 deletion syndrome has an estimated prevalence of 1 in 4-6,000 livebirths."
    explanation: Birth prevalence of the deletion syndrome.
  - reference: PMID:32049433
    reference_title: "22q11.2 deletion syndrome and congenital heart disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Approximately 60-80% of patients have a cardiac malformation most commonly including a subset of conotruncal defects"
    explanation: The cardiac penetrance of the deletion, which converts its birth prevalence into a conotruncal-disease denominator.
differential_diagnoses:
- name: Tetralogy of Fallot with pulmonary atresia
  description: >
    The closest anatomic mimic, and separating them is consequential rather than academic.
    Both can present as a ventricular septal defect with a single visible outflow vessel. The
    distinction is whether pulmonary arteries arise from that vessel, as they do in truncus,
    or are supplied through a duct or aortopulmonary collaterals, as in pulmonary atresia.
    Physiology follows anatomy in opposite directions: truncus floods the lungs and needs
    pulmonary flow restricted, whereas pulmonary atresia starves them and needs the duct kept
    open with prostaglandin.
  evidence:
  - reference: PMID:32049433
    reference_title: "22q11.2 deletion syndrome and congenital heart disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a subset of conotruncal defects (tetralogy of Fallot, truncus arteriosus, interrupted aortic arch type B)"
    explanation: Places the two lesions in the same conotruncal family sharing a genetic cause; PARTIAL because the source does not address their differentiation.
- name: Aortopulmonary window
  description: >
    Also produces a communication between aorta and pulmonary artery with pulmonary
    overcirculation, but the semilunar valves are two and separate, and the ventricular septum
    is usually intact. The count of semilunar valves is the discriminating observation on
    echocardiography.
  evidence:
  - reference: PMID:15649947
    reference_title: "Common arterial trunk associated with a homeodomain mutation of NKX2.6."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A common arterial trunk (CAT) is often diagnosed as PTA in the absence of evidence of embryological mechanism."
    explanation: Notes explicitly that the diagnostic label is applied on appearance without embryologic confirmation, which is the reasoning gap this differential exploits; PARTIAL because aortopulmonary window is not named.
- name: Structural heart defects and renal anomalies syndrome
  description: >
    Not a competing cardiac diagnosis but a syndromic context that changes what else to look
    for. Biallelic TMEM260 loss of function produces this syndrome, so an infant with truncus
    arteriosus and no 22q11.2 deletion warrants renal imaging, and the recurrence counselling
    is recessive rather than de novo.
  evidence:
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the biallelic loss-of-function variants of which have recently been associated with structural heart defects and renal anomalies syndrome (SHDRA)"
    explanation: Links the genetic finding to the extracardiac syndrome that should then be evaluated.
clinical_burden:
  burden_level: HIGH
  rationale: >
    A critical congenital heart lesion that is uniformly fatal in infancy without surgery, and
    whose surgical treatment still carries about 10.8 percent in-hospital mortality in
    contemporary national data. Repair is not curative: the right ventricle to pulmonary
    artery conduit is outgrown and must be replaced serially through childhood, and truncal
    valve regurgitation drives further reoperation, so survivors carry a lifelong surgical and
    surveillance burden.
  notes: >
    A substantial minority carry a 22q11.2 deletion, which adds hypocalcaemia,
    immunodeficiency, palatal and feeding disorders, and neurodevelopmental and psychiatric
    morbidity to the cardiac disease. Those patients have more perioperative complications than
    non-syndromic patients but do not, in the reported data, have higher surgical mortality,
    so the syndromic burden is chiefly a matter of complication management and lifelong
    non-cardiac care rather than of operative survival.
  evidence:
  - reference: PMID:32557823
    reference_title: "Outcomes of truncus arteriosus repair and predictors of mortality."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Overall, 3009 neonates met inclusion criteria; a total of 326 patients died during the hospitalization (10.8%)."
    explanation: Contemporary in-hospital mortality in a national neonatal cohort.
  - reference: PMID:32049433
    reference_title: "22q11.2 deletion syndrome and congenital heart disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cardiac patients with a 22q11.2 deletion do not generally experience higher mortality upon surgical intervention but suffer more peri-operative complications than their non-syndromic counterparts."
    explanation: Separates the syndromic complication burden from operative mortality, which is the distinction the notes above rest on.
discussions:
- discussion_id: deletion_positive_survival_paradox
  prompt: >
    Why do infants with truncus arteriosus and a 22q11.2 deletion appear to have an inverse
    risk of in-hospital death despite carrying more comorbidity?
  kind: CONTROVERSY
  status: OPEN
  attaches_to:
  - pathophysiology#Cardiac neural crest and second heart field program disruption
  - pathophysiology#Perioperative myocardial ischaemia
  rationale: >
    The national inpatient analysis found 22q11.2 deletion associated with an inverse risk of
    death despite more non-cardiac comorbidity, and a separate review reports that deletion
    patients have more perioperative complications without higher surgical mortality. Taken
    at face value the finding is paradoxical. Several explanations compete and imply different
    things. Deletion-positive infants are identified earlier and enter tertiary care sooner,
    so the association may be a surrogate for timely referral rather than a biological
    protection. Their anatomy may differ systematically, and there is a hint of this in an
    older series where deletion-positive patients were enriched for types with pulmonary
    stenosis, which would restrict pulmonary flow and postpone decompensation. Or the finding
    may be an artefact of administrative coding, since a deletion diagnosis has to be recorded
    to be counted and is more likely to be recorded in survivors who reach genetic testing.
    The last of these would make the result an artefact of exactly the data source that
    produced it.
  proposed_experiments:
  - experiment_id: exp_pta_deletion_status_outcome_registry
    name: Prospective registry comparison of outcomes by 22q11.2 status with anatomic and referral covariates
    description: >-
      In a multicentre congenital cardiac surgical registry with universal deletion testing at
      diagnosis, compare operative and one-year mortality by deletion status, adjusting for Van
      Praagh anatomic subtype, presence of pulmonary or truncal valve stenosis, coronary
      anomaly, age at referral, and preoperative clinical state.
    decision_criterion: >-
      A persisting survival advantage after adjustment for anatomy and referral timing would
      point to a genuine biological or care-pathway effect worth explaining; loss of the
      association on adjustment would establish it as confounding and would retire the
      paradox.
  evidence:
  - reference: PMID:32557823
    reference_title: "Outcomes of truncus arteriosus repair and predictors of mortality."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "22q11.2 deletion syndrome was associated with an inverse risk of death despite having more noncardiac comorbidities"
    explanation: The observation that creates the controversy.
  - reference: PMID:9316541
    reference_title: "Truncus arteriosus communis associated with chromosome 22q11 deletion."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In truncus arteriosus communis, the rare type A3 with major aortopulmonary collateral arteries and pulmonary ostial stenosis and type A1 with pulmonary artery stenosis are associated with del 22q11."
    explanation: Supports the anatomic-difference explanation, since the deletion-associated subtypes carry pulmonary flow restriction; PARTIAL because the series of 15 patients is small and outcomes are not reported.
- discussion_id: nkx2_6_mouse_human_discrepancy
  prompt: >
    Why does a targeted Nkx2.6 mutation leave mice normal when a homozygous NKX2.6 homeodomain
    variant causes common arterial trunk in humans?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Cardiac neural crest and second heart field program disruption
  - pathophysiology#Failure of aorticopulmonary septation
  rationale: >
    The human evidence is strong: autozygosity mapping in a large consanguineous family
    localised the lesion to 8p21, the variant sits in the homeodomain, and the corresponding
    substitution in the NKX2.5 surrogate substantially reduced transcriptional activation, DNA
    binding, and synergy at target promoters. Yet Nkx2.6 null mice are normal, and the reason
    appears to be that Nkx2.5 expression expands into the territory Nkx2.6 vacates. If that
    complementation is mouse-specific, then the mouse null is simply the wrong assay for this
    gene and its normality carries no evidential weight against the human finding. If instead
    complementation also operates in humans, then a simple loss-of-function model cannot be
    right and the F151L variant is doing something a null does not, most plausibly acting as a
    dominant negative on shared NKX partners. The two readings imply different variant
    interpretation rules for this gene in a clinical laboratory, which is why this is not
    merely a modelling curiosity. The human side of the discrepancy has since strengthened:
    further individuals with biallelic homeodomain-disrupting NKX2-6 variants have been
    reported, so the association no longer rests on the single original kindred while the
    mouse null remains normal.
  proposed_experiments:
  - experiment_id: exp_nkx26_knockin_versus_null
    name: Comparison of an Nkx2.6 F151L knock-in against an Nkx2.6 null on matched backgrounds
    description: >-
      Generate a knock-in mouse carrying the orthologous homeodomain substitution alongside a
      true null on the same background, assess outflow tract septation in both, and map Nkx2.5
      expression domains in each to determine whether the compensatory expansion occurs in the
      knock-in as it does in the null.
    decision_criterion: >-
      A septation defect in the knock-in but not the null would establish a dominant-negative
      rather than loss-of-function mechanism and would mean null alleles should not be equated
      with this missense variant; normality of both, with equivalent Nkx2.5 expansion, would
      confirm that mouse complementation makes the model uninformative for this human gene.
  evidence:
  - reference: PMID:15649947
    reference_title: "Common arterial trunk associated with a homeodomain mutation of NKX2.6."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "mice homozygous for a targeted mutation of Nkx2.6 are normal. However, in these mice, it has been shown that Nkx2.5 expression expands into regions lacking Nkx2.6, suggesting functional complementation."
    explanation: States the mismatch and the compensation hypothesis proposed to explain it, in the same paper that reports the human variant.
  - reference: PMID:32198970
    reference_title: "NKX2-6 related congenital heart disease: Biallelic homeodomain-disrupting variants and truncus arteriosus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Two consanguineous families with TA were previously identified to have homozygous nonsense variants within the gene NKX2-6."
    explanation: Independent replication of the human association, which is what makes the normal mouse null a genuine discrepancy rather than a reason to doubt the original report.
  - reference: PMID:32198970
    reference_title: "NKX2-6 related congenital heart disease: Biallelic homeodomain-disrupting variants and truncus arteriosus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "NKX2-6 is a known downstream target of TBX1, an important transcriptional regulator implicated in the cardiac phenotype of 22q11.2 microdeletion syndrome."
    explanation: Places NKX2-6 downstream of TBX1, which unifies the recessive NKX2-6 route and the dominant 22q11.2 route into one pathway and is why both are curated against the same trigger node.
- discussion_id: population_specific_genetic_architecture
  prompt: >
    Is the genetic architecture of deletion-negative truncus arteriosus population-specific, and
    what does that mean for genetic testing offered outside the populations it was described in?
  kind: OPEN_QUESTION
  status: OPEN
  attaches_to:
  - pathophysiology#Cardiac neural crest and second heart field program disruption
  rationale: >
    TMEM260 emerged as a major cause of deletion-negative truncus arteriosus in Japan, but the
    signal rests on a founder variant carried at 0.36 percent allele frequency in that
    population and estimated to be about 23 000 years old. A founder allele's contribution is
    by construction a property of the population, not of the gene, so the projection that about
    a quarter of Japanese cases are homozygous for it says nothing about how often TMEM260
    explains cases elsewhere. Two practical consequences follow and neither is settled. A
    targeted panel built on the Japanese finding may have low yield in other populations, while
    a broad sequencing approach would find whatever the local architecture is. And the absence
    of comparable studies elsewhere means the field currently cannot distinguish "TMEM260 is a
    Japanese founder effect" from "TMEM260 is a general cause that was first found in Japan."
  proposed_experiments:
  - experiment_id: exp_pta_multiancestry_sequencing
    name: Multi-ancestry whole-genome sequencing of deletion-negative truncus arteriosus
    description: >-
      Sequence deletion-negative truncus arteriosus cohorts recruited across several ancestries,
      report diagnostic yield by gene and by ancestry, and test specifically whether biallelic
      TMEM260 loss of function contributes outside East Asian populations and at what frequency.
    decision_criterion: >-
      A comparable TMEM260 contribution across ancestries would establish it as a general cause
      and justify including it on universal panels; a contribution confined to populations
      carrying the founder allele would establish the architecture as population-specific and
      would argue for genome-wide sequencing rather than transplanted panels.
  evidence:
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This study highlights TMEM260, especially c.1617del, as a major genetic cause of TA in the Japanese population."
    explanation: The authors localise their own claim to the Japanese population, which is the premise of this question.
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "However, no major causes of TA other than 22q11.2 deletion have been reported."
    explanation: States the prior state of knowledge that a single-population study has now changed, and by implication how thin the comparative evidence is.
- discussion_id: majority_of_cases_genetically_unexplained
  prompt: >
    What accounts for the majority of truncus arteriosus cases that carry neither a 22q11.2
    deletion nor an identified monogenic cause?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Cardiac neural crest and second heart field program disruption
  - pathophysiology#Failure of aorticopulmonary septation
  rationale: >
    The deletion explains 12 to 35 percent of cases. Sequencing in deletion-negative patients
    has now identified TMEM260, GATA6, and NOTCH1 variants, but in a single small
    population-specific cohort. Across the whole disease, most cases still have no molecular
    diagnosis. Three candidate explanations are open. There may be further monogenic causes
    that adequately powered multi-ancestry sequencing will find, which the recent TMEM260
    result makes plausible. Causation may be substantially oligogenic or multifactorial, with
    the developmental program failing on a combination of variants none of which is
    individually diagnostic. Or non-genetic causes may account for a real share, with maternal
    pregestational diabetes and retinoic-acid-pathway exposures the leading candidates and
    plausibly interacting with genotype. These are not exclusive, and distinguishing their
    relative contributions determines whether the right investment is deeper sequencing or
    exposure epidemiology.
  proposed_experiments:
  - experiment_id: exp_pta_trio_sequencing_with_exposure_data
    name: Trio sequencing of unexplained truncus arteriosus with linked maternal exposure data
    description: >-
      Sequence parent-child trios for cases negative for 22q11.2 deletion and known monogenic
      causes, quantify the de novo variant burden in outflow-tract developmental genes against
      matched controls, and link each case to prospectively recorded maternal pregestational
      diabetes status and periconceptional retinoid exposure.
    decision_criterion: >-
      Significant de novo burden in outflow-tract developmental pathways would support further
      monogenic causes and justify deeper sequencing; a null burden with strong exposure
      association would redirect effort to exposure epidemiology and prevention.
  evidence:
  - reference: PMID:38351237
    reference_title: "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most common cause of TA is 22q11.2 deletion syndrome, accounting for 12-35% of all TA cases. However, no major causes of TA other than 22q11.2 deletion have been reported."
    explanation: Quantifies the explained fraction and states that the remainder was unaccounted for before this study.
  - reference: PMID:38884753
    reference_title: "Human Genetics of Truncus Arteriosus."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other congenital malformation syndromes and variants in genes encoding TBX, GATA, and NKX transcription factors and some signaling proteins have also been reported as its etiology."
    explanation: Documents the scattered additional genetic causes reported to date; PARTIAL because it does not quantify what share of cases they explain.
notes: >
  Terminology. Curated as persistent truncus arteriosus, MONDO:0018072, which is the same
  entity as common arterial trunk. One source notes that a common arterial trunk is often
  labelled persistent truncus arteriosus without embryologic confirmation, so the two names
  are treated as synonyms of a single curated entity here rather than as separable entities.

  Anatomic subtypes. The Collett and Edwards and Van Praagh classifications are referenced in
  descriptions but are not curated as has_subtypes entries, because the mechanism curated here
  is shared across all of them and the subtypes differ in the origin pattern of the pulmonary
  arteries rather than in pathogenesis. Van Praagh type A4, with interrupted aortic arch, is
  captured through the interrupted aortic arch phenotype instead.

  Module conformance. One node conforms to pulmonary_vascular_remodeling. The fit is at the
  obstructive-remodelling node only: the upstream trigger here is unrestricted high-pressure
  high-flow exposure of a normal pulmonary bed rather than the endothelial and BMPR2 lesion
  the module's earlier nodes model, so conformance is deliberately declared at the single node
  where the mechanisms genuinely converge.

  Truncal valve ontology. Truncal valve regurgitation is curated against HP:0001659 Aortic
  regurgitation, because HPO has no truncal valve term and the truncal valve is the common
  semilunar valve from which the aortic valve would otherwise have formed. The preferred_term
  states the specific claim. This is a deliberate looser binding, not an oversight.

  Phenotypes not curated. Truncal valve stenosis and coarctation of the aorta are real
  features of this lesion, but no cached reference states either in a quotable sentence, and
  unlike right aortic arch there is not even a case-series observation to cite. They are named
  here so the gap is recorded rather than invisible. The frequencies quoted in the
  deep-research narrative (roughly 25 percent and 10 percent) are not used, since their sources
  were not fetched.

  Deliberately unevidenced descriptions. Several nodes, phenotypes, treatments, and
  progression phases carry a description with no evidence block: the single-trunk physiology
  consequences (cyanosis, overcirculation, pulmonary vascular obstructive disease), the
  clinical presentation (tachypnoea, failure to thrive, congestive heart failure), conduit
  reintervention, and preoperative anticongestive therapy. These are well-established, but the
  cached references for this entry do not contain a sentence that states them. Following the
  evidence SOP, the description is kept and the evidence block omitted rather than attaching a
  methods or objective sentence that would verify as an exact quote while supporting a
  different claim. This lowers the compliance score, which is the correct trade.

  Deep-research provenance. Curated from a claude_code deep-research report
  (research/Persistent_Truncus_Arteriosus-deep-research-claude_code.md) treated as leads only.
  The NEC preflight returned SKIP because MONDO records no causal gene for MONDO:0018072;
  manual checks confirmed the entity, with the report's gene profile (TMEM260, NKX2-6, TBX1,
  NKX2-5) and its OMIM 217095 consistent with the intended disease. Five identifiers suggested
  by the provider were verified against OAK and found to point at unrelated concepts
  (HP:0001719 is Double outlet right ventricle, not Truncus arteriosus, which is HP:0001660;
  CL:0002350 is endocardial cell, not cardiac neural crest cell; UBERON:0004151 is cardiac
  chamber, not outflow tract; hgnc:2673 is DAP3, not NKX2-6; hgnc:26160 is THNSL1, not
  TMEM260). All were corrected before curation. The report itself correctly warned against
  curating OMIM 226000, endocardial fibroelastosis, against this entity.

📚

References & Deep Research

Deep Research

1

Claude Code ▸

Persistent Truncus Arteriosus (PTA) — Comprehensive Disease Characteristics Research Report

claude-haiku-4-5-20251001, claude-sonnet-5 37 citations 2026-08-09T21:46:04.316155

Persistent Truncus Arteriosus (PTA) — Comprehensive Disease Characteristics Research Report

1. Disease Information

Overview: Persistent truncus arteriosus (PTA), also called truncus arteriosus communis or common arterial trunk, is a rare, cyanotic conotruncal congenital heart defect present at birth in which the embryonic truncus arteriosus fails to septate into a separate aorta and pulmonary trunk. As a result, a single arterial trunk arising from the heart via a single (truncal) semilunar valve overrides a ventricular septal defect (VSD) and gives origin to the coronary arteries, one or more pulmonary arteries, and the systemic circulation, producing obligatory mixing of oxygenated and deoxygenated blood (Wikipedia; NORD; StatPearls, PMID not applicable — review source).

Key identifiers: - OMIM: 217095 (Conotruncal Heart Malformations, CTHM) — PTA is nosologically grouped under this entry along with tetralogy of Fallot, DORV, and interrupted aortic arch, reflecting a shared developmental field defect (https://omim.org/entry/217095) - Orphanet: ORPHA:3384 (Common arterial trunk) (https://www.orpha.net/en/disease/detail/3384) - MONDO: MONDO:0018072 - ICD-10-CM: Q20.0 (Common arterial trunk) - MeSH: Truncus Arteriosus, Persistent - Related DiGeorge/22q11.2 deletion syndrome OMIM: 188400

Synonyms: Truncus arteriosus communis; common arterial trunk (CAT); persistent truncus arteriosus; truncus arteriosus (colloquial). Historically classified using the Collett and Edwards system (Types I–IV, based on pulmonary artery origin from the truncal root) and the Van Praagh system (Types A1–A4, which additionally incorporates VSD and aortic arch anomalies) — per StatPearls (NBK534774), Type A1/Type I (main pulmonary trunk arising from the left posterolateral truncal root, with a partially formed aorticopulmonary septum) is the most common, representing roughly half of cases; Type A2 (~21%) has separate, adjacent origins of the branch pulmonary arteries with an absent septum.

Evidence basis: Information is derived primarily from aggregated disease-level resources — clinical case series, single- and multi-center surgical outcome cohorts, autopsy/pathology series, and population-based birth-defect/epidemiological registries — rather than from a single large individual-patient EHR resource, reflecting the rarity of the condition.

2. Etiology

Disease Causal Factors

PTA arises from failure of aorticopulmonary (conotruncal) septation during cardiac outflow tract (OFT) morphogenesis — i.e., failure of the conotruncal ridges/aorticopulmonary septum to form and divide the common trunk into aorta and pulmonary trunk (StatPearls NBK534774; ScienceDirect topic overview). It is fundamentally a defect of the cardiac neural crest (CNC)–second heart field developmental unit, with contributing genetic (chromosomal, monogenic) and environmental/teratogenic causes (see Mechanism section for the causal chain).

Genetic Risk Factors

22q11.2 deletion syndrome (DiGeorge/velocardiofacial syndrome, OMIM 188400) is the single most important genetic association, identified in ~12–35% of PTA cases across series, with several series citing ~25% (StatPearls; PMID:9316541 "Truncus arteriosus communis associated with chromosome 22q11 deletion"). Congenital heart disease occurs in ~76% of 22q11.2-deletion patients overall, and conotruncal anomalies (TOF, interrupted aortic arch, PTA) predominate. TBX1 haploinsufficiency within the deleted region is considered the major driver of the cardiac outflow phenotype.
TMEM260 — Recently identified (2024) as a major non-22q11.2 genetic cause, particularly in East Asian (Japanese/Korean) populations. Biallelic loss-of-function TMEM260 variants (notably a founder variant, c.1617del, allele frequency ~0.36% in Japan) cause Structural Heart Defects and Renal Anomalies syndrome (SHDRA), and TMEM260 variants may account for over half of Japanese TA cases lacking a 22q11.2 deletion (PMID:38351237, "Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population"; correction PMID:38548934; companion paper PMC11043032).
NKX2-6 (OMIM *611770) — Homozygous/biallelic homeodomain-disrupting variants (e.g., F151L) identified via autozygosity mapping in consanguineous families with common arterial trunk (PMID:15649947, Heathcote et al., Hum Mol Genet 2005; also PMID:32198970/Ritter et al. 2020, biallelic NKX2-6 variants and truncus arteriosus).
NKX2-5 (OMIM 600584) — Variants reported in patients with PTA and interrupted aortic arch, reflecting a broader NKX2-5-associated conotruncal spectrum.
FOXC1/FOXC2 — Conditional inactivation in neural-crest cells produces cardiac outflow abnormalities in mouse models, implicating this pathway in human conotruncal disease.
GATA6 and other GATA-family transcription factors — implicated in conotruncal malformation spectrum.
A comprehensive 2024 review, "Human Genetics of Truncus Arteriosus" (PMID:38884753), summarizes that beyond 22q11.2, "other congenital malformation syndromes and variants in genes encoding TBX, GATA, and NKX transcription factors and some signaling proteins have also been reported as its etiology."
Suggested HGNC/gene identifiers: TBX1 (HGNC:11592), NKX2-6 (HGNC:2673), NKX2-5 (HGNC:2488), TMEM260 (HGNC:26160), FOXC1 (HGNC:3800), FOXC2 (HGNC:3801), GATA6 (HGNC:4174).

Environmental Risk Factors

Maternal pregestational diabetes mellitus: fetuses of diabetic pregnancies show a >3-fold increased risk of transposition of the great arteries, truncus arteriosus, and tricuspid atresia relative to non-diabetic pregnancies (PMC10671602, "Maternal Pre-Existing Diabetes: A Non-Inherited Risk Factor for Congenital Cardiopathies"). Diabetic embryopathy models show altered retinoic acid catabolism and dysregulated expression of cardiovascular developmental genes (PMC10449132).
Retinoic acid / isotretinoin exposure: retinoic-acid pathway dysregulation is a recognized teratogenic route to conotruncal and aortic arch anomalies; isotretinoin (a synthetic retinoic acid analog) carries an elevated CHD risk via this mechanism.
Gene-environment interaction: Maternal diabetic embryos show a synergistic increase in retinoic-acid-induced malformation susceptibility relative to euglycemic embryos, suggesting a "second hit" model relevant to human diabetic pregnancies (PMID:12196475 context, caudal regression/RA-diabetes interaction).
No consistent sex or racial predilection is reported (StatPearls); some series note a slight male predominance without statistical significance.

Protective Factors

No specific genetic or environmental protective factors for PTA are well-documented in the literature reviewed; periconceptional folic acid supplementation is broadly protective against congenital heart defects generally but is not specifically quantified for PTA in the sources reviewed.

Gene-Environment Interactions

The clearest documented interaction is the maternal diabetes × retinoic acid signaling axis: hyperglycemia alters embryonic retinoic acid catabolism, sensitizing the conotruncal developmental field to teratogen-induced (and likely intrinsic) septation failure (PMC10449132).

3. Phenotypes

Cardiac structural phenotype (congenital/present at birth; category: physical malformation)

Single arterial trunk with a single semilunar (truncal) valve overriding a large, typically non-restrictive VSD (StatPearls). — Suggested term: HP:0001719 Truncus arteriosus (note: cross-check exact HPO CURIE against the local OAK cache before committing; some search indices returned inconsistent HP codes for this exact term and it should be verified with runoak).
Truncal valve abnormality: valve may be bicuspid, tricuspid, quadricuspid, or (rarely) pentacuspid; quadricuspid morphology is itself a risk factor for later reoperation.
Truncal valve regurgitation — present in ~50% of patients, ranging mild to severe; a major driver of ventricular volume overload and heart failure (Martínez-Quintana, Transl Pediatr; StatPearls).
Truncal valve stenosis — less common (~25%), but poorly tolerated because it raises afterload on both ventricles simultaneously.
Right-sided or interrupted aortic arch — right aortic arch in ~21–36% of series; aortic arch interruption defines Van Praagh Type A4.
Coarctation of the aorta — critical coarctation reported in ~10% of cases.
Coronary artery anomalies of origin — reported in 37–80% of cases depending on series (ostial anomalies most common ~37–49%); no single consistent pattern, though the left coronary tends to arise more posteriorly than normal and the right coronary tends to arise from the anterior-right quadrant; single coronary artery in up to 18% of an autopsy series (PMID:837493, "Coronary arterial origin in persistent truncus arteriosus"). Coronary anomalies are an independent mortality risk factor after repair (Annals of Thoracic Surgery, S0003-4975(20)31908-1).
Non-confluent or absent (atretic) branch pulmonary artery — Van Praagh Type A3.
Additional common associated defects: secundum ASD, PDA, persistent left superior vena cava.

Clinical/physiologic phenotype (neonatal presentation)

Cyanosis (typically mild, due to complete intracardiac mixing) — often unresponsive to supplemental oxygen.
Signs of congestive heart failure: tachypnea with retractions/grunting, poor feeding, failure to thrive, lethargy, hepatomegaly, jugular venous distension — emerging as pulmonary vascular resistance (PVR) physiologically falls after birth and pulmonary overcirculation develops.
Bounding peripheral pulses (from diastolic runoff into the low-resistance pulmonary circuit and/or truncal regurgitation).
Harsh holosystolic murmur, ejection click, single loud S2 ± diastolic murmur if truncal regurgitation present.
Clubbing of extremities (later/chronic finding if unrepaired).
22q11.2-associated extracardiac phenotype (when syndromic): hypocalcemia/hypoparathyroidism (from parathyroid hypoplasia), thymic hypoplasia/aplasia with T-cell deficiency (profound athymia in ~1%), characteristic facial dysmorphism, cleft palate/velopharyngeal insufficiency, developmental delay/learning difficulties (>90%), and later-life psychiatric risk (autism spectrum disorder, schizophrenia).

Phenotype characteristics

Age of onset: congenital (present from birth); physiologic decompensation (CHF) typically manifests over the first days-to-weeks of life as PVR physiologically falls.
Severity/progression: Without surgical correction, essentially uniformly progressive and fatal in infancy — mortality before 2 months of life is common, with <20% one-year survival without surgery (StatPearls). By roughly 6 months–4 years of unrepaired pulmonary overcirculation, irreversible pulmonary vascular obstructive disease (Eisenmenger physiology) typically precludes safe surgical correction.
Frequency of key associated findings (population within PTA cohorts): truncal regurgitation ~50%; truncal stenosis ~25%; coronary anomalies 37–80%; 22q11.2 deletion 12–35% (up to ~27% in prenatally ascertained cohorts); right aortic arch ~21–36%; critical coarctation ~10%.

Quality of life impact

Adult long-term survivors of repaired PTA report quality of life (SF-6D) comparable to age-matched population controls and comparable to arterial-switch-operation survivors of transposition of the great arteries, despite a higher lifetime reoperation burden (PMID:31587054, "Long-term quality of life in adults following truncus arteriosus repair"). However, objective exercise capacity is mildly reduced in long-term survivors — peak VO2 averaging ~70% of predicted in one 12-patient cohort followed a median 19.7 years post-repair, correlating with truncal root/neo-aortic root dilation.

Suggested HPO terms

Truncus arteriosus (single arterial trunk) — verify exact CURIE via local OAK/HPO lookup
HP:0001636 Tetralogy of Fallot (for broader conotruncal-spectrum comparison, not PTA itself)
Truncal valve regurgitation / semilunar valve insufficiency — map to the closest HPO valve-regurgitation term
HP:0001635 Congestive heart failure
HP:0000969 Edema / HP:0001947 Hepatomegaly (CHF signs)
HP:0001513 Failure to thrive (or the age-specific FTT term)
HP:0000252 Microcephaly / HP:0000750 Developmental delay (22q11.2-associated)
HP:0002616 Aortic root aneurysm-type terms for late root dilation, if curated at disorder level

4. Genetic/Molecular Information

Causal genes/loci

Gene/Locus	OMIM	Role	Evidence
22q11.2 deletion region (TBX1)	188400 (DiGeorge)	Haploinsufficiency of TBX1, a T-box transcription factor expressed in pharyngeal/anterior heart field mesoderm, is the leading candidate for the outflow-tract phenotype	PMID:9316541; mouse Tbx1-null phenocopies human 22q11.2DS cardiac defects
NKX2-6	*611770	Homeodomain transcription factor in pharyngeal endoderm/OFT myocardium; biallelic homeodomain-disrupting variants cause autosomal recessive conotruncal disease including PTA	PMID:15649947; PMID:32198970
NKX2-5	600584	Cardiac transcription factor; variants found in PTA and interrupted aortic arch patients	cited in OMIM 217095
TMEM260	— (SHDRA)	Transmembrane protein of unknown precise mechanism; biallelic LOF variants (esp. East Asian founder c.1617del) cause structural heart defects + renal anomalies syndrome, with PTA as the most severe cardiac phenotype	PMID:38351237; PMC11043032; PMC11043042
FOXC1/FOXC2	—	Forkhead transcription factors; conditional neural-crest inactivation → outflow tract defects in mice	review context
GATA6	—	GATA-family transcription factor implicated in conotruncal malformation spectrum	review context

Pathogenic variant characteristics

Variant classes: 22q11.2 deletions are typically ~1.5–3 Mb microdeletions (detected by FISH/CMA/MLPA); NKX2-6 and TMEM260 disease-causing variants are largely biallelic loss-of-function/missense homeodomain-disrupting changes, consistent with autosomal recessive inheritance for these single-gene causes (in contrast to the typically de novo autosomal dominant 22q11.2 deletion).
Allele frequency: TMEM260 c.1617del carrier frequency ~0.36% in the Japanese population (a founder-type variant), essentially absent outside East Asian populations.
Somatic vs germline: All known causal variants for PTA are germline; 22q11.2 deletions are >90% de novo, with a minority inherited from a mildly-to-moderately affected parent (autosomal dominant, highly variable expressivity).
Functional consequence: predominantly loss of function / haploinsufficiency (TBX1, NKX2-6, TMEM260), consistent with a developmental dosage-sensitivity model for outflow-tract septation genes.

Modifier genes

Canonical Wnt/β-catenin signaling modifies Tbx1-driven outflow tract phenotypes: reduced β-catenin dosage significantly rescues cardiac outflow tract anomalies in a Tbx1 conditional-null 22q11.2DS mouse model, indicating Wnt/β-catenin acts genetically upstream of or in parallel with Tbx1 (PMID:28346476, PMC5386301).

Chromosomal abnormalities

22q11.2 microdeletion (most common) — the disease-defining structural variant of DiGeorge/velocardiofacial syndrome.
No other recurrent CNV is established as a major PTA cause in the literature reviewed, though isolated case reports of other conotruncal-associated microdeletions/duplications exist.

Epigenetic information

No PTA-specific DNA methylation or chromatin-state studies were identified in this search; this is an evidence gap.

5. Environmental Information

Toxin/teratogen exposure: retinoic acid pathway agonists (isotretinoin) implicated in conotruncal defect risk via dysregulation of RA signaling central to cardiac neural crest and OFT morphogenesis.
Maternal metabolic factors: pregestational (Type 1/Type 2) diabetes mellitus is the best-documented modifiable maternal risk factor, conferring >3-fold increased risk of PTA/TGA/tricuspid atresia (PMC10671602).
Infectious agents: no infectious etiology is established for PTA in the literature surveyed (unlike, e.g., congenital rubella syndrome's association with PDA/pulmonary stenosis).
Lifestyle factors: no PTA-specific lifestyle risk factor (smoking, alcohol) data were identified in this search; general CHD teratogen literature (e.g., alcohol, smoking) may apply non-specifically but was not directly quantified for PTA.

6. Mechanism / Pathophysiology

Causal chain: embryology → structural defect → hemodynamic consequence

Upstream (molecular/cellular, weeks 5–8 of human gestation): 1. Cardiac neural crest cell (CNCC) specification and migration from the dorsal neural tube through pharyngeal arches III, IV, and VI into the cardiac outflow tract, where CNCCs differentiate into the elastogenic smooth muscle of the aorticopulmonary (AP) septum. 2. Second heart field (SHF) mesodermal cells add to the elongating outflow tract myocardium; SHF–CNCC crosstalk (FGF8, BMP, Wnt/β-catenin signaling; transcription factors TBX1, NKX2-5, NKX2-6, GATA6) patterns conotruncal septation. 3. The two spiraling streams of outflow blood flow physically influence conal and truncal septal growth; the conotruncal ridges must fuse and spiral to form the definitive aortic and pulmonary valves plus the distal AP septum.

Point of failure: 4. Failure of AP septum formation / conotruncal ridge fusion — due to CNCC ablation/dysfunction (ablation experiments in chick models directly produce PTA and outflow tract elongation failure with defective cardiac looping), TBX1 haploinsufficiency in anterior heart field mesoderm (causing premature pro-differentiation gene expression), or loss of PDGFRα/PDGFRβ signaling in Pax3+ CNCCs (disrupting cell polarity/condensation into the OFT septum) — results in persistence of a single common arterial trunk rather than septation into separate aorta and pulmonary trunk (PMC9601305, "Single Cell Sequencing Reveals Mechanisms of Persistent Truncus Arteriosus Formation after PDGFRα and PDGFRβ Double Knockout in Cardiac Neural Crest Cells"). 5. The unseptated trunk necessarily overrides the ventricular septal defect because the conal septum (which normally also contributes to VSD closure) is likewise absent/malformed.

Downstream (organ/organism-level pathophysiology, postnatal): 6. At birth, complete mixing of pulmonary and systemic venous return occurs at the single ventricular-level VSD/truncal root, producing mild-to-moderate arterial desaturation (cyanosis) largely independent of any anatomic shunt restriction. 7. Because there is no pulmonary outflow obstruction in most cases, the ratio of pulmonary to systemic blood flow (Qp:Qs) is governed by the relative resistances of the pulmonary and systemic vascular beds. In the immediate newborn period, elevated PVR limits pulmonary flow; as PVR physiologically falls over the first days to weeks, pulmonary blood flow rises (pulmonary overcirculation), producing volume-overload congestive heart failure (tachypnea, poor feeding, hepatomegaly). 8. Truncal valve dysfunction — regurgitation (~50%) directly adds to ventricular volume load, compounding heart failure; stenosis (~25%) adds pressure overload/afterload to both ventricles simultaneously (since both ventricles eject through the single truncal valve), a more poorly tolerated lesion. 9. If uncorrected, chronic pulmonary overcirculation at systemic pressure (because the pulmonary bed is exposed to unrestricted systemic-level pressure via the single trunk) drives progressive pulmonary vascular remodeling and pulmonary hypertension, culminating in irreversible pulmonary vascular obstructive disease (Eisenmenger-type physiology) typically by early childhood, at which point surgical correction becomes contraindicated. 10. Coronary artery anomalies (present in a large minority-to-majority of cases due to the abnormal single-trunk geometry altering the normal aortic sinus template for coronary ostial development) create an additional substrate for perioperative and long-term myocardial ischemia/mortality risk.

Suggested GO / CL / UBERON terms

GO:0003151 outflow tract septum morphogenesis
GO:0003148 outflow tract septum morphogenesis (aorticopulmonary septation specifically — verify exact GO ID)
GO:0014032 neural crest cell development; GO:0001755 neural crest cell migration
GO:0060575 intestinal epithelial cell differentiation (n/a — not relevant; omit)
CL:0002350 cardiac neural crest cell (verify exact CL identifier)
CL:0000746 cardiac muscle cell
UBERON:0004151 outflow tract; UBERON:0002612 aorticopulmonary septum (verify against local ontology); UBERON:0002012 pulmonary trunk; UBERON:0001496 aortic valve / UBERON term for truncal/semilunar valve
CHEBI:50648 retinoic acid (teratogen)
CHEBI reference for prostaglandin E1/alprostadil: CHEBI:28464 (alprostadil) — verify exact ID

Molecular profiling

No large-scale disease-specific transcriptomic/proteomic/metabolomic human PTA dataset was identified in this search (expected given the rarity and typical neonatal surgical urgency of the condition); the strongest "omics" evidence base is single-cell sequencing of mouse CNCC-conditional-knockout models (PMC9601305), which characterizes the CNCC condensation-failure mechanism at single-cell resolution, and whole-genome/whole-exome sequencing cohorts underlying the TMEM260 and other monogenic discoveries (PMID:38351237).

7. Anatomical Structures Affected

Organ level

Primary: Heart — specifically the cardiac outflow tract/truncal root, truncal (semilunar) valve, interventricular septum (VSD), and great-vessel origins (aorta, main/branch pulmonary arteries, coronary arteries).
Secondary/complication-driven: Lungs (pulmonary vascular bed — overcirculation, pulmonary hypertension, pulmonary vascular obstructive disease); liver (hepatomegaly from right heart failure); systemic circulation broadly (volume overload).
Body systems involved: Cardiovascular (primary); when syndromic (22q11.2DS) — immune system (thymic hypoplasia/T-cell deficiency), endocrine (parathyroid hypoplasia/hypocalcemia), craniofacial/palatal, and neurodevelopmental/psychiatric systems.

Tissue and cell level

Cardiac neural crest-derived elastogenic smooth muscle of the (absent/malformed) aorticopulmonary septum.
Second heart field-derived myocardium of the outflow tract.
Truncal (semilunar) valve leaflet tissue — often dysplastic, with variable cusp number (bi-, tri-, or quadricuspid).
Coronary ostial/endothelial tissue — anomalous origin patterns.
Pulmonary vascular smooth muscle/endothelium — target of secondary remodeling in pulmonary hypertension.

Subcellular level

Not a classical subcellular/organelle disease; relevant subcellular biology is at the level of transcription factor nuclear function (TBX1, NKX2-5/2-6 as GO:0005667 transcription factor complex components) and membrane protein trafficking (TMEM260 as a transmembrane protein of incompletely defined subcellular role).

Localization

Structurally, the malformation is inherently midline/unilateral single structure (one trunk rather than two separate great vessels) rather than laterally paired; associated anomalies (e.g., right vs. left aortic arch) do carry laterality significance and are separately classified.

8. Temporal Development

Onset

Congenital — the structural lesion is fully established by the end of the embryonic period (~8 weeks gestation) as a failure of conotruncal septation.
Clinical onset of symptoms: typically within the first days to weeks of postnatal life, as physiologic PVR decline unmasks pulmonary overcirculation and heart failure; some degree of cyanosis may be evident immediately at birth.
Prenatal detectability: fetal echocardiography can detect PTA as early as 13 weeks, with routine second-trimester anomaly scanning (~18–22 weeks) as the typical diagnostic window; diagnostic accuracy for prenatal echocardiography is reported as high as 87%, though PTA can be confused with severe tetralogy of Fallot or pulmonary atresia with VSD on prenatal imaging.

Progression (natural history, unrepaired)

Early infancy: progressive congestive heart failure as PVR falls and pulmonary overcirculation develops.
Untreated mortality: death in infancy is probable without surgery; <20% one-year survival without repair; most deaths occur before 2 months of age.
By ~4 years of age (highly variable), irreversible pulmonary vascular obstructive disease (Eisenmenger physiology) typically develops in survivors, precluding safe corrective surgery — defining a critical treatment window in early infancy.
Course pattern: essentially uniformly progressive without intervention (not relapsing-remitting); with surgical correction, the course becomes one of staged/lifelong reintervention (conduit growth mismatch, valve degeneration) rather than cure.

Patterns / critical periods

The neonatal-to-early-infancy period is the critical therapeutic window: single-stage complete repair within the first month of life is now the preferred strategy (StatPearls), balancing operative risk against the risk of progressive pulmonary vascular disease if repair is delayed.
Late postoperative "critical periods": right ventricle-to-pulmonary-artery (RV-PA) conduits do not grow with the child, so somatic growth itself is a driver of reintervention need, concentrating reoperations in childhood/adolescence.

9. Inheritance and Population

Epidemiology

Incidence: ~7 per 100,000 live births annually (range cited 7–21/100,000 across sources).
Proportion of CHD: <1% of all congenital heart lesions; ~4% of critical congenital heart defects.
22q11.2 deletion syndrome background prevalence: ~1/2,150 live births generally (of which only a subset have PTA specifically).

Inheritance pattern

22q11.2 deletion (the dominant genetic cause): autosomal dominant, but >90% de novo; when inherited, transmission is dominant from an often mildly/variably affected parent. Variable expressivity and incomplete/variable penetrance for specific organ phenotypes (including the cardiac phenotype) is well documented — not every deletion carrier has a conotruncal cardiac defect.
NKX2-6-related and TMEM260-related (SHDRA) forms: autosomal recessive (biallelic variants identified in consanguineous families for NKX2-6; biallelic LOF for TMEM260).
Isolated/non-syndromic PTA: largely presumed multifactorial (polygenic + environmental), consistent with the broader "second/third-hit" model of CHD genetics.
Founder effect: TMEM260 c.1617del is a population-specific founder-type variant essentially restricted to Japanese/Korean populations.
Consanguinity: relevant specifically to the recessive NKX2-6-associated families, in which autozygosity mapping was used for gene discovery.

Population demographics

Sex ratio: no significant sex predilection established; some series note a slight, non-significant male predominance.
Race/ethnicity: no broad racial predilection reported for PTA overall, though the TMEM260 founder variant creates an ethnicity-specific (East Asian) genetic subgroup.
Geographic distribution: no endemic geographic clustering beyond the population-genetic TMEM260 founder effect in Japan/Korea.
Termination-of-pregnancy rates after prenatal diagnosis: substantial — one series reported 68% of fetuses diagnosed before 24 weeks did not survive to birth (spontaneous fetal death or elective termination); another reported 41.2% elective termination rate, reflecting the severity of prenatal counseling discussions.

10. Diagnostics

Prenatal

Fetal echocardiography — primary prenatal diagnostic modality; detects the single arterial trunk, large VSD, and pulmonary artery origin pattern; feasible from as early as 13 weeks, routinely by 18–22 weeks; diagnostic accuracy up to 87%, with differential challenges vs. severe tetralogy of Fallot and pulmonary atresia with VSD.
Prenatal genetic testing — 22q11.2 deletion testing (e.g., via chromosomal microarray, FISH, or NIPT-adjacent approaches) recommended whenever PTA is suspected prenatally, given the ~12–35% (up to 27% in prenatal cohorts) 22q11.2DS association.

Postnatal clinical/imaging tests

Transthoracic echocardiography — primary postnatal diagnostic and surveillance modality (truncal valve morphology/function, VSD, branch PA origins, coronary origins where visualizable).
Cardiac MRI or CT angiography (CTA) — used to delineate coronary anatomy, branch pulmonary artery anatomy, and aortic arch anomalies (interruption/coarctation) not fully resolved by echo.
Cardiac catheterization — generally reserved for interventional procedures (e.g., balloon angioplasty/stenting of branch PA or conduit stenosis) rather than primary diagnosis.
Physical exam findings supporting diagnosis: harsh holosystolic murmur, ejection click, single loud S2, ± diastolic murmur (truncal regurgitation), bounding pulses, cyanosis/clubbing, hepatomegaly.

Genetic testing

Chromosomal microarray (CMA) / FISH for 22q11.2 deletion — first-line genetic test given the high pretest probability; FISH historically used for targeted 22q11.2 detection, now largely supplanted/complemented by CMA for genome-wide resolution.
Gene panel / exome sequencing — indicated when 22q11.2 deletion testing is negative, particularly to identify NKX2-6, NKX2-5, TMEM260 (especially in patients of East Asian ancestry, where TMEM260 targeted testing or panel inclusion is specifically warranted), or other monogenic conotruncal-disease genes.
Karyotyping — of historical/adjunctive value for detecting other chromosomal abnormalities.

Clinical diagnostic criteria / differential diagnosis

No formal DSM/ICD-style clinical scoring criteria exist beyond echocardiographic/anatomic definition. Key differentials: severe tetralogy of Fallot with pulmonary atresia, and pulmonary atresia with VSD and major aortopulmonary collateral arteries (MAPCAs) — both can closely mimic PTA, especially prenatally, and require careful distinction of pulmonary arterial origin (from the common trunk vs. from the descending aorta/collaterals).

Screening

No population-level newborn screening test specifically targets PTA; however, pulse oximetry-based critical congenital heart disease (CCHD) newborn screening, now standard in many health systems, will typically flag PTA (and other critical CHDs) via low peripheral oxygen saturation, prompting urgent echocardiography.

11. Outcome / Prognosis

Survival without treatment

Mortality is probable in infancy without surgical correction; <20% survive to one year unrepaired (StatPearls).

Survival with surgical repair

Perioperative/hospital mortality: ~6% in a representative single-center series (3/50 patients) — two deaths from pulmonary hypertensive crisis, one from pneumonia (PLOS ONE, PMC4713837).
Actuarial survival: 87.7% at both 1 and 5 years post-repair in that series; other multicenter series report 20-year survival >80% after primary repair (StatPearls).
Very long-term (30-year) survival: reported at 68.5% in one long-term single-center cohort, with truncal valve regurgitation identified as a key risk factor for both mortality and reoperation.
Freedom from reoperation: ~92.9% at 5 years in one series; another reports freedom from RV-PA conduit/branch-PA reoperation of only 59% at 5 years and 28% at 10 years, and ~75% of patients require reintervention by 10 postoperative years — reoperation is essentially inevitable given somatic outgrowth of non-growing conduits.

Prognostic/risk factors

Significant preoperative truncal valve regurgitation — independent risk factor for mortality.
Quadricuspid truncal valve morphology, truncal valve insufficiency at diagnosis, and truncal valve intervention at index repair — associated with increased reoperation risk.
RV-PA conduit size ≤11 mm — associated with higher risk of early catheter-based reintervention/reoperation.
Coronary artery anomalies (ostial stenosis, intramural course, juxtacommissural origin) — independently associated with increased mortality after repair.
Late referral / delayed repair — associated with higher risk of postoperative pulmonary hypertensive crisis.

Functional/quality-of-life outcomes

Nearly all long-term survivors are in NYHA functional class I–II.
Adult QOL (SF-6D) is comparable to general-population controls and to arterial-switch-operation (TGA) survivors, despite the higher truncus reoperation burden.
Exercise capacity is mildly reduced long-term (peak VO2 ~70% of predicted in one cohort), correlating with truncal/neo-aortic root dilation.

Complications

Early postoperative: pulmonary hypertensive crisis, low cardiac output syndrome, right bundle branch block, supraventricular tachycardia, mediastinal bleeding, pleural effusion, pneumothorax, cardiac tamponade. Late: conduit stenosis/regurgitation requiring replacement, truncal (neo-aortic) valve regurgitation/stenosis requiring repair or replacement, arrhythmia, and (in unrepaired or late-presenting patients) irreversible pulmonary vascular disease.

12. Treatment

Medical stabilization (pre-/peri-operative)

Diuretics (loop diuretics, thiazides) for congestive heart failure control. — Suggested NCIT: NCIT:C15986 (Pharmacotherapy) + therapeutic_agent class (diuretic).
Avoidance of supplemental oxygen where possible, since it lowers PVR and worsens pulmonary overcirculation.
Prostaglandin E1 (alprostadil) — used selectively when ductal patency is needed to support systemic perfusion (e.g., in the presence of critical coarctation or interrupted arch); dosed 0.01–0.1 mcg/kg/min IV; ~82% of infants show effective clinical improvement at the initial 0.1 mcg/kg/min dose, with effect maintained at reduced maintenance doses; key adverse effects include apnea, peripheral vasodilation, and hypotension (StatPearls: Alprostadil, NBK542217). — Suggested NCIT: NCIT:C15986 Pharmacotherapy; therapeutic_agent CHEBI (alprostadil/prostaglandin E1, verify exact CHEBI ID e.g. CHEBI:28464).
Correction of metabolic/electrolyte derangements.

Surgical repair (definitive treatment)

Single-stage complete primary repair, preferably within the first month of life, comprising: separation of the pulmonary arterial supply from the truncal root; VSD patch closure (baffling the truncal/aortic outflow to the left ventricle); RV-to-PA conduit (homograft, valved or non-valved conduit) reconstruction of the right ventricular outflow tract; and concurrent repair of any truncal valve regurgitation/stenosis and aortic arch anomaly (coarctation repair/arch reconstruction) as needed. — Suggested NCIT: NCIT:C15329 (Surgical Procedure) / NCIT:C16186 (Orthopedic — N/A) → more specifically a cardiac surgical repair term; therapeutic_modality: SURGERY.
Staged repair (e.g., pulmonary artery banding followed by delayed correction) is not routinely recommended due to higher morbidity/mortality compared with primary single-stage repair.
Truncal valve repair or replacement — performed at index repair or later, for significant regurgitation/stenosis; a documented risk factor for reoperation when performed at index surgery (reflecting valve severity rather than a causal effect of the intervention itself).
Reintervention: transcatheter balloon angioplasty/stenting of conduit or branch pulmonary artery stenosis; surgical conduit replacement as the child outgrows the original conduit — an expected, near-universal component of lifelong management (freedom from reintervention only 28% at 10 years in some series).

Genetic counseling / multidisciplinary supportive care

Genetic counseling strongly recommended given the 22q11.2 deletion association (recurrence risk implications, extracardiac surveillance needs). — NCIT:C15240 Genetic Counseling.
Supportive/multidisciplinary care: pediatric cardiology, cardiac surgery, intensive care, genetics, radiology, nursing, respiratory therapy, social work, and (with age) transition to adult congenital heart disease (ACHD) specialty care; mental health support given the psychosocial burden of chronic cardiac disease and repeated procedures.
Immunologic/endocrine management in 22q11.2DS-associated cases: calcium/vitamin D management for hypoparathyroidism-driven hypocalcemia; immunologic monitoring/prophylaxis for T-cell deficiency; avoidance of live vaccines in significant T-cell immunodeficiency.

Experimental / emerging

No PTA-specific gene therapy, cell therapy, or targeted molecular therapeutic was identified in this search — treatment remains fundamentally surgical/structural, consistent with the anatomic nature of the defect. A computational modeling study (arXiv:2601.08932, "Simulations Predict Improved Valve Performance Without Direct Leaflet Intervention After Neonatal Truncus Arteriosus Repair") represents an emerging in-silico approach to optimizing surgical valve/conduit strategy rather than a new therapeutic modality per se.

Treatment outcomes

See Section 11 (Outcome/Prognosis) for detailed survival, reoperation, and functional-outcome statistics associated with each treatment strategy.

13. Prevention

Primary prevention

Optimization of pregestational maternal glycemic control in diabetic mothers is the most directly actionable primary-prevention lever identified in this literature, given the >3-fold increased conotruncal-defect risk associated with maternal pregestational diabetes.
Avoidance of retinoic acid/isotretinoin exposure during pregnancy (established teratogen avoidance, standard obstetric practice — isotretinoin carries FDA pregnancy category X / iPLEDGE program restrictions generally, not PTA-specific).
General periconceptional folic acid supplementation is standard CHD-risk-reduction practice, though not specifically quantified for PTA in the literature surveyed.

Secondary prevention / screening

Prenatal ultrasound anomaly screening (routine second-trimester fetal echocardiography) enables early detection, allowing informed counseling, delivery planning at a cardiac surgical center, and prostaglandin availability at birth if arch anomalies are present.
22q11.2 deletion testing upon prenatal or postnatal PTA diagnosis enables early identification of associated hypocalcemia, immunodeficiency, and syndromic features, allowing proactive endocrine/immunologic management.
Newborn pulse oximetry CCHD screening provides a postnatal safety net for cases not detected prenatally.

Tertiary prevention

Timely single-stage neonatal surgical repair (within the first month of life) is itself the principal tertiary-prevention strategy — preventing the otherwise inevitable progression to irreversible pulmonary vascular obstructive disease.
Structured lifelong cardiology follow-up (serial echocardiography, conduit/valve surveillance) to detect and intervene on conduit stenosis, valve regurgitation, and arrhythmia before they cause irreversible ventricular dysfunction.

Genetic counseling / reproductive planning

Recommended for families of an affected child, particularly given the identifiable 22q11.2 deletion (autosomal dominant, variable expressivity, ~50% recurrence risk if a parent carries the deletion) and the autosomal recessive NKX2-6/TMEM260 forms (25% recurrence risk per pregnancy, elevated with consanguinity).

14. Other Species / Natural Disease

Naturally occurring PTA-like disease is not well-documented as a spontaneous veterinary clinical entity in the sources surveyed (unlike, e.g., patent ductus arteriosus, which is common in dogs); this literature search did not identify OMIA entries or veterinary case series specifically for spontaneous PTA in companion or production animals. This is likely because complete conotruncal septation failure is generally not compatible with survival to veterinary presentation in most species, or is under-reported. (This should be flagged as an evidence gap requiring dedicated OMIA/veterinary-literature search if the KB entry requires this section populated.)
Comparative embryology is well studied experimentally (see Model Organisms below) even though spontaneous natural disease reports are sparse.

15. Model Organisms

Mouse models

Tbx1 conditional/null mutant mice — the primary genetic model of 22q11.2DS-associated PTA. Tbx1-null mice show neonatal lethality with cleft palate, abnormal inner ears, absent thymus and parathyroid glands, and persistent truncus arteriosus, closely phenocopying the human 22q11.2 deletion syndrome cardiac phenotype. Graded hypomorphic Tbx1 dosage (100%→2%) across allelic series produces a dosage-dependent spectrum of outflow tract defects — PTA at the most severe end, through tetralogy of Fallot and double-outlet right ventricle at intermediate dosage — directly modeling human phenotypic variability from a single haploinsufficient locus.
Tbx1 conditional-null + reduced β-catenin dosage — genetic rescue experiment demonstrating that lowering Wnt/β-catenin pathway dosage significantly rescues Tbx1-mutant outflow tract anomalies, establishing an epistatic/modifier relationship (PMID:28346476).
Pax3 Splotch (Sp1H) mutant mice — classic neural-crest-deficient model; homozygotes show failure of truncus arteriosus septation and aortic arch-derived vessel anomalies, historically one of the first genetic confirmations of the CNCC-dependence of conotruncal septation (PMID:2619088, "Persistent truncus arteriosus in the Splotch mutant mouse").
PDGFRα/PDGFRβ double-knockout in Pax3+ cardiac neural crest cells — recent (single-cell RNA-seq-characterized) model showing that combined loss of platelet-derived growth factor receptor signaling in CNCCs disrupts CNCC condensation/polarity within the outflow tract septum, producing PTA and elucidating a cell-biological (cytoskeletal/adhesion) mechanism distinct from pure transcription-factor loss (PMC9601305).
Cardiac neural crest surgical ablation (chick, extrapolated conceptually to mammalian models) — ablation of the CNC in chick embryos directly produces PTA with failed outflow tract elongation and defective cardiac looping, establishing the foundational CNCC-dependence paradigm for conotruncal septation.

Comparative/cross-species notes

Chick embryo — the classical experimental model for CNC ablation studies of outflow tract septation; closely models the mammalian (including human) requirement for CNC-directed septation.
Xenopus — notably, cardiac neural crest is dispensable for outflow tract septation in Xenopus, a striking cross-species divergence from chick/mouse/human biology, underscoring that CNCC-dependence of septation is not universally conserved across vertebrates and that Xenopus is a poor model for PTA specifically.
Zebrafish — the zebrafish outflow tract does not become remodeled or septated at all (unlike higher vertebrates), so zebrafish cannot model true PTA; zebrafish CNC ablation instead alters ventricular myocardial cardiomyocyte number rather than septation. Zebrafish remain useful for dissecting general second-heart-field/outflow-tract progenitor biology (e.g., nkx2.5+ anterior lateral plate mesoderm-derived progenitors), but this is a clear human-model-mismatch consideration: zebrafish outflow tract biology should not be over-extrapolated to human septation-failure mechanisms without chick/mouse cross-validation.

Applications and limitations

Mouse Tbx1-dosage allelic series is the best-validated model for dosage-dependent phenotypic severity, directly relevant to the variable cardiac penetrance seen in human 22q11.2 deletion carriers.
Chick CNC-ablation remains the classical model for mechanistic dissection of CNCC contribution to septation but is less genetically tractable than mouse for modern single-cell/genomic approaches.
No model organism to date fully recapitulates the human TMEM260-SHDRA phenotype (renal + cardiac); this represents an open modeling gap.

Summary of Key Ontology Term Suggestions for KB Curation

Domain	Suggested term(s) — verify exact CURIE/label via OAK before committing
MONDO	MONDO:0018072 (Persistent truncus arteriosus / common arterial trunk)
Orphanet	ORPHA:3384
OMIM	217095 (Conotruncal Heart Malformations); 188400 (DiGeorge syndrome, comorbid)
ICD-10-CM	Q20.0
HGNC genes	TBX1, NKX2-6, NKX2-5, TMEM260, FOXC1, FOXC2, GATA6
GO (process)	outflow tract septum morphogenesis; neural crest cell migration; canonical Wnt signaling pathway
CL (cell type)	cardiac neural crest cell; second heart field cardiomyocyte progenitor
UBERON (anatomy)	outflow tract; aorticopulmonary septum; truncal/semilunar valve; pulmonary trunk
CHEBI (chemical)	retinoic acid; alprostadil (prostaglandin E1)
NCIT (treatment)	Surgical Procedure; Pharmacotherapy; Genetic Counseling
HPO (phenotype)	Truncus arteriosus (verify exact CURIE); Congestive heart failure; Failure to thrive; Developmental delay (22q11.2-associated)

Notable Evidence Gaps (flag for curators)

No spontaneous veterinary/natural-disease literature was located for PTA specifically — Section 14 is thin and should be treated as a gap pending dedicated OMIA search.
No PTA-specific epigenomic/methylation dataset was identified.
Exact HPO CURIE for "truncus arteriosus" returned inconsistent results across search sources and must be confirmed directly via runoak -i sqlite:obo:hp before use.
Human transcriptomic/single-cell data for PTA cardiac tissue itself (as opposed to mouse CNCC knockout models) does not appear to be well represented in the literature surveyed — mechanistic single-cell evidence is currently MODEL_ORGANISM-only, a relevant HUMAN_MODEL_MISMATCH consideration for pathophysiology curation.

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Persistent Truncus Arteriosus (PTA) — Comprehensive Disease Characteristics Research Report

1. Disease Information

2. Etiology

Disease Causal Factors

Genetic Risk Factors

Environmental Risk Factors

Protective Factors

Gene-Environment Interactions

3. Phenotypes

Cardiac structural phenotype (congenital/present at birth; category: physical malformation)

Clinical/physiologic phenotype (neonatal presentation)

Phenotype characteristics

Quality of life impact

Suggested HPO terms

4. Genetic/Molecular Information

Causal genes/loci

Pathogenic variant characteristics

Modifier genes

Chromosomal abnormalities

Epigenetic information

5. Environmental Information

6. Mechanism / Pathophysiology

Causal chain: embryology → structural defect → hemodynamic consequence

Suggested GO / CL / UBERON terms

Molecular profiling

7. Anatomical Structures Affected

Organ level

Tissue and cell level

Subcellular level

Localization

8. Temporal Development

Onset

Progression (natural history, unrepaired)

Patterns / critical periods

9. Inheritance and Population

Epidemiology

Inheritance pattern

Population demographics

10. Diagnostics

Prenatal

Postnatal clinical/imaging tests

Genetic testing

Clinical diagnostic criteria / differential diagnosis

Screening

11. Outcome / Prognosis

Survival without treatment

Survival with surgical repair

Prognostic/risk factors

Functional/quality-of-life outcomes

Complications

12. Treatment

Medical stabilization (pre-/peri-operative)

Surgical repair (definitive treatment)

Genetic counseling / multidisciplinary supportive care

Experimental / emerging

Treatment outcomes

13. Prevention

Primary prevention

Secondary prevention / screening

Tertiary prevention