👪

Inheritance

1

Autosomal recessive inheritance HP:0000007

TDD is inherited in an autosomal recessive manner. Parents of an affected child are typically heterozygous carriers, giving a 25% recurrence risk per pregnancy. Penetrance for biallelic severe loss of function appears high, but expressivity is markedly variable - including between siblings who share a genotype - so genotype does not reliably predict severity. Consanguinity increases the chance of homozygosity but is not required; compound heterozygosity and unmasking by a 22q11.2 deletion in trans are both recognized routes to biallelic loss.

Autosomal recessive inheritance

Show evidence (4 references)

PMID:38829177 SUPPORT Human Clinical

"TANGO2 deficiency disorder (TDD) is a rare, autosomal recessive condition caused by pathogenic variants in TANGO2"

States the mode of inheritance.

PMID:31339582 SUPPORT Human Clinical

"All nine subjects carried autosomal recessive TANGO2 mutations."

Confirms recessive segregation across an independent multi-family series.

PMID:42115085 SUPPORT Other

"Intrafamilial phenotypic variability and overlapping manifestations with other metabolic diseases complicate timely and accurate diagnosis."

Supports the variable-expressivity statement. Evidence source is OTHER because this is a review article.

+ 1 more reference

⚙

Pathophysiology

13

Catabolic Stress Exposure

TDD is a stress-unmasked disorder: the biallelic genotype is present from conception, but the acute phenotype requires an extrinsic catabolic challenge. Established precipitants are intercurrent (especially febrile or viral) illness, fasting, dehydration, reduced oral intake, excessive heat, overexertion and a ketogenic diet. Some anaesthetic agents and, more tentatively, L-carnitine have been proposed as additional triggers, which makes specialist perioperative planning important.

Downstream

Catabolic-Stress Metabolic Decompensation Catabolic challenge raises substrate demand and shifts fuel use toward fatty acids in a system that cannot sustain that shift, converting the latent metabolic vulnerability into an acute crisis.

Show evidence (2 references)

PMID:29369572 SUPPORT Other

"Triggers for TANGO2 spells and acute metabolic crises including fasting, dehydration, overexertion, exposure to excessive heat, ketogenic diet, and infections."

Enumerates the established crisis precipitants. Evidence source is OTHER because this is a GeneReviews expert-consensus chapter rather than a primary study.

PMID:32929747 SUPPORT Human Clinical

"We show previously uncharacterized triggers of metabolic crises in TANGO2 patients, such as some anesthetics and possibly l-carnitine."

Adds anaesthetic exposure as a trigger identified in the 20-patient French cohort; the l-carnitine association is explicitly hedged by the authors.

TANGO2 Loss of Function

Biallelic loss-of-function variants in TANGO2 - multiexon deletions (predominantly the recurrent exon 3-9 deletion), nonsense, frameshift, canonical splice-site and missense alleles - abolish or severely reduce TANGO2 protein. Purified TANGO2 binds acyl-coenzyme A, and mutation of its conserved NRDE motif abolishes that binding, leading its authors to propose that TANGO2 is an acyl-CoA-binding protein of the mitochondrial lumen. Separate imaging work localizes it predominantly to mitochondria and partially to mitochondrial sites juxtaposed to lipid droplets and the endoplasmic reticulum. An independent line of work identifies TANGO2 as a binding partner of the small heat-shock protein CRYAB that restrains desmin intermediate-filament aggregation, so the precise primary biochemical activity remains an area of active disagreement.

TANGO2 hgnc:25439

fatty-acyl-CoA binding GO:0000062 ↓ DECREASED

mitochondrion GO:0005739 lipid droplet GO:0005811

Downstream

Lipid and Acyl-CoA Homeostasis Failure Loss of acyl-CoA handling starves downstream acylation and lipid-remodelling reactions.

Impaired ER-to-Golgi Membrane Trafficking Loss of TANGO2 slows secretory-pathway cargo transit, the phenotype for which the gene was originally named.

Oligodendroglial Lipid Dysregulation and Cerebellar Myelin Loss Cell-type-specific mouse deletion shows that TANGO2 loss in oligodendroglia is by itself sufficient to disturb phospholipid metabolism and myelin maintenance.

Show evidence (5 references)

PMID:26805782 SUPPORT Human Clinical

"By exome sequencing, we identified three different bi-allelic truncating mutations in TANGO2 in three unrelated individuals with infancy-onset episodic metabolic crises characterized by encephalopathy, hypoglycemia, rhabdomyolysis, arrhythmias, and laboratory findings suggestive of a defect in..."

The gene-discovery paper establishing biallelic truncating TANGO2 variants as the cause of the disorder.

PMID:40015245 SUPPORT In Vitro

"We further show that purified TANGO2 binds acyl-coenzyme A, and mutations in the highly conserved NRDE sequence of TANGO2 inhibit this binding."

Biochemical evidence assigning TANGO2 an acyl-CoA-binding molecular function.

PMID:40015245 SUPPORT In Vitro

"we demonstrate that TANGO2 localizes to the mitochondrial lumen via a structural region containing LIL residues"

Localizes the protein to the mitochondrial lumen, supporting the mitochondrial cellular-component annotation.

+ 2 more references

Impaired ER-to-Golgi Membrane Trafficking

Fibroblasts from affected individuals show a significant delay in movement of secretory cargo between the endoplasmic reticulum and the Golgi apparatus, attributable to loss of TANGO2 function, together with altered mitochondrial morphology. This trafficking arm is the defect most directly rescued by vitamin B5 in human cells, which is why it is retained as a distinct node even though its quantitative contribution to the acute crisis is not established.

fibroblast CL:0000057

endoplasmic reticulum to Golgi vesicle-mediated transport GO:0006888 ↓ DECREASED

endoplasmic reticulum GO:0005783 Golgi apparatus GO:0005794

Downstream

Catabolic-Stress Metabolic Decompensation Secretory and membrane-transport impairment is proposed to reduce the cell's capacity to remodel membranes under stress; the causal weight of this edge relative to the lipid arm is not established.

Show evidence (3 references)

PMID:32909282 SUPPORT In Vitro

"there is a significant delay in the movement of cargo between the endoplasmic reticulum and the Golgi"

Direct measurement of the trafficking delay in patient-derived fibroblasts.

PMID:32909282 SUPPORT In Vitro

"We further show that a portion of TANGO2 protein localizes to the mitochondria through a necessary but not sufficient stretch of amino acids at the amino terminus of the protein."

Supports the dual trafficking-plus-mitochondrial account of the protein referenced in this node's description.

PMID:31339582 SUPPORT In Vitro

"Proteomic analysis in fibroblasts revealed significant changes in components of the mitochondrial fatty acid oxidation, plasma membrane, endoplasmic reticulum-Golgi network and secretory pathways."

Independent proteomic corroboration that the ER-Golgi and secretory compartments are perturbed.

Lipid and Acyl-CoA Homeostasis Failure

Quantitative lipidomics of TANGO2-null HepG2 cells and patient fibroblasts shows a marked rise in lysophosphatidic acid with a reciprocal fall in its biosynthetic product phosphatidic acid, consistent with insufficient acyl-CoA available for LPA acylation. Triglyceride and lysophospholipid pools rise, the free fatty acid pool expands, and lipid droplets enlarge. The resulting defect in fatty-acid handling generates high levels of reactive oxygen species and promotes lipid peroxidation. Critically, these changes are exacerbated by nutrient starvation - the biochemical correlate of the clinical fasting trigger - and are reversed by vitamin B5 supplementation, which restores the coenzyme A precursor pool.

glycerolipid metabolic process GO:0046486 ⚠ ABNORMAL phospholipid biosynthetic process GO:0008654 ↓ DECREASED cellular response to reactive oxygen species GO:0034614 ↑ INCREASED

lipid droplet GO:0005811

Downstream

Impaired Mitochondrial Fatty-Acid Oxidation and Energy Reserve Restricted acyl-CoA supply and disordered membrane phospholipid composition degrade the capacity of mitochondria to oxidize fatty acids and to sustain ATP output under load.

Show evidence (5 references)

PMID:36961129 SUPPORT In Vitro

"Quantitative lipidomics revealed a marked increase in lysophosphatidic acid (LPA) and a concomitant decrease in its biosynthetic precursor phosphatidic acid (PA). These changes were exacerbated in nutrient-starved cells."

The core lipidomic signature, and its worsening under the nutrient stress that clinically triggers crises.

PMID:36961129 SUPPORT In Vitro

"The defect in acyl-CoA availability impacts the metabolism of many other fatty acids, generates high levels of reactive oxygen species, and promotes lipid peroxidation."

Links the acyl-CoA defect to oxidative injury, the bridge from lipid imbalance to tissue damage.

PMID:38718569 SUPPORT In Vitro

"we found profound changes in the lipid profile of human TANGO2-deficient cells"

Independent lipidomic replication of the lipid-profile abnormality in human TANGO2-deficient cells.

+ 2 more references

Impaired Mitochondrial Fatty-Acid Oxidation and Energy Reserve

Mutant fibroblasts show a functional defect of palmitate-dependent respiration, and CRISPR-engineered TANGO2-null iPSC-derived cardiomyocytes have normal bioenergetics on glucose but a profound fall in ATP production rate and ATP/ADP ratio when forced to use palmitate, worsened by 24-hour fasting. Muscle histology and respiratory-chain studies in patients are often unremarkable at baseline, and plasma acylcarnitines and FGF-21 are usually normal between episodes: the deficit is a conditional, substrate-dependent loss of energy reserve rather than a constitutive respiratory-chain enzyme deficiency. Autophagy and mitophagy are additionally impaired on starvation, limiting the clearance of damaged organelles. This node conforms to the module's toxic-metabolite/energy-deficit stage on the energy-deficit arm; the accumulating species in TDD are lysophospholipids and free fatty acids rather than a classical organic acid.

fatty acid beta-oxidation GO:0006635 ↓ DECREASED autophagy GO:0006914 ↓ DECREASED

mitochondrion GO:0005739

Downstream

Catabolic-Stress Metabolic Decompensation Once fatty acids become the dominant fuel during fasting or febrile illness, the exhausted energy reserve tips high-demand tissues into overt decompensation.

Show evidence (4 references)

PMID:26805782 SUPPORT In Vitro

"Investigation of palmitate-dependent respiration in mutant fibroblasts showed evidence of a functional defect in mitochondrial β-oxidation."

First functional demonstration of impaired fatty-acid oxidation in patient cells.

PMID:42389941 SUPPORT In Vitro

"using palmitate as energy substrate triggered a profound reduction in cellular ATP production rate and decreased ATP/ADP ratios in TANGO2-/- hiPSC-CMs, exacerbated by 24-hour fasting. This crisis was prevented by 2-week treatment with vitamins B5 and B9."

Shows the deficit is substrate-conditional (present on palmitate, absent on glucose) and fasting-amplified, and that B-vitamin pretreatment prevents it.

PMID:32929747 SUPPORT Human Clinical

"Mechanistically, TANGO2 disease is unlikely to originate from a primary mitochondrial defect. Rather, we suggest that mitochondrial defects are secondary to strong extrinsic triggers in TANGO2 deficient patients."

Constrains the claim: this node is a secondary, stress-dependent mitochondrial deficit, not a primary respiratory-chain disorder. Recorded as PARTIAL because it refutes the strong version of the mitochondrial hypothesis while supporting the conditional version modelled here.

+ 1 more reference

Catabolic-Stress Metabolic Decompensation

The acute crisis is the shared central effector of the disorder. It manifests as hypoglycaemia, lactic and metabolic acidosis, markedly elevated creatine kinase and transaminases, and encephalopathy, and it converts the latent cellular lesion into simultaneous multi-organ injury of skeletal muscle, brain and heart. Between episodes, standard metabolic screening is frequently normal, so a normal baseline workup does not exclude the diagnosis.

glucose homeostasis GO:0042593 ⚠ ABNORMAL fatty acid metabolic process GO:0006631 ⚠ ABNORMAL

Downstream

Skeletal Myofiber Necrosis and Rhabdomyolysis Energy failure in the highest-demand striated tissue produces myofiber necrosis with release of creatine kinase and myoglobin.

Acute Metabolic Encephalopathy Hypoglycaemia, acidosis and neuronal energy failure produce acute encephalopathy and seizures during the crisis.

Cardiomyocyte ATP Depletion and Repolarization Instability Cardiomyocytes forced onto fatty-acid fuel during the crisis lose ATP and destabilize repolarization.

Show evidence (3 references)

PMID:32909282 SUPPORT Other

"TANGO2 variants result in a complex disease phenotype consisting of recurrent crisis-induced rhabdomyolysis, encephalopathy, seizures, lactic acidosis, hypoglycemia, and cardiac arrhythmias."

Enumerates the biochemical and clinical content of the decompensated state. Evidence source is OTHER because this is the background statement of an in vitro trafficking study, not its own clinical observation.

PMID:31339582 SUPPORT Human Clinical

"Transport And Golgi Organization protein 2 (TANGO2) deficiency has recently been identified as a rare metabolic disorder with a distinct clinical and biochemical phenotype of recurrent metabolic crises, hypoglycemia, lactic acidosis, rhabdomyolysis, arrhythmias, and encephalopathy with cognitive decline."

Independent characterization of the same decompensation syndrome.

PMID:32929747 SUPPORT Human Clinical

"Unexpectedly, plasma acylcarnitines, plasma FGF-21, muscle histology, and mitochondrial spectrometry were mostly normal."

Supports the statement that interictal biochemical screening is typically unrevealing.

Skeletal Myofiber Necrosis and Rhabdomyolysis

Skeletal muscle is the tissue most consistently injured during crises. Myofibers undergo necrosis with release of creatine kinase and myoglobin, producing myoglobinuria and, when severe, acute kidney injury. Zebrafish tango2 mutants reproduce this stress-conditional muscle vulnerability, showing increased skeletal-muscle susceptibility to extrinsic triggers; the same model links the injury to failed autophagy and mitophagy. Chronic myopathic change with endomysial fibrosis is documented at the mild end of the spectrum.

skeletal muscle cell CL:0000188

lipid catabolic process GO:0016042 ⚠ ABNORMAL

skeletal muscle tissue UBERON:0001134

Show evidence (3 references)

PMID:37577943 SUPPORT Model Organism

"the loss of Tango2 in zebrafish results in growth defects, early lethality and increased susceptibility of skeletal muscle defects in response to extrinsic triggers, similar to TANGO2-deficient patients"

Model-organism recapitulation of trigger-dependent skeletal muscle injury.

PMID:39722856 SUPPORT Model Organism

"rhabdomyolysis features of tango2 knockdown were associated with autophagy and mitophagy defects in zebrafish"

Mechanistically connects the muscle injury to impaired autophagic clearance.

PMID:37119590 SUPPORT Human Clinical

"Muscle histology two years later revealed increased endomysial fibrosis and other myopathic changes."

Documents chronic structural muscle damage persisting between crises in a human case.

Acute Metabolic Encephalopathy

During crises, neuronal energy failure compounded by hypoglycaemia and lactic acidosis produces acute encephalopathy ranging from lethargy and disorientation to seizures and coma. Unlike the classical intoxication-type inborn errors, ammonia neurotoxicity is not the dominant driver in TDD; the conformance to the module is therefore on the shared energy-failure and acidosis route to acute encephalopathy rather than on the ammonia-glutamine astrocyte-swelling route.

neuron CL:0000540

brain UBERON:0000955

Downstream

Progressive Neurodegeneration and Regression Repeated encephalopathic episodes contribute to stepwise loss of acquired skills superimposed on the baseline neurodevelopmental course.

Show evidence (2 references)

PMID:26805782 SUPPORT Human Clinical

"three unrelated individuals with infancy-onset episodic metabolic crises characterized by encephalopathy, hypoglycemia, rhabdomyolysis, arrhythmias"

Places encephalopathy within the crisis syndrome alongside hypoglycaemia.

PMID:30245509 SUPPORT Human Clinical

"Primary features include metabolic crisis with rhabdomyolysis, encephalopathy, intellectual disability, seizures, and cardiac arrhythmias."

Independent case-series confirmation that encephalopathy is a primary crisis feature.

Cardiomyocyte ATP Depletion and Repolarization Instability

In TANGO2-null iPSC-derived cardiomyocytes, the palmitate-driven collapse of the ATP/ADP ratio prolongs the action potential; the prolongation is abolished by intracellular delivery of Mg-ATP or creatine kinase, showing it is energy-dependent rather than a primary channel defect. The metabolic crisis upregulates TRPM4, an ATP- and calcium-regulated cation channel, and TRPM4 knockdown or block prevents action-potential prolongation without correcting the energy deficit. L-type calcium channel inhibition with verapamil also prevents prolongation by normalizing ATP/ADP and intracellular calcium handling. Conformance to the channelopathy module is declared here on the altered-action-potential/calcium-handling stage only: TDD reaches that stage through a metabolic route, not through an inherited ion-channel variant, so the module's trigger node is deliberately not claimed.

cardiomyocyte CL:0000746

cardiac muscle cell action potential GO:0086001 ⚠ ABNORMAL

Downstream

Arrhythmogenic Substrate and Triggered Activity Prolonged, heterogeneous repolarization across the ventricular wall creates the substrate for triggered beats and reentry.

Show evidence (3 references)

PMID:42389941 SUPPORT In Vitro

"During the crisis, TANGO2-/- hiPSC-CMs exhibited AP prolongation, prevented by intracellular delivery of Mg-ATP or creatine kinase."

Establishes that action-potential prolongation is directly caused by the cardiomyocyte energy deficit.

PMID:42389941 SUPPORT In Vitro

"Importantly, the metabolic crisis upregulated TRPM4, an ATP- and Ca-regulated channel. TRPM4 siRNA knockdown or pharmacological block prevented AP prolongation without rescuing the energetic deficit of TANGO2-/- hiPSC-CMs."

Identifies TRPM4 as the effector channel translating ATP deficiency into repolarization abnormality.

PMID:42389941 SUPPORT In Vitro

"LTCC inhibition with verapamil prevented AP prolongation by normalizing ATP/ADP ratios and intracellular Ca mishandling."

Documents disturbed intracellular calcium handling and its pharmacological correction.

Arrhythmogenic Substrate and Triggered Activity

At the tissue level the cellular repolarization defect appears as marked QTc prolongation, which is present in essentially every documented TDD cardiac crisis (median QTc 547 ms in a 27-patient multicentre series), and in a minority as a type I Brugada pattern. The resulting dispersion of repolarization is the substrate on which triggered beats initiate ventricular arrhythmia.

cardiomyocyte CL:0000746

cardiac conduction GO:0061337 ↕ DYSREGULATED

heart UBERON:0000948

Downstream

Ventricular Tachyarrhythmia and Cardiac Arrest Triggered beats on a dispersed-repolarization substrate degenerate into ventricular tachycardia, torsade de pointes and cardiac arrest.

Show evidence (2 references)

PMID:35568137 SUPPORT Human Clinical

"During crisis, QTc prolongation occurred in all (median 547 ms; IQR 504-600 ms) and a type I Brugada pattern in 8 (26%)."

Quantifies universal QTc prolongation within cardiac crises, with the median value and the Brugada-pattern minority.

PMID:42389941 SUPPORT In Vitro

"These findings suggest a mechanistic link between ATP deficiency, TRPM4 activation, and AP prolongation in TDD."

Supplies the mechanistic chain connecting the cellular node to this tissue-level substrate.

Ventricular Tachyarrhythmia and Cardiac Arrest

Ventricular tachycardia occurred in 78% and cardiac arrest in 74% of patients admitted with a TDD cardiac crisis, with cardiomyopathy in 70% and 37% mortality, six of ten deaths arrhythmia-related. These arrhythmias are recalcitrant to standard antiarrhythmic drugs and constitute the leading cause of death in the disorder, which is why they are modelled as the terminal node of the cardiac arm.

heart UBERON:0000948

Show evidence (2 references)

PMID:35568137 SUPPORT Human Clinical

"Arrhythmias included VT in 21 (78%), supraventricular tachycardia in 3 (11%), and heart block in 1 (4%). Nineteen patients (70%) developed cardiomyopathy, and 20 (74%) experienced a cardiac arrest. There were 10 deaths (37%), 6 related to arrhythmias."

The primary quantitative outcome data for the cardiac arm within crisis admissions.

PMID:38855866 SUPPORT Other

"TDD-associated cardiac arrhythmias are recalcitrant to standard antiarrhythmic medications and constitute the leading cause of death."

Establishes arrhythmia as the leading cause of death and its refractoriness to conventional therapy. Evidence source is OTHER because this is the framing statement of an iPSC-cardiomyocyte study rather than its own clinical result; the mortality figures themselves are cited from PMID:35568137 elsewhere in this entry.

Oligodendroglial Lipid Dysregulation and Cerebellar Myelin Loss

Constitutive and oligodendrocyte-specific Tango2 knockout mice both reproduce the motor deficits seen in TDD, with robust cerebellar myelin loss, increased cerebellar synapse number, and downregulation of phospholipid-metabolism programmes. Vitamin B5 supplementation alleviates both the motor deficit and the myelin defect. This provides a cell-autonomous, non-crisis route from TANGO2 loss to the chronic ataxia and motor phenotype; it is a mouse finding not yet confirmed in human tissue.

oligodendrocyte CL:0000128

phospholipid biosynthetic process GO:0008654 ↓ DECREASED

cerebellum UBERON:0002037

Downstream

Progressive Neurodegeneration and Regression Cerebellar myelin loss contributes to the chronic ataxia, dysarthria and motor decline independently of acute crises.

Show evidence (2 references)

PMID:42522778 SUPPORT Model Organism

"Behavioral analyses revealed that both constitutive and oligodendrocyte-specific deletion of Tango2 recapitulate the motor deficits associated with individuals with TDD."

Shows the motor phenotype is attributable to oligodendroglial TANGO2 loss specifically.

PMID:42522778 SUPPORT Model Organism

"Morphological quantifications further showed that Tango2 deletion led to robust cerebellar myelin loss and an increase in synapse number in the cerebellar cortex."

Provides the structural cerebellar correlate of the motor deficit.

Progressive Neurodegeneration and Regression

Over the course of the disease, individuals develop global brain atrophy with cognitive impairment and pyramidal signs. Neuroimaging shows variable cerebral and white-matter atrophy and ventriculomegaly. Post-mortem examination in one case revealed heterotopic neurons in the cerebral white matter, raising the possibility of an additional neuronal-migration contribution to the neurodevelopmental phenotype.

neuron CL:0000540

brain UBERON:0000955

Show evidence (2 references)

PMID:26805782 SUPPORT Human Clinical

"Over the course of the disease, all individuals developed global brain atrophy with cognitive impairment and pyramidal signs."

Documents the progressive neurodegenerative trajectory in the index cohort.

PMID:31276219 SUPPORT Human Clinical

"In one deceased patient, post-mortem autopsy revealed heterotopic neurons in the cerebral white matter, indicating a possible role for TANGO2 in neuronal migration."

A single autopsy observation; recorded as PARTIAL because a neuronal-migration role is explicitly framed by the authors as a possibility, not an established mechanism.

⬡

Pathograph

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

●

Phenotypes

26

Cardiovascular 4

QT Prolongation Prolonged QT interval HP:0001657

Temporal: ACUTE

Show evidence (1 reference)

PMID:35568137 SUPPORT Human Clinical

"During crisis, QTc prolongation occurred in all (median 547 ms; IQR 504-600 ms) and a type I Brugada pattern in 8 (26%)."

Quantifies universal QTc prolongation and the median value within crisis admissions.

Ventricular Tachycardia HP:0004756

Temporal: ACUTE

Show evidence (2 references)

PMID:35568137 SUPPORT Human Clinical

"Arrhythmias included VT in 21 (78%), supraventricular tachycardia in 3 (11%), and heart block in 1 (4%)."

Gives the ventricular tachycardia proportion within cardiac-crisis admissions.

PMID:38855866 SUPPORT Other

"TDD-associated cardiac arrhythmias are recalcitrant to standard antiarrhythmic medications and constitute the leading cause of death."

Establishes drug refractoriness and mortality significance. Evidence source is OTHER because this is the framing statement of an iPSC-cardiomyocyte study rather than its own clinical result.

Cardiac Arrest HP:0001695

Temporal: ACUTE

Show evidence (1 reference)

PMID:35568137 SUPPORT Human Clinical

"Nineteen patients (70%) developed cardiomyopathy, and 20 (74%) experienced a cardiac arrest. There were 10 deaths (37%), 6 related to arrhythmias."

Quantifies cardiac arrest and arrhythmia-attributable mortality within crisis admissions.

Cardiomyopathy HP:0001638

Temporal: ACUTE

Show evidence (1 reference)

PMID:35568137 SUPPORT Human Clinical

"Nineteen patients (70%) developed cardiomyopathy, and 20 (74%) experienced a cardiac arrest."

Quantifies crisis-associated cardiomyopathy.

Digestive 1

Feeding Difficulties HP:0011968

Temporal: CHRONIC

Show evidence (1 reference)

PMID:29369572 SUPPORT Other

"feeding therapy and/or gastrostomy tube feeding as needed"

Recorded as PARTIAL because this is a management recommendation implying feeding difficulty rather than a direct report of the phenotype or its frequency. Evidence source is OTHER because this is a GeneReviews chapter.

Endocrine 1

Hypothyroidism FREQUENT HP:0000821

Temporal: CHRONIC

Show evidence (1 reference)

PMID:32929747 SUPPORT Human Clinical

"Here, we describe a cohort of 20 French patients bearing mutations in the TANGO2 gene. We found that the main clinical presentation was the association of neurodevelopmental delay (n = 17), acute metabolic crises (n = 17) and hypothyroidism (n = 12), with a large intrafamilial clinical variability."

Gives numerator and denominator (12/20 = 60%), which falls in the FREQUENT band (79-30%).

Genitourinary 1

Myoglobinuria HP:0002913

Temporal: ACUTE

Show evidence (1 reference)

PMID:39665114 SUPPORT Human Clinical

"The patient's clinical course was marked by rhabdomyolysis-induced muscle pain, weakness and dark urine."

Case-report documentation of myoglobinuric dark urine during a crisis.

Metabolism 3

Hypoglycemia HP:0001943

Temporal: ACUTE

Show evidence (1 reference)

PMID:31339582 SUPPORT Human Clinical

"a distinct clinical and biochemical phenotype of recurrent metabolic crises, hypoglycemia, lactic acidosis, rhabdomyolysis, arrhythmias, and encephalopathy with cognitive decline"

Places hypoglycaemia within the recognized biochemical crisis phenotype.

Lactic Acidosis HP:0003128

Temporal: ACUTE

Show evidence (2 references)

PMID:32909282 SUPPORT Other

"recurrent crisis-induced rhabdomyolysis, encephalopathy, seizures, lactic acidosis, hypoglycemia, and cardiac arrhythmias"

Names lactic acidosis as a crisis component. Evidence source is OTHER because this is the background statement of an in vitro study.

PMID:31339582 SUPPORT Human Clinical

"a distinct clinical and biochemical phenotype of recurrent metabolic crises, hypoglycemia, lactic acidosis, rhabdomyolysis, arrhythmias, and encephalopathy with cognitive decline"

Primary clinical-series support for lactic acidosis as a crisis finding.

Elevated Creatine Kinase Elevated circulating creatine kinase concentration HP:0003236

Temporal: ACUTE

Show evidence (1 reference)

PMID:34668327 SUPPORT Human Clinical

"Findings such as elevated creatine kinase, hypothyroidism, ketotic hypoglycemia, QT prolongation, or abnormalities of long-chain acylcarnitines and urine dicarboxylic acids should raise clinical suspicion for this life-threatening condition."

Establishes elevated CK as a diagnostic red flag for TDD.

Musculoskeletal 4

Spasticity HP:0001257

Show evidence (2 references)

PMID:31276219 SUPPORT Human Clinical

"All patients showed developmental delay with ataxia, dysarthria, intellectual disability, or signs of spastic diplegia."

Names spastic diplegia among the chronic neurological findings of the cohort.

PMID:26805782 SUPPORT Human Clinical

"all individuals developed global brain atrophy with cognitive impairment and pyramidal signs"

Independent documentation of pyramidal signs in the index cohort.

Hypotonia HP:0001252

Show evidence (1 reference)

PMID:29369572 SUPPORT Other

"including sudden onset of hypotonia, ataxia with loss of balance, head and body tilt, increased dysarthria, drooling, lethargy, and disorientation"

Names hypotonia within the spell phenotype. Evidence source is OTHER because this is a GeneReviews chapter.

Rhabdomyolysis FREQUENT HP:0003201

Temporal: RECURRENT

Show evidence (2 references)

PMID:34668327 SUPPORT Human Clinical

"Common clinical features seen in >70% of all individuals include acute metabolic crisis, rhabdomyolysis, neurologic abnormalities, developmental delay, and intellectual disability."

Pooled review of 92 individuals giving a lower bound above 70%, consistent with the FREQUENT band (79-30%). The band is set from this whole-cohort figure rather than from the 15/17 crisis-conditional proportion.

PMID:32929747 SUPPORT Human Clinical

"Metabolic crises included rhabdomyolysis (15/17), neurological symptoms (14/17), and cardiac features (12/17; long QT (n = 10), Brugada pattern (n = 2), cardiac arrhythmia (n = 6)) that required intensive care."

Gives the crisis-conditional proportion (15 of 17 patients who had crises). Quoted for the composition of a crisis, not as the whole-cohort frequency band.

Muscle Weakness HP:0001324

Show evidence (1 reference)

PMID:37119590 SUPPORT Human Clinical

"We report a 40-year-old woman affected by limb-girdle weakness and mild intellectual disability caused by the recurrent deletion of exons 3-9 in homozygosity in the TANGO2 gene."

Documents chronic limb-girdle weakness at the mild end of the phenotypic spectrum.

Nervous System 11

Global Developmental Delay VERY_FREQUENT HP:0001263

Course: PROGRESSIVE

Show evidence (2 references)

PMID:32929747 SUPPORT Human Clinical

"Here, we describe a cohort of 20 French patients bearing mutations in the TANGO2 gene. We found that the main clinical presentation was the association of neurodevelopmental delay (n = 17), acute metabolic crises (n = 17) and hypothyroidism (n = 12), with a large intrafamilial clinical variability."

Gives both numerator and denominator (17/20 = 85%), which falls in the VERY_FREQUENT band (99-80%).

PMID:31276219 SUPPORT Human Clinical

"All patients showed developmental delay with ataxia, dysarthria, intellectual disability, or signs of spastic diplegia."

Independent series confirming universal developmental delay in its cohort.

Intellectual Disability FREQUENT HP:0001249

Show evidence (1 reference)

PMID:34668327 SUPPORT Human Clinical

"Common clinical features seen in >70% of all individuals include acute metabolic crisis, rhabdomyolysis, neurologic abnormalities, developmental delay, and intellectual disability."

A pooled review of 92 individuals reporting intellectual disability in more than 70%. The stated floor is consistent with the FREQUENT band (79-30%); the band is assigned conservatively because the source gives only a lower bound.

Ataxia HP:0001251

Course: PROGRESSIVE

Show evidence (2 references)

PMID:36473599 SUPPORT Human Clinical

"Symptoms included ataxia, dystonia, and speech difficulties, typically starting between the ages of 1 to 3 years."

Establishes ataxia and its typical age of onset in the 73-patient natural-history cohort.

PMID:31276219 SUPPORT Human Clinical

"All patients showed developmental delay with ataxia, dysarthria, intellectual disability, or signs of spastic diplegia."

Independent series naming ataxia as a core neurological feature.

Dysarthria HP:0001260

Show evidence (2 references)

PMID:31276219 SUPPORT Human Clinical

"All patients showed developmental delay with ataxia, dysarthria, intellectual disability, or signs of spastic diplegia."

Names dysarthria among the core chronic neurological features.

PMID:29369572 SUPPORT Other

"including sudden onset of hypotonia, ataxia with loss of balance, head and body tilt, increased dysarthria, drooling, lethargy, and disorientation"

Documents acute worsening of dysarthria during spells. Evidence source is OTHER because this is a GeneReviews expert-consensus chapter.

TANGO2 Spells Episodic ataxia HP:0002131

Temporal: RECURRENT

Show evidence (1 reference)

PMID:29369572 SUPPORT Other

"Most individuals have TANGO2 spells, non-life-threatening paroxysmal worsening of baseline symptoms, including sudden onset of hypotonia, ataxia with loss of balance, head and body tilt, increased dysarthria, drooling, lethargy, and disorientation."

Defines the spell phenotype and its distinction from metabolic crises. Evidence source is OTHER because this is a GeneReviews chapter.

Seizures HP:0001250

Show evidence (2 references)

PMID:29369572 SUPPORT Other

"TANGO2 deficiency is characterized by developmental delay, intellectual disability, gait incoordination, speech difficulties, seizures, and hypothyroidism."

Places seizures among the core chronic features. Evidence source is OTHER because this is a GeneReviews chapter.

PMID:30245509 SUPPORT Human Clinical

"Primary features include metabolic crisis with rhabdomyolysis, encephalopathy, intellectual disability, seizures, and cardiac arrhythmias."

Independent case-series confirmation.

Developmental Regression HP:0002376

Show evidence (2 references)

PMID:36502486 SUPPORT Other

"Mutations in the Transport and Golgi Organization 2 (TANGO2) gene are associated with intellectual deficit, neurodevelopmental delay and regression."

Names regression explicitly as part of the TANGO2 phenotype. Evidence source is OTHER because this is the background statement of a Drosophila and human-cell study.

PMID:39641377 SUPPORT Human Clinical

"A 7-year-old Chinese girl presented with epilepsy, developmental delay, neuroregression, and episodes of dyskinesia."

Direct clinical documentation of neuroregression in an affected child.

Cerebral Atrophy HP:0002059

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:26805782 SUPPORT Human Clinical

"Over the course of the disease, all individuals developed global brain atrophy with cognitive impairment and pyramidal signs."

Directly documents progressive global brain atrophy.

Dystonia HP:0001332

Show evidence (1 reference)

PMID:36473599 SUPPORT Human Clinical

"Symptoms included ataxia, dystonia, and speech difficulties, typically starting between the ages of 1 to 3 years."

Names dystonia among the core early motor features of the natural-history cohort.

Delayed Speech and Language Development HP:0000750

Show evidence (2 references)

PMID:29369572 SUPPORT Other

"TANGO2 deficiency is characterized by developmental delay, intellectual disability, gait incoordination, speech difficulties, seizures, and hypothyroidism."

Lists speech difficulties among the core clinical characteristics. Evidence source is OTHER because this is a GeneReviews chapter.

PMID:36473599 SUPPORT Human Clinical

"Symptoms included ataxia, dystonia, and speech difficulties, typically starting between the ages of 1 to 3 years."

Places speech difficulty in the early-childhood onset window in the 73-patient cohort.

Acute Metabolic Crisis with Encephalopathy FREQUENT HP:0001298

Temporal: RECURRENT

Show evidence (2 references)

PMID:36473599 SUPPORT Human Clinical

"A total of 46/71 (65%) patients suffered metabolic crises, and of those, 30 (65%) developed cardiac crises."

Whole-cohort proportion of 65% (46/71) in the largest natural-history study, which falls in the FREQUENT band (79-30%).

PMID:29369572 SUPPORT Other

"life-threatening acute metabolic crises can occur, including rhabdomyolysis with elevated creatine phosphokinase and liver transaminases, hypoglycemia, prolonged QTc on EKG, ventricular arrhythmias, and/or cardiomyopathy"

Defines the composition of the crisis. Evidence source is OTHER because this is a GeneReviews chapter.

Other 1

Torsade de Pointes HP:0001664

Temporal: ACUTE

Show evidence (1 reference)

PMID:29369572 SUPPORT Other

"continuous rhythm monitoring for arrhythmias including premature ventricular contractions, ventricular tachycardia, and torsade de pointes"

Recorded as PARTIAL because this is a surveillance recommendation naming torsade de pointes as an arrhythmia to watch for, rather than a report of its observed frequency. Evidence source is OTHER because this is a GeneReviews chapter.

🧬

Genetic Associations

2

TANGO2 (Biallelic loss-of-function variants in TANGO2 at 22q11.21 are necessary and sufficient to cause TANGO2 deficiency disorder. Reported pathogenic classes include multiexon deletions, nonsense, frameshift, canonical splice-site, small in-frame deletion and missense variants. The recurrent 34-kb deletion of exons 3-9 is the single most common allele, seen in 42% of reported individuals and enriched in European-ancestry cases; c.460G>A (p.Gly154Arg) is recurrent in Hispanic/Latino families. Because the disorder is caused by deletions as often as by sequence variants, exon-level deletion/duplication analysis is required alongside sequencing, and hemizygous variants that appear heterozygous on sequencing alone are a recognized diagnostic pitfall.)

Gene: TANGO2 hgnc:25439 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (6 references)

PMID:26805782 SUPPORT Human Clinical

"Our results establish TANGO2 deficiency as a clinically recognizable cause of pediatric disease with multi-organ involvement."

The gene-disease relationship as first established.

PMID:34668327 SUPPORT Human Clinical

"Of the 27 pathogenic variants reported to date, the recurrent exons 3-9 deletion represents the most common variant seen in 42% of individuals with TANGO2 deficiency."

Quantifies the dominance of the recurrent exon 3-9 deletion in the reported allelic spectrum.

PMID:31339582 SUPPORT Human Clinical

"The other subjects carried three novel homozygous (c.262C>T/p.Arg88*; c.220A>C/p.Thr74Pro; c.380+1G>A), and two further novel heterozygous"

Illustrates the nonsense, missense and splice-site variant classes contributing to the allelic spectrum.

+ 3 more references

TANGO2 unmasked by a 22q11.2 deletion in trans (TANGO2 lies within the interval recurrently deleted in 22q11.2 deletion syndrome. An individual carrying a 22q11.2 deletion that removes one TANGO2 allele develops TDD if the remaining allele carries a pathogenic sequence variant - an autosomal-recessive second diagnosis unmasked by the deletion. This configuration has been documented directly, and it makes 22q11.2 deletion syndrome an at-risk group in which TDD is thought to be underdiagnosed because the phenotypes overlap. A multicentre screen of 435 individuals with 22q11.2 deletion syndrome identified 21 meeting consensus criteria for TANGO2 testing; of the nine actually sequenced with deletion/duplication analysis, none were diagnosed with TDD, so the practical yield of symptom-based screening remains unproven. This entry describes the TDD side of that relationship; the 22q11.2 Deletion Syndrome entry covers it as a second-diagnosis and differential-diagnosis consideration.)

Gene: TANGO2 hgnc:25439 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (5 references)

PMID:38829177 SUPPORT Human Clinical

"TANGO2 deficiency disorder (TDD) is a rare, autosomal recessive condition caused by pathogenic variants in TANGO2, a gene residing within the region commonly deleted in 22q11.2 deletion syndrome (22q11.2DS)."

Establishes that TANGO2 lies within the 22q11.2 deleted interval.

PMID:38829177 SUPPORT Human Clinical

"Although patients with 22q11.2DS are at substantially higher risk for comorbid TDD, it remains underdiagnosed within 22q11.2DS, likely due to overlapping symptomatology and a lack of knowledge about TDD."

Supports the elevated risk and the underdiagnosis concern in this group.

PMID:38829177 SUPPORT Human Clinical

"Of the nine patients undergoing TANGO2 sequencing with del/dup analysis, none were ultimately diagnosed with TDD."

Recorded as PARTIAL: the null yield constrains how strongly symptom-based screening can be recommended, while the study's own conclusion is that better prospective screening tools are needed rather than that screening is unwarranted.

+ 2 more references

💊

Medical Actions

10

Daily B-Complex or Multivitamin Supplementation

Action: nutritional supplementation Ontology label: Nutritional Support NCIT:C15433

Agent: pantothenate (vitamin B5) CHEBI:29032 folic acid (vitamin B9) CHEBI:27470

Daily supplementation with a multivitamin containing all eight B vitamins, or a B-complex preparation, is the principal disease-directed intervention and is recommended in expert-consensus guidance. The evidence base is convergent but not randomized: in the 73-patient natural-history study metabolic crises were significantly reduced after supplementation was started, and an independent natural-history analysis found that multivitamin/B-complex intake greatly diminished the risk of cardiac crises. Both observations are retrospective and uncontrolled. No randomized controlled trial has been performed, optimal dose and formulation are not standardized, and the long-term safety of sustained high-dose supplementation in children (including vitamin B6 toxicity, for which serum monitoring is advised) is explicitly flagged as unresolved. This is therefore curated as a promising, guideline-endorsed but trial-unvalidated intervention rather than as proven standard of care.

Mechanism Target:

RESTORES Lipid and Acyl-CoA Homeostasis Failure — Pantothenate is the biosynthetic precursor of coenzyme A; restoring the CoA precursor pool is the proposed route by which B5 reverses the acyl-CoA and lipid imbalance.

Target Phenotypes: Encephalopathy HP:0001298 Ventricular tachycardia HP:0004756

Show evidence (7 references)

PMID:29369572 SUPPORT Other

"Daily supplementation with a multivitamin including all eight B vitamins or a B-complex vitamin at the minimum recommended daily allowance for age."

The expert-consensus targeted-therapy recommendation. Evidence source is OTHER because this is a GeneReviews chapter, not a trial.

PMID:36473599 SUPPORT Human Clinical

"Metabolic crises were significantly decreased after the initiation of B-complex or multivitamin supplementation."

The primary observational human signal, from the 73-patient natural-history cohort.

PMID:36473599 SUPPORT Human Clinical

"We provide the most comprehensive review of natural history of TDD and important observational data suggesting that B-complex or multivitamins may prevent metabolic crises."

Recorded as PARTIAL because the authors frame their own result as observational and hedged ("suggesting", "may prevent"), which is the epistemic level at which this treatment should be curated.

+ 4 more references

Vitamin B5 (Pantothenate)

Action: nutritional supplementation Ontology label: Nutritional Support NCIT:C15433

Agent: pantothenate (vitamin B5) CHEBI:29032

Pantothenate, the coenzyme A precursor, is the best-characterized single active component of B-complex therapy in model systems. It improves multiple TANGO2 loss-of-function defects in Drosophila, rescues membrane-trafficking defects in human cells, reverses the lipid-profile abnormalities of TANGO2-deficient human cells and flies, and alleviates motor deficits and cerebellar myelin loss in Tango2 knockout mice. Human evidence is limited to single-patient reports of symptomatic improvement on B5 monotherapy; it is not established as a standalone therapy.

Mechanism Target:

RESTORES Lipid and Acyl-CoA Homeostasis Failure — Restores the coenzyme A precursor pool needed for acyl-CoA-dependent lipid acylation.

Show evidence (5 references)

PMID:36502486 SUPPORT Model Organism

"We demonstrate that vitamin B5 specifically improves multiple defects associated with TANGO2 loss-of-function in Drosophila"

The primary in vivo rescue result in the Drosophila model.

PMID:36502486 SUPPORT In Vitro

"and rescues membrane trafficking defects in human cells"

The parallel rescue of the ER-to-Golgi trafficking defect in human TANGO2-deficient cells.

PMID:36502486 SUPPORT Model Organism

"Our data suggest that a B complex supplement containing vitamin B5/pantothenate may have therapeutic benefits in individuals with TANGO2-deficiency disease."

Recorded as PARTIAL because the translational claim is the authors' hedged extrapolation from model systems, not a human result.

+ 2 more references

Folate (Vitamin B9) for Arrhythmia Prevention

Action: nutritional supplementation Ontology label: Nutritional Support NCIT:C15433

Agent: folic acid (vitamin B9) CHEBI:27470

High-dose folate virtually abolishes arrhythmias in patient-derived TANGO2-null iPSC cardiomyocytes, and the effect is blocked by methotrexate, indicating a requirement for intracellular folate metabolism. Combined B5 plus B9 pretreatment prevents the palmitate-and-fasting-induced energetic crisis in an independent CRISPR cardiomyocyte model. Human evidence is observational only; folate is not established as a standalone antiarrhythmic in TDD and is delivered in practice as part of B-complex supplementation.

Mechanism Target:

INHIBITS Cardiomyocyte ATP Depletion and Repolarization Instability — Prevents the energy-dependent action-potential prolongation that underlies TDD arrhythmia.

Target Phenotypes: Ventricular tachycardia HP:0004756

Show evidence (2 references)

PMID:38855866 SUPPORT In Vitro

"we demonstrated that high-dose folate (vitamin B9) virtually abolishes arrhythmias in TDD iPSC-CMs and that folate's effect was blocked by the dihydrofolate reductase inhibitor methotrexate, supporting the need for intracellular folate to mediate antiarrhythmic effects"

The primary in vitro antiarrhythmic result and its mechanistic control.

PMID:42389941 SUPPORT In Vitro

"This crisis was prevented by 2-week treatment with vitamins B5 and B9."

Independent CRISPR cardiomyocyte model showing combined B5/B9 pretreatment prevents the energetic crisis.

Acute Crisis Management with Dextrose-Containing Fluids and Nutrition

Action: fluid replacement therapy Ontology label: Hydration Therapy NCIT:C66896

Agent: glucose CHEBI:17234

During an acute crisis, admission for intravenous hydration with glucose-containing fluids, correction of hypoglycaemia, and prompt restoration of full enteral or parenteral nutrition including vitamin supplementation is the mainstay. Fluid rate must be adjusted against echocardiographic assessment of cardiac function to avoid pulmonary oedema. Glucose alone appears insufficient: initiation of feeds was associated with a reduction in ventricular tachycardia events, suggesting complete nutrition rather than dextrose alone is what matters.

Mechanism Target:

INHIBITS Catabolic-Stress Metabolic Decompensation — Reverses the catabolic state driving the crisis by restoring exogenous fuel supply.

Show evidence (2 references)

PMID:29369572 SUPPORT Other

"intravenous (IV) hydration with glucose-containing fluids for hypoglycemia; echocardiogram to assess cardiac function with adjustment of IV fluids to prevent pulmonary edema"

The consensus acute-management protocol including the fluid-titration caveat. Evidence source is OTHER because this is a GeneReviews chapter.

PMID:35568137 SUPPORT Human Clinical

"Initiation of feeds seemed to decrease VT events."

Recorded as PARTIAL because this is a hedged retrospective observation ("seemed to") rather than a controlled comparison.

Acute Antiarrhythmic Management

Action: Pharmacotherapy NCIT:C15986

Agent: magnesium sulfate CHEBI:32599 isoproterenol CHEBI:64317 verapamil CHEBI:9948

TDD crisis arrhythmias respond poorly to standard antiarrhythmic drugs. Reported effective measures are intravenous magnesium (with magnesium maintained above 2.2 mg/dL), isoproterenol, atrial overdrive pacing, and aggressive electrolyte correction; verapamil was effective in one patient and has independent mechanistic support from L-type calcium channel inhibition in the cardiomyocyte model. Management by an electrophysiologist is recommended rather than application of generic long-QT algorithms.

Mechanism Target:

INHIBITS Arrhythmogenic Substrate and Triggered Activity — Magnesium, rate support and calcium-channel blockade act to suppress triggered activity on the prolonged-repolarization substrate.

Target Phenotypes: Ventricular tachycardia HP:0004756

Show evidence (4 references)

PMID:35568137 SUPPORT Human Clinical

"Among 10 patients who survived VT without ECMO, successful treatment included intravenous magnesium, isoproterenol, and atrial pacing in multiple cases and verapamil in 1 patient."

The primary clinical evidence for the specific agents used successfully during TDD arrhythmia.

PMID:29369572 SUPPORT Other

"supplemental magnesium to maintain magnesium >2.2 mg/dL to minimize arrhythmias"

Sources the specific magnesium target stated in this treatment. Evidence source is OTHER because this is a GeneReviews chapter.

PMID:29369572 SUPPORT Other

"Due to the recalcitrant nature of ventricular arrhythmias, management by an electrophysiologist is recommended."

Supports specialist-directed management. Evidence source is OTHER because this is a GeneReviews chapter.

+ 1 more reference

Extracorporeal Membrane Oxygenation for Refractory Arrhythmia

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

ECMO is used as a last-resort rescue for arrhythmia or cardiogenic shock refractory to medical therapy. In the 27-patient cardiac-crisis series, arrhythmias were controlled after ECMO in 6 patients, 5 of whom survived. In a single reported case, thoracoscopic left sympathectomy performed during ECMO support terminated a refractory ventricular fibrillation storm.

Target Phenotypes: Cardiac arrest HP:0001695

Show evidence (2 references)

PMID:35568137 SUPPORT Human Clinical

"In 6 patients, arrhythmias were controlled after extracorporeal membrane oxygenation (ECMO) support; 5 of these patients survived."

Quantifies ECMO outcomes in refractory TDD arrhythmia.

PMID:39665114 SUPPORT Human Clinical

"In a life-saving therapeutic approach, the patient underwent a thoracoscopic left sympathectomy during extracorporeal membrane oxygenation (ECMO) support. Remarkably, this intervention resulted in the termination of the ventricular arrhythmia storm."

Recorded as PARTIAL because sympathectomy during ECMO is described in a single case report and is not an established TDD intervention.

Avoidance of Catabolic Triggers and Sick-Day Planning

Action: dietary intervention Ontology label: Dietary Intervention NCIT:C15447

Preventive care centres on avoiding prolonged fasting and dehydration, maintaining regular meals, avoiding a ketogenic diet, limiting exertion and heat exposure during illness, and having a written sick-day plan with early hospital evaluation for fever, reduced intake, weakness, dark urine, seizure or palpitations.

Mechanism Target:

INHIBITS Catabolic Stress Exposure — Removes or blunts the extrinsic trigger required to convert the latent genotype into an acute crisis.

Show evidence (1 reference)

PMID:29369572 SUPPORT Other

"Agents/circumstances to avoid: Triggers for TANGO2 spells and acute metabolic crises including fasting, dehydration, overexertion, exposure to excessive heat, ketogenic diet, and infections."

The consensus avoidance recommendation. Evidence source is OTHER because this is a GeneReviews chapter.

Levothyroxine for Hypothyroidism

Action: Pharmacotherapy NCIT:C15986

Agent: levothyroxine CHEBI:18332

Hypothyroidism is common and treatable; levothyroxine is given as needed, with annual TSH and free T4 surveillance.

Target Phenotypes: Hypothyroidism HP:0000821

Show evidence (1 reference)

PMID:29369572 SUPPORT Other

"levothyroxine as needed for hypothyroidism"

The consensus treatment for the endocrine manifestation. Evidence source is OTHER because this is a GeneReviews chapter.

Cardiac Surveillance

Action: electrocardiography Ontology label: Electrocardiography NCIT:C38053

Serial ECG for QTc and for emergence of a type 1 Brugada pattern, continuous rhythm monitoring during illness, and echocardiography at a frequency guided by the individual's history of metabolic and cardiac crises.

Target Phenotypes: Prolonged QT interval HP:0001657

Show evidence (1 reference)

PMID:29369572 SUPPORT Other

"EKG to monitor QTc and for development of type 1 Brugada pattern; continuous rhythm monitoring for arrhythmias including premature ventricular contractions, ventricular tachycardia, and torsade de pointes"

The consensus cardiac surveillance protocol. Evidence source is OTHER because this is a GeneReviews chapter.

Genetic Counseling

Action: genetic counseling Ontology label: Genetic Counseling NCIT:C15240

Counselling should cover autosomal-recessive recurrence risk (25% per pregnancy when both parents are carriers), marked variable expressivity that limits genotype-based prognosis, the requirement to test for deletions as well as sequence variants, the availability of carrier, prenatal and preimplantation testing once the familial variants are known, and cascade testing of apparently asymptomatic siblings so that B-complex vitamins, supportive treatment and trigger avoidance can be started before a first crisis.

Show evidence (4 references)

PMID:29369572 SUPPORT Other

"If both parents are known to be heterozygous for a TANGO2 pathogenic variant, each sib of an affected individual has at conception a 25% chance of being affected, a 50% chance of being a carrier, and a 25% chance of inheriting neither of the familial pathogenic variants."

Sources the autosomal-recessive recurrence-risk counselling content. Evidence source is OTHER because this is a GeneReviews chapter.

PMID:29369572 SUPPORT Other

"Once the TANGO2 pathogenic variants have been identified in an affected family member, carrier testing for at-risk relatives and prenatal/preimplantation genetic testing are possible."

Sources the carrier-testing, prenatal and preimplantation testing options. Evidence source is OTHER because this is a GeneReviews chapter.

PMID:29369572 SUPPORT Other

"It is appropriate to clarify the genetic status of apparently asymptomatic older and younger sibs of an affected individual by molecular genetic testing to allow prompt initiation of B-complex vitamins, supportive treatment, and avoidance of triggers for TANGO2 spells and acute metabolic crises."

Sources cascade testing of at-risk siblings and the actionable reason for it. Evidence source is OTHER because this is a GeneReviews chapter.

+ 1 more reference

🌍

Environmental Factors

2

Catabolic stress

Fever and intercurrent illness, fasting, dehydration, reduced oral intake, excessive heat, overexertion and a ketogenic diet precipitate metabolic crises and TANGO2 spells. These are not causes of the disorder but the modifiable determinants of when and how severely it manifests, which is why avoidance of catabolism is the backbone of preventive care.

Show evidence (1 reference)

PMID:29369572 SUPPORT Other

"Triggers for TANGO2 spells and acute metabolic crises including fasting, dehydration, overexertion, exposure to excessive heat, ketogenic diet, and infections."

Enumerates the crisis triggers. Evidence source is OTHER because this is a GeneReviews chapter.

Mechanism Target:

TRIGGERS Catabolic Stress Exposure — The node is named for this exposure and describes the disorder as stress-unmasked: the genotype is present from conception and the acute phenotype requires an extrinsic catabolic challenge. Exposure and node are therefore the same thing, and the cited chapter enumerates the precipitants the node lists.

Show evidence (1 reference)

PMID:29369572 SUPPORT Other

"Triggers for TANGO2 spells and acute metabolic crises including fasting, dehydration, overexertion, exposure to excessive heat, ketogenic diet, and infections."

Enumerates fasting, dehydration, overexertion, excessive heat, ketogenic diet and infection as triggers, which is this node's own content.

Anaesthetic exposure

Certain anaesthetic agents were identified as previously uncharacterized triggers of metabolic crises in a 20-patient cohort. This warrants multidisciplinary perioperative planning involving metabolic, anaesthetic and cardiology teams rather than a blanket contraindication, since the specific agents and mechanism are not established.

Show evidence (1 reference)

PMID:32929747 SUPPORT Human Clinical

"We show previously uncharacterized triggers of metabolic crises in TANGO2 patients, such as some anesthetics and possibly l-carnitine."

Recorded as PARTIAL because the authors themselves hedge the finding ("possibly") and do not identify the responsible agents or mechanism.

Mechanism Target:

TRIGGERS Catabolic-Stress Metabolic Decompensation — Pointed at the crisis rather than at the catabolic stress node, because an anaesthetic is not obviously a catabolic challenge and the node upstream is defined by catabolism; that is a real gap in the graph and is better stated than papered over. Graded partial throughout because the authors hedge the finding themselves and identify neither the responsible agents nor a mechanism, which is also why the practical recommendation is perioperative planning rather than a blanket contraindication.

Show evidence (1 reference)

PMID:32929747 SUPPORT Human Clinical

"We show previously uncharacterized triggers of metabolic crises in TANGO2 patients, such as some anesthetics and possibly l-carnitine."

Reports previously uncharacterised triggers of metabolic crises including some anaesthetics. The crisis is this node, but the sentence names no agent and offers no route to it.

🔬

Diagnosis

2

Molecular genetic testing with deletion/duplication analysis

Diagnosis is established by identifying biallelic pathogenic TANGO2 variants. Because multiexon deletions account for a large share of pathogenic alleles, testing must combine sequence analysis with exon-level deletion/duplication analysis; exome sequencing alone requires additional copy-number analysis. In an individual with a 22q11.2 deletion and suggestive features, the remaining TANGO2 allele should be sequenced.

genetic testing NCIT:C15709

Show evidence (2 references)

PMID:29369572 SUPPORT Other

"The diagnosis of TANGO2 deficiency is established in a proband with biallelic pathogenic variants in TANGO2 identified by molecular genetic testing."

States the diagnostic standard. Evidence source is OTHER because this is a GeneReviews chapter.

PMID:30245509 SUPPORT Human Clinical

"We illustrate the utility of routine ES data reanalysis whereby discovery of novel disease genes can lead to a diagnosis in previously unsolved cases and the need for additional copy-number variation analysis when ES is performed."

Supports the requirement for copy-number analysis alongside exome sequencing.

Crisis laboratory and cardiac evaluation

During illness or crisis, obtain serial creatine kinase, glucose, blood gas and lactate, electrolytes including magnesium, transaminases, renal function and urine myoglobin, together with continuous ECG/telemetry with repeated QTc assessment and echocardiography. Normal interictal acylcarnitines, lactate, carnitine or respiratory-chain studies do not exclude the diagnosis.

Show evidence (3 references)

PMID:34668327 SUPPORT Human Clinical

"Findings such as elevated creatine kinase, hypothyroidism, ketotic hypoglycemia, QT prolongation, or abnormalities of long-chain acylcarnitines and urine dicarboxylic acids should raise clinical suspicion for this life-threatening condition."

Lists the laboratory findings that should trigger evaluation for TDD.

PMID:32929747 SUPPORT Human Clinical

"Unexpectedly, plasma acylcarnitines, plasma FGF-21, muscle histology, and mitochondrial spectrometry were mostly normal."

Supports the caution that standard metabolic workup is frequently normal and cannot exclude TDD.

PMID:29369572 SUPPORT Other

"monitor creatine phosphokinase; EKG to monitor QTc and for development of type 1 Brugada pattern; continuous rhythm monitoring for arrhythmias including premature ventricular contractions, ventricular tachycardia, and torsade de pointes"

Sources the creatine kinase, serial QTc and continuous rhythm-monitoring elements of the crisis evaluation panel. Evidence source is OTHER because this is a GeneReviews chapter.

📈

Progression

4

Early infancy - apparently normal development

Age: birth to about 1 year

Development is typically normal in early infancy. The biallelic genotype is present from conception but produces no overt phenotype until milestones begin to lag.

Show evidence (1 reference)

PMID:36473599 SUPPORT Human Clinical

"Patients showed normal development in early infancy, with progressive delay in developmental milestones thereafter."

Establishes the normal early-infancy period preceding progressive milestone delay.

Baseline neurodevelopmental phenotype

Age: about 1 to 3 years onward

Progressive milestone delay emerges, with ataxia, dystonia and speech difficulties typically starting between 1 and 3 years, evolving into intellectual disability, dysarthria and paroxysmal TANGO2 spells.

Show evidence (1 reference)

PMID:36473599 SUPPORT Human Clinical

"Symptoms included ataxia, dystonia, and speech difficulties, typically starting between the ages of 1 to 3 years."

Fixes the age window in which the chronic neurological phenotype becomes manifest.

Episodic metabolic and cardiac crises

Age: childhood onward, median age 6.4 years at cardiac crisis admission

Superimposed on the chronic phenotype, catabolic stress precipitates metabolic crises with rhabdomyolysis and encephalopathy; about two-thirds of those who experience a metabolic crisis go on to have a cardiac crisis with QT prolongation and ventricular arrhythmia (30 of 71 individuals, 42%, in the natural-history cohort). Crisis manifestations including cardiomyopathy are often reversible, but each crisis carries a risk of sudden death.

Show evidence (2 references)

PMID:36473599 SUPPORT Human Clinical

"A total of 46/71 (65%) patients suffered metabolic crises, and of those, 30 (65%) developed cardiac crises."

Quantifies the proportion progressing from metabolic to cardiac crisis.

PMID:35568137 SUPPORT Human Clinical

"Twenty-seven children were admitted for 43 cardiac crises (median age 6.4 years"

Gives the median age at cardiac crisis admission.

Long-term course and severity spectrum

Age: lifelong

The course is lifelong. Developmental disability generally persists and may step down after severe crises, while global brain atrophy accrues. Severity ranges from a fatal early-onset crisis to an adult limb-girdle myopathy phenotype, and a minority never experience an overt crisis; intrafamilial variability is marked even between siblings sharing a genotype, so genotype does not predict trajectory.

Show evidence (3 references)

PMID:42196371 SUPPORT Human Clinical

"Clinical severity ranged from an asymptomatic individual under preventive therapy to a fatal early-onset metabolic crisis. Marked intrafamilial variability was observed in two siblings sharing the same genotype."

Documents the breadth of the severity spectrum and intrafamilial variability.

PMID:31276219 SUPPORT Human Clinical

"Of importance, we identify two subjects (aged 12 and 17 years) who have never experienced any overt episode of the catabolism-induced metabolic crises typical for the disease."

Shows that crises are not obligate and that a crisis-free course into adolescence is possible.

PMID:26805782 SUPPORT Human Clinical

"Over the course of the disease, all individuals developed global brain atrophy with cognitive impairment and pyramidal signs."

Documents the cumulative neurodegenerative component of the long-term course.

📊

Prevalence

2

Worldwide

Point Prevalence 0.1 per 100,000 1–9 per 1,000,000

An expert-review extrapolation of roughly 8,000 affected individuals worldwide, corresponding to about 1 per million. This is not a registry-derived estimate; TDD is widely regarded as substantially underdiagnosed, particularly within 22q11.2 deletion syndrome.

Show evidence (1 reference)

PMID:38836374 SUPPORT Other

"TANGO2 deficiency disease (TDD) is a rare genetic disorder estimated to affect ∼8000 individuals worldwide."

Supports the order-of-magnitude worldwide burden but is an estimate stated in a Perspective article rather than a measured population prevalence, hence PARTIAL.

Worldwide

Cases In Literature Ultra Rare

The largest single natural-history cohort assembled to date comprised 73 patients from 57 unrelated families across 16 countries.

Show evidence (1 reference)

PMID:36473599 SUPPORT Human Clinical

"Data were collected from 73 patients (59% male) from 57 unrelated families living in 16 different countries."

Quantifies the size of the largest reported TDD cohort.

🔀

Differential Diagnoses

4

Conditions with similar clinical presentations that must be differentiated from TANGO2 Deficiency Disorder:

22q11.2 deletion syndrome MONDO:0018923

Overlapping Features A 22q11.2 deletion is both a differential diagnosis and a risk state: TANGO2 lies inside the deleted interval, so an individual with 22q11.2 deletion syndrome who develops rhabdomyolysis, metabolic crises or ventricular arrhythmia should be evaluated for a pathogenic variant on the remaining TANGO2 allele rather than having those features attributed to the deletion syndrome alone.

Show evidence (1 reference)

PMID:38829177 SUPPORT Human Clinical

"Although patients with 22q11.2DS are at substantially higher risk for comorbid TDD, it remains underdiagnosed within 22q11.2DS, likely due to overlapping symptomatology and a lack of knowledge about TDD."

Supports both the phenotypic overlap and the recommendation to look for comorbid TDD.

Fatty acid oxidation disorders

Overlapping Features Disorders of mitochondrial fatty-acid oxidation share fasting-triggered hypoketotic hypoglycaemia, rhabdomyolysis, cardiomyopathy and arrhythmia, and TDD can present with acylcarnitine abnormalities suggestive of a beta-oxidation defect. They are distinguished by a consistent, diagnostic acylcarnitine profile and by the absence of the TDD neurodevelopmental and TANGO2-spell phenotype.

Show evidence (1 reference)

PMID:34668327 SUPPORT Human Clinical

"We present biochemical and clinical data to help highlight the features that aid in consideration of this condition in the differential with disorders of fatty acid oxidation."

Explicitly frames fatty-acid oxidation disorders as the key differential.

Primary mitochondrial disease

Overlapping Features TDD was initially classified among mitochondrial disorders, and secondary respiratory-chain and coenzyme Q10 abnormalities are reported in muscle. It is distinguished by the absence of a constitutive primary energetic defect, with normal interictal acylcarnitines, FGF-21, muscle histology and mitochondrial spectrometry in most patients.

Show evidence (2 references)

PMID:32929747 SUPPORT Human Clinical

"Mechanistically, TANGO2 disease is unlikely to originate from a primary mitochondrial defect."

Supports the distinction from primary mitochondrial cytopathy.

PMID:31339582 SUPPORT Human Clinical

"a defect of multiple respiratory chain enzymes and coenzyme Q10 (CoQ10 ) in two cases, suggesting a possible secondary defect of oxidative phosphorylation"

Recorded as PARTIAL because respiratory-chain abnormalities do occur in a minority, which is precisely why the differential is difficult; the authors interpret them as secondary.

Inherited long QT and Brugada syndromes

Overlapping Features TDD produces marked QTc prolongation and, in about a quarter of crises, a type I Brugada pattern, which can prompt a primary channelopathy diagnosis. TDD is distinguished by the crisis-conditional, metabolically triggered nature of the repolarization abnormality, its association with rhabdomyolysis and encephalopathy, and its poor response to standard antiarrhythmic drugs.

Show evidence (2 references)

PMID:35568137 SUPPORT Human Clinical

"During crisis, QTc prolongation occurred in all (median 547 ms; IQR 504-600 ms) and a type I Brugada pattern in 8 (26%)."

Documents the channelopathy-mimicking electrocardiographic phenotype.

PMID:38855866 SUPPORT Other

"TDD-associated cardiac arrhythmias are recalcitrant to standard antiarrhythmic medications and constitute the leading cause of death."

Supports the distinguishing feature of refractoriness to conventional antiarrhythmic therapy. Evidence source is OTHER because this is the framing statement of an iPSC-cardiomyocyte study.

🔬

Clinical Trials

1

NCT05374616 RECRUITING

Baylor College of Medicine observational natural-history study and biorepository for TANGO2-related disorder, collecting longitudinal clinical data plus blood, saliva and fibroblast specimens. It is non-interventional and is not a treatment-efficacy study, so it cannot resolve the open question of whether B-vitamin supplementation prevents crises; it is nonetheless the principal registered study in this disorder and the source of the natural-history cohorts cited throughout this entry.

Target Phenotypes: Encephalopathy HP:0001298 Ventricular tachycardia HP:0004756

Show evidence (1 reference)

clinicaltrials:NCT05374616 SUPPORT Human Clinical

"The study aims to establish a biorepository of individuals with TANGO2 deficiency to support scientific research and establish a comprehensive clinical database of affected individuals to understand the disease course."

The registry's own description of its biorepository and natural-history objectives.

🧫

Experimental Models

2

Patient-derived and CRISPR-engineered iPSC cardiomyocytes

Induced pluripotent stem cell-derived cardiomyocytes from individuals with TDD recapitulate the key electrophysiological abnormalities, and these are rescued by adenoviral wild-type TANGO2 expression or CRISPR correction of the pathogenic variant, establishing causality. An independent CRISPR line carrying the exon 3-9 deletion showed that the electrophysiological defect is substrate-conditional and mediated by ATP depletion and TRPM4 upregulation. This is currently the most disease-proximal platform for the arrhythmia arm.

Show evidence (2 references)

PMID:38855866 SUPPORT In Vitro

"Here, we established potentially novel patient-derived induced pluripotent stem cell differentiated cardiomyocyte (iPSC-CM) models that recapitulate key electrophysiological abnormalities in TDD. These electrophysiological abnormalities were rescued in iPSC-CMs with either adenoviral expression..."

Establishes the platform and its genetic-rescue validation.

PMID:42389941 SUPPORT In Vitro

"CRISPR/Cas9 were used to generate human induced pluripotent stem cell cardiomyocytes (hiPSC-CMs) carrying a TANGO2 exon 3-9 deletion (TANGO2-/-)."

Documents the independent isogenic CRISPR cardiomyocyte model.

Patient fibroblasts and primary myoblasts

Skin fibroblasts and primary myoblasts from affected individuals are the workhorse system for trafficking, lipidomic, respiration, reactive oxygen species and nutrient-stress assays, and they show reduced TANGO2 protein on immunoblot. They cannot model excitable tissue physiology.

Show evidence (2 references)

PMID:31339582 SUPPORT In Vitro

"Immunoblot analysis detected a significant decrease of TANGO2 protein."

Demonstrates that patient-derived cells report the molecular loss of function directly.

PMID:39722856 SUPPORT In Vitro

"Autophagy functioning was analyzed in vitro, in primary skeletal myoblasts from TANGO2 patients, in basal and fasting conditions"

Illustrates the use of patient primary myoblasts under nutrient stress.

🐁

Animal Models

3

tango2 loss-of-function mutant and morpholino knockdown Danio rerio Loss-of-function mutant and knockdown, with extrinsic stress challenge

Zebrafish tango2 mutants show growth defects, early lethality and heightened susceptibility of skeletal muscle to extrinsic triggers, closely mirroring the stress-conditional rhabdomyolysis of patients. Lipidomics in the same model identified glycerolipid-pathway alterations, and a separate knockdown study linked the rhabdomyolysis phenotype to autophagy and mitophagy failure with rescue by calpeptin. The model is well suited to trigger and rescue studies but does not reproduce the full human neurocardiac phenotype.

Species

Danio rerio

Genotype

tango2 loss-of-function mutant and morpholino knockdown

Genes

TANGO2 hgnc:25439

Show evidence (2 references)

PMID:37577943 SUPPORT Model Organism

"we demonstrate that the loss of Tango2 in zebrafish results in growth defects, early lethality and increased susceptibility of skeletal muscle defects in response to extrinsic triggers, similar to TANGO2-deficient patients"

Establishes the model and its recapitulation of trigger-dependent muscle injury.

PMID:39722856 SUPPORT Model Organism

"Calpeptin treatment was sufficient to rescue the locomotor properties thanks to its beneficial effect on autophagy functioning in zebrafish and to improve LC3-II levels in starved primary muscle cells of TANGO2 patients."

Demonstrates a pharmacological rescue acting through autophagy in the same model.

Constitutive Tango2 knockout and oligodendrocyte-specific conditional knockout Mus musculus Knockout and cell-type-specific conditional knockout, with vitamin B5 rescue

Constitutive and oligodendrocyte-specific Tango2 knockout mice reproduce the motor deficits of TDD, with cerebellar myelin loss and disturbed phospholipid metabolism that are alleviated by vitamin B5. An independent knockout line shows impaired intermediate-filament structure with fragmented mitochondrial networks and, in male mice, heart defects, reduced muscle function and glucose intolerance culminating in desminopathy. Earlier reports of grossly normal knockout mice mean that phenotype penetrance in mouse is line- and condition-dependent.

Species

Mus musculus

Genotype

Constitutive Tango2 knockout and oligodendrocyte-specific conditional knockout

Genes

TANGO2 hgnc:25439

Show evidence (2 references)

PMID:42522778 SUPPORT Model Organism

"Behavioral analyses revealed that both constitutive and oligodendrocyte-specific deletion of Tango2 recapitulate the motor deficits associated with individuals with TDD."

Establishes motor-phenotype recapitulation and its oligodendroglial origin.

PMID:40480980 SUPPORT Model Organism

"In male mice, loss of TANGO2 caused heart defects, reduced muscle function and glucose intolerance by remodelling of intermediate filaments, which altered the mitochondrial and cytoplasmic proteomes, N-glycosylation and nucleocytoplasmic O-GlcNAcylation."

Documents cardiac, muscular and metabolic phenotypes in an independent knockout line.

TANGO2 (CG31938) loss-of-function allele Drosophila melanogaster Loss-of-function mutant with starvation and heat-stress challenge and vitamin rescue

A Drosophila model of TANGO2 loss reproduces starvation sensitivity, heat-induced seizure susceptibility and locomotor impairment. It was the system in which vitamin B5 rescue was first demonstrated, with a weaker partial rescue by vitamin B3, and it provided the rationale for B-complex supplementation in patients.

Species

Drosophila melanogaster

Genotype

TANGO2 (CG31938) loss-of-function allele

Show evidence (2 references)

PMID:36502486 SUPPORT Model Organism

"Here, we describe a model of TANGO2-related disease in the fruit fly Drosophila melanogaster that recapitulates crucial disease traits."

Establishes the fly model and its recapitulation of disease traits.

PMID:36502486 SUPPORT Model Organism

"We also observed a partial rescue of one of the fly defects by vitamin B3, though to a lesser extent than vitamin B5."

Documents the vitamin specificity of the rescue in the fly model.

{ }

Source YAML

click to show

name: TANGO2 Deficiency Disorder
category: Mendelian
creation_date: "2026-07-31T00:00:00Z"
synonyms:
- TANGO2 deficiency
- TANGO2 deficiency disease
- TANGO2-related metabolic encephalopathy-arrhythmia syndrome
- TANGO2-related disorder
- MECRCN
- recurrent metabolic encephalomyopathic crises-rhabdomyolysis-cardiac arrhythmia-intellectual disability syndrome
description: >-
  TANGO2 deficiency disorder (TDD) is an ultra-rare autosomal recessive disorder
  caused by biallelic loss-of-function variants in TANGO2 (transport and Golgi
  organization 2 homolog), a gene at 22q11.21 whose product is required for
  intracellular lipid and membrane homeostasis and has been proposed, on
  biochemical evidence, to act as an acyl-CoA-binding protein. Affected
  individuals have baseline global developmental delay, intellectual disability,
  ataxia, dysarthria and hypothyroidism, punctuated by paroxysmal "TANGO2 spells"
  and by acute metabolic crises precipitated by catabolic stress such as fasting,
  febrile illness, dehydration, heat or exertion. Crises feature rhabdomyolysis
  with markedly elevated creatine kinase, hypoglycaemia, lactic acidosis,
  encephalopathy and life-threatening cardiac involvement with QT prolongation,
  ventricular tachycardia and cardiomyopathy; arrhythmia is the leading cause of
  death. Because TANGO2 lies within the region deleted in 22q11.2 deletion
  syndrome, a pathogenic variant on the remaining allele can unmask TDD as a
  second diagnosis. Daily B-complex/multivitamin supplementation (with
  pantothenate/B5 and folate/B9 as the best-supported active components) is an
  emerging crisis-prevention strategy backed by observational natural-history and
  model-system rescue data, but not yet by randomized trials.
disease_term:
  preferred_term: TANGO2 deficiency disorder
  term:
    id: MONDO:0018820
    label: recurrent metabolic encephalomyopathic crises-rhabdomyolysis-cardiac arrhythmia-intellectual disability syndrome
parents:
- Inborn Error of Metabolism
- Neurodegenerative Disease

references:
- reference: PMID:29369572
  title: TANGO2 Deficiency.
  tags:
  - GeneReviews

prevalence:
- population: Worldwide
  measure_type: POINT_PREVALENCE
  prevalence_class: BAND_1_9_PER_1000000
  rate_per_100000: 0.1
  notes: >-
    An expert-review extrapolation of roughly 8,000 affected individuals
    worldwide, corresponding to about 1 per million. This is not a
    registry-derived estimate; TDD is widely regarded as substantially
    underdiagnosed, particularly within 22q11.2 deletion syndrome.
  evidence:
  - reference: PMID:38836374
    reference_title: >-
      TANGO2 deficiency disease is predominantly caused by a lipid imbalance.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: TANGO2 deficiency disease (TDD) is a rare genetic disorder estimated to affect ∼8000 individuals worldwide.
    explanation: >-
      Supports the order-of-magnitude worldwide burden but is an estimate stated
      in a Perspective article rather than a measured population prevalence,
      hence PARTIAL.
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    The largest single natural-history cohort assembled to date comprised 73
    patients from 57 unrelated families across 16 countries.
  evidence:
  - reference: PMID:36473599
    reference_title: >-
      Natural history of TANGO2 deficiency disorder: Baseline assessment of 73 patients.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Data were collected from 73 patients (59% male) from 57 unrelated families living in 16 different countries.
    explanation: Quantifies the size of the largest reported TDD cohort.

progression:
- phase: Early infancy - apparently normal development
  age_range: birth to about 1 year
  notes: >-
    Development is typically normal in early infancy. The biallelic genotype is
    present from conception but produces no overt phenotype until milestones
    begin to lag.
  evidence:
  - reference: PMID:36473599
    reference_title: >-
      Natural history of TANGO2 deficiency disorder: Baseline assessment of 73 patients.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Patients showed normal development in early infancy, with progressive delay in developmental milestones thereafter.
    explanation: Establishes the normal early-infancy period preceding progressive milestone delay.
- phase: Baseline neurodevelopmental phenotype
  age_range: about 1 to 3 years onward
  notes: >-
    Progressive milestone delay emerges, with ataxia, dystonia and speech
    difficulties typically starting between 1 and 3 years, evolving into
    intellectual disability, dysarthria and paroxysmal TANGO2 spells.
  evidence:
  - reference: PMID:36473599
    reference_title: >-
      Natural history of TANGO2 deficiency disorder: Baseline assessment of 73 patients.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Symptoms included ataxia, dystonia, and speech difficulties, typically starting between the ages of 1 to 3 years.
    explanation: Fixes the age window in which the chronic neurological phenotype becomes manifest.
- phase: Episodic metabolic and cardiac crises
  age_range: childhood onward, median age 6.4 years at cardiac crisis admission
  notes: >-
    Superimposed on the chronic phenotype, catabolic stress precipitates
    metabolic crises with rhabdomyolysis and encephalopathy; about two-thirds of
    those who experience a metabolic crisis go on to have a cardiac crisis with
    QT prolongation and ventricular arrhythmia (30 of 71 individuals, 42%, in the
    natural-history cohort). Crisis manifestations including
    cardiomyopathy are often reversible, but each crisis carries a risk of
    sudden death.
  evidence:
  - reference: PMID:36473599
    reference_title: >-
      Natural history of TANGO2 deficiency disorder: Baseline assessment of 73 patients.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: A total of 46/71 (65%) patients suffered metabolic crises, and of those, 30 (65%) developed cardiac crises.
    explanation: Quantifies the proportion progressing from metabolic to cardiac crisis.
  - reference: PMID:35568137
    reference_title: >-
      Cardiac crises: Cardiac arrhythmias and cardiomyopathy during TANGO2 deficiency related metabolic crises.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Twenty-seven children were admitted for 43 cardiac crises (median age 6.4 years
    explanation: Gives the median age at cardiac crisis admission.
- phase: Long-term course and severity spectrum
  age_range: lifelong
  notes: >-
    The course is lifelong. Developmental disability generally persists and may
    step down after severe crises, while global brain atrophy accrues. Severity
    ranges from a fatal early-onset crisis to an adult limb-girdle myopathy
    phenotype, and a minority never experience an overt crisis; intrafamilial
    variability is marked even between siblings sharing a genotype, so genotype
    does not predict trajectory.
  evidence:
  - reference: PMID:42196371
    reference_title: >-
      Genetic and Clinical Characterization of TANGO2 Deficiency Disorder: Insights from the Italian Multicentre Cohort.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Clinical severity ranged from an asymptomatic individual under preventive therapy to a fatal early-onset metabolic crisis. Marked intrafamilial variability was observed in two siblings sharing the same genotype.
    explanation: Documents the breadth of the severity spectrum and intrafamilial variability.
  - reference: PMID:31276219
    reference_title: >-
      TANGO2 deficiency as a cause of neurodevelopmental delay with indirect effects on mitochondrial energy metabolism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Of importance, we identify two subjects (aged 12 and 17 years) who have never experienced any overt episode of the catabolism-induced metabolic crises typical for the disease.
    explanation: Shows that crises are not obligate and that a crisis-free course into adolescence is possible.
  - reference: PMID:26805782
    reference_title: >-
      Bi-allelic Truncating Mutations in TANGO2 Cause Infancy-Onset Recurrent Metabolic Crises with Encephalocardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Over the course of the disease, all individuals developed global brain atrophy with cognitive impairment and pyramidal signs.
    explanation: Documents the cumulative neurodegenerative component of the long-term course.

pathophysiology:
- name: Catabolic Stress Exposure
  biological_scale: ORGANISM
  role: trigger
  description: >-
    TDD is a stress-unmasked disorder: the biallelic genotype is present from
    conception, but the acute phenotype requires an extrinsic catabolic
    challenge. Established precipitants are intercurrent (especially febrile or
    viral) illness, fasting, dehydration, reduced oral intake, excessive heat,
    overexertion and a ketogenic diet. Some anaesthetic agents and, more
    tentatively, L-carnitine have been proposed as additional triggers, which
    makes specialist perioperative planning important.
  evidence:
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Triggers for TANGO2 spells and acute metabolic crises including fasting, dehydration, overexertion, exposure to excessive heat, ketogenic diet, and infections.
    explanation: >-
      Enumerates the established crisis precipitants. Evidence source is OTHER
      because this is a GeneReviews expert-consensus chapter rather than a
      primary study.
  - reference: PMID:32929747
    reference_title: >-
      Clinical and biological characterization of 20 patients with TANGO2 deficiency indicates novel triggers of metabolic crises and no primary energetic defect.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We show previously uncharacterized triggers of metabolic crises in TANGO2 patients, such as some anesthetics and possibly l-carnitine.
    explanation: Adds anaesthetic exposure as a trigger identified in the 20-patient French cohort; the l-carnitine association is explicitly hedged by the authors.
  downstream:
  - target: Catabolic-Stress Metabolic Decompensation
    description: >-
      Catabolic challenge raises substrate demand and shifts fuel use toward
      fatty acids in a system that cannot sustain that shift, converting the
      latent metabolic vulnerability into an acute crisis.

- name: TANGO2 Loss of Function
  biological_scale: MOLECULAR
  role: primary_defect
  description: >-
    Biallelic loss-of-function variants in TANGO2 - multiexon deletions
    (predominantly the recurrent exon 3-9 deletion), nonsense, frameshift,
    canonical splice-site and missense alleles - abolish or severely reduce
    TANGO2 protein. Purified TANGO2 binds acyl-coenzyme A, and mutation of its
    conserved NRDE motif abolishes that binding, leading its authors to propose
    that TANGO2 is an acyl-CoA-binding protein of the mitochondrial lumen.
    Separate imaging work localizes it predominantly to mitochondria and
    partially to mitochondrial sites juxtaposed to lipid droplets and the
    endoplasmic reticulum. An
    independent line of work identifies TANGO2 as a binding partner of the small
    heat-shock protein CRYAB that restrains desmin intermediate-filament
    aggregation, so the precise primary biochemical activity remains an area of
    active disagreement.
  genes:
  - preferred_term: TANGO2
    term:
      id: hgnc:25439
      label: TANGO2
  molecular_functions:
  - preferred_term: fatty-acyl-CoA binding
    term:
      id: GO:0000062
      label: fatty-acyl-CoA binding
    modifier: DECREASED
  cellular_components:
  - preferred_term: mitochondrion
    term:
      id: GO:0005739
      label: mitochondrion
  - preferred_term: lipid droplet
    term:
      id: GO:0005811
      label: lipid droplet
  mechanism_confidence: ESTABLISHED
  evidence:
  - reference: PMID:26805782
    reference_title: >-
      Bi-allelic Truncating Mutations in TANGO2 Cause Infancy-Onset Recurrent Metabolic Crises with Encephalocardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: By exome sequencing, we identified three different bi-allelic truncating mutations in TANGO2 in three unrelated individuals with infancy-onset episodic metabolic crises characterized by encephalopathy, hypoglycemia, rhabdomyolysis, arrhythmias, and laboratory findings suggestive of a defect in mitochondrial fatty acid oxidation.
    explanation: The gene-discovery paper establishing biallelic truncating TANGO2 variants as the cause of the disorder.
  - reference: PMID:40015245
    reference_title: >-
      TANGO2 is an acyl-CoA binding protein.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: We further show that purified TANGO2 binds acyl-coenzyme A, and mutations in the highly conserved NRDE sequence of TANGO2 inhibit this binding.
    explanation: Biochemical evidence assigning TANGO2 an acyl-CoA-binding molecular function.
  - reference: PMID:40015245
    reference_title: >-
      TANGO2 is an acyl-CoA binding protein.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: we demonstrate that TANGO2 localizes to the mitochondrial lumen via a structural region containing LIL residues
    explanation: Localizes the protein to the mitochondrial lumen, supporting the mitochondrial cellular-component annotation.
  - reference: PMID:36961129
    reference_title: >-
      Defects in lipid homeostasis reflect the function of TANGO2 in phospholipid and neutral lipid metabolism.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: We show that TANGO2 in mammalian cells localizes predominantly to mitochondria and partially at mitochondria sites juxtaposed to lipid droplets (LDs) and the endoplasmic reticulum.
    explanation: >-
      Sources the mitochondria-lipid-droplet-endoplasmic-reticulum contact-site
      localization and the lipid droplet cellular-component annotation on this node.
  - reference: PMID:40480980
    reference_title: >-
      TANGO2 binds crystallin alpha B and its loss causes desminopathy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: We identify that TANGO2 binds the small heat shock protein crystallin alpha B (CRYAB) to prevent the aggregation of the intermediate filament desmin and in the absence of TANGO2, mice develop desminopathy, which is consistent with features found in patients carrying mutations in either desmin or CRYAB.
    explanation: >-
      An alternative, mouse-and-cell-derived account of TANGO2 function via CRYAB
      and desmin. Marked PARTIAL because it proposes a different primary activity
      from the acyl-CoA-binding model and has not been reconciled with it in
      human tissue.
  downstream:
  - target: Lipid and Acyl-CoA Homeostasis Failure
    description: Loss of acyl-CoA handling starves downstream acylation and lipid-remodelling reactions.
  - target: Impaired ER-to-Golgi Membrane Trafficking
    description: Loss of TANGO2 slows secretory-pathway cargo transit, the phenotype for which the gene was originally named.
  - target: Oligodendroglial Lipid Dysregulation and Cerebellar Myelin Loss
    description: >-
      Cell-type-specific mouse deletion shows that TANGO2 loss in
      oligodendroglia is by itself sufficient to disturb phospholipid metabolism
      and myelin maintenance.

- name: Impaired ER-to-Golgi Membrane Trafficking
  biological_scale: CELLULAR
  description: >-
    Fibroblasts from affected individuals show a significant delay in movement of
    secretory cargo between the endoplasmic reticulum and the Golgi apparatus,
    attributable to loss of TANGO2 function, together with altered mitochondrial
    morphology. This trafficking arm is the defect most directly rescued by
    vitamin B5 in human cells, which is why it is retained as a distinct node
    even though its quantitative contribution to the acute crisis is not
    established.
  cell_types:
  - preferred_term: fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  biological_processes:
  - preferred_term: endoplasmic reticulum to Golgi vesicle-mediated transport
    term:
      id: GO:0006888
      label: endoplasmic reticulum to Golgi vesicle-mediated transport
    modifier: DECREASED
  cellular_components:
  - preferred_term: endoplasmic reticulum
    term:
      id: GO:0005783
      label: endoplasmic reticulum
  - preferred_term: Golgi apparatus
    term:
      id: GO:0005794
      label: Golgi apparatus
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:32909282
    reference_title: >-
      The phenotype associated with variants in TANGO2 may be explained by a dual role of the protein in ER-to-Golgi transport and at the mitochondria.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: there is a significant delay in the movement of cargo between the endoplasmic reticulum and the Golgi
    explanation: Direct measurement of the trafficking delay in patient-derived fibroblasts.
  - reference: PMID:32909282
    reference_title: >-
      The phenotype associated with variants in TANGO2 may be explained by a dual role of the protein in ER-to-Golgi transport and at the mitochondria.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: We further show that a portion of TANGO2 protein localizes to the mitochondria through a necessary but not sufficient stretch of amino acids at the amino terminus of the protein.
    explanation: Supports the dual trafficking-plus-mitochondrial account of the protein referenced in this node's description.
  - reference: PMID:31339582
    reference_title: >-
      Clinical presentation and proteomic signature of patients with TANGO2 mutations.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Proteomic analysis in fibroblasts revealed significant changes in components of the mitochondrial fatty acid oxidation, plasma membrane, endoplasmic reticulum-Golgi network and secretory pathways.
    explanation: Independent proteomic corroboration that the ER-Golgi and secretory compartments are perturbed.
  downstream:
  - target: Catabolic-Stress Metabolic Decompensation
    description: >-
      Secretory and membrane-transport impairment is proposed to reduce the
      cell's capacity to remodel membranes under stress; the causal weight of
      this edge relative to the lipid arm is not established.

- name: Lipid and Acyl-CoA Homeostasis Failure
  biological_scale: MOLECULAR
  role: central_effector
  description: >-
    Quantitative lipidomics of TANGO2-null HepG2 cells and patient fibroblasts
    shows a marked rise in lysophosphatidic acid with a reciprocal fall in its
    biosynthetic product phosphatidic acid, consistent with insufficient acyl-CoA
    available for LPA acylation. Triglyceride and lysophospholipid pools rise, the
    free fatty acid pool expands, and lipid droplets enlarge.
    The resulting defect in fatty-acid handling generates high levels of reactive
    oxygen species and promotes lipid peroxidation. Critically, these changes are
    exacerbated by nutrient starvation - the biochemical correlate of the clinical
    fasting trigger - and are reversed by vitamin B5 supplementation, which
    restores the coenzyme A precursor pool.
  chemical_entities:
  - preferred_term: phosphatidic acid
    term:
      id: CHEBI:16337
      label: phosphatidic acid
    modifier: DECREASED
  biological_processes:
  - preferred_term: glycerolipid metabolic process
    term:
      id: GO:0046486
      label: glycerolipid metabolic process
    modifier: ABNORMAL
  - preferred_term: phospholipid biosynthetic process
    term:
      id: GO:0008654
      label: phospholipid biosynthetic process
    modifier: DECREASED
  - preferred_term: cellular response to reactive oxygen species
    term:
      id: GO:0034614
      label: cellular response to reactive oxygen species
    modifier: INCREASED
  cellular_components:
  - preferred_term: lipid droplet
    term:
      id: GO:0005811
      label: lipid droplet
  mechanism_confidence: ESTABLISHED
  evidence:
  - reference: PMID:36961129
    reference_title: >-
      Defects in lipid homeostasis reflect the function of TANGO2 in phospholipid and neutral lipid metabolism.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Quantitative lipidomics revealed a marked increase in lysophosphatidic acid (LPA) and a concomitant decrease in its biosynthetic precursor phosphatidic acid (PA). These changes were exacerbated in nutrient-starved cells.
    explanation: The core lipidomic signature, and its worsening under the nutrient stress that clinically triggers crises.
  - reference: PMID:36961129
    reference_title: >-
      Defects in lipid homeostasis reflect the function of TANGO2 in phospholipid and neutral lipid metabolism.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: The defect in acyl-CoA availability impacts the metabolism of many other fatty acids, generates high levels of reactive oxygen species, and promotes lipid peroxidation.
    explanation: Links the acyl-CoA defect to oxidative injury, the bridge from lipid imbalance to tissue damage.
  - reference: PMID:38718569
    reference_title: >-
      Lipidomic analysis of human TANGO2-deficient cells suggests a lipid imbalance as a cause of TANGO2 deficiency disease.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: we found profound changes in the lipid profile of human TANGO2-deficient cells
    explanation: Independent lipidomic replication of the lipid-profile abnormality in human TANGO2-deficient cells.
  - reference: PMID:38718569
    reference_title: >-
      Lipidomic analysis of human TANGO2-deficient cells suggests a lipid imbalance as a cause of TANGO2 deficiency disease.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: an increased pool of free fatty acids in both human cells devoid of TANGO2 and Drosophila harboring a previously described TANGO2 loss of function allele. All these changes were reversed upon vitamin B5 supplementation.
    explanation: >-
      Cross-species (Drosophila) replication of the free-fatty-acid expansion and
      its reversal by vitamin B5, which ties this node to the therapeutic
      rationale.
  - reference: PMID:37577943
    reference_title: >-
      Intrinsic and extrinsic regulation of rhabdomyolysis susceptibility by Tango2.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Using lipidomics, we identified alterations in the glycerolipid pathway in tango2 mutants, which is critical for membrane stability and energy balance.
    explanation: Cross-species (zebrafish) confirmation that the glycerolipid pathway is the affected axis.
  downstream:
  - target: Impaired Mitochondrial Fatty-Acid Oxidation and Energy Reserve
    description: >-
      Restricted acyl-CoA supply and disordered membrane phospholipid composition
      degrade the capacity of mitochondria to oxidize fatty acids and to sustain
      ATP output under load.

- name: Impaired Mitochondrial Fatty-Acid Oxidation and Energy Reserve
  biological_scale: CELLULAR
  conforms_to: "metabolic_intoxication_decompensation#Toxic Metabolite Accumulation and Energy Deficit"
  description: >-
    Mutant fibroblasts show a functional defect of palmitate-dependent
    respiration, and CRISPR-engineered TANGO2-null iPSC-derived cardiomyocytes
    have normal bioenergetics on glucose but a profound fall in ATP production
    rate and ATP/ADP ratio when forced to use palmitate, worsened by 24-hour
    fasting. Muscle histology and respiratory-chain studies in patients are often
    unremarkable at baseline, and plasma acylcarnitines and FGF-21 are usually
    normal between episodes: the deficit is a conditional, substrate-dependent
    loss of energy reserve rather than a constitutive respiratory-chain enzyme
    deficiency. Autophagy and mitophagy are additionally impaired on starvation,
    limiting the clearance of damaged organelles. This node conforms to the
    module's toxic-metabolite/energy-deficit stage on the energy-deficit arm; the
    accumulating species in TDD are lysophospholipids and free fatty acids rather
    than a classical organic acid.
  biological_processes:
  - preferred_term: fatty acid beta-oxidation
    term:
      id: GO:0006635
      label: fatty acid beta-oxidation
    modifier: DECREASED
  - preferred_term: autophagy
    term:
      id: GO:0006914
      label: autophagy
    modifier: DECREASED
  cellular_components:
  - preferred_term: mitochondrion
    term:
      id: GO:0005739
      label: mitochondrion
  mechanism_confidence: ESTABLISHED
  evidence:
  - reference: PMID:26805782
    reference_title: >-
      Bi-allelic Truncating Mutations in TANGO2 Cause Infancy-Onset Recurrent Metabolic Crises with Encephalocardiomyopathy.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Investigation of palmitate-dependent respiration in mutant fibroblasts showed evidence of a functional defect in mitochondrial β-oxidation.
    explanation: First functional demonstration of impaired fatty-acid oxidation in patient cells.
  - reference: PMID:42389941
    reference_title: >-
      Metabolic crisis and TRPM4 activation cause QT prolongation in TANGO2 deficiency disorder.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: using palmitate as energy substrate triggered a profound reduction in cellular ATP production rate and decreased ATP/ADP ratios in TANGO2-/- hiPSC-CMs, exacerbated by 24-hour fasting. This crisis was prevented by 2-week treatment with vitamins B5 and B9.
    explanation: >-
      Shows the deficit is substrate-conditional (present on palmitate, absent on
      glucose) and fasting-amplified, and that B-vitamin pretreatment prevents it.
  - reference: PMID:32929747
    reference_title: >-
      Clinical and biological characterization of 20 patients with TANGO2 deficiency indicates novel triggers of metabolic crises and no primary energetic defect.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Mechanistically, TANGO2 disease is unlikely to originate from a primary mitochondrial defect. Rather, we suggest that mitochondrial defects are secondary to strong extrinsic triggers in TANGO2 deficient patients.
    explanation: >-
      Constrains the claim: this node is a secondary, stress-dependent
      mitochondrial deficit, not a primary respiratory-chain disorder. Recorded
      as PARTIAL because it refutes the strong version of the mitochondrial
      hypothesis while supporting the conditional version modelled here.
  - reference: PMID:39722856
    reference_title: >-
      TANGO2-related rhabdomyolysis symptoms are associated with abnormal autophagy functioning.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: TANGO2 mutations were associated with reduced LC3-II levels upon starvation
    explanation: Adds a starvation-conditional autophagy defect in patient primary myoblasts.
  downstream:
  - target: Catabolic-Stress Metabolic Decompensation
    description: >-
      Once fatty acids become the dominant fuel during fasting or febrile
      illness, the exhausted energy reserve tips high-demand tissues into overt
      decompensation.

- name: Catabolic-Stress Metabolic Decompensation
  biological_scale: ORGANISM
  role: central_effector
  conforms_to: "metabolic_intoxication_decompensation#Acute Metabolic Decompensation"
  description: >-
    The acute crisis is the shared central effector of the disorder. It manifests
    as hypoglycaemia, lactic and metabolic acidosis, markedly elevated creatine
    kinase and transaminases, and encephalopathy, and it converts the latent
    cellular lesion into simultaneous multi-organ injury of skeletal muscle,
    brain and heart. Between episodes, standard metabolic screening is frequently
    normal, so a normal baseline workup does not exclude the diagnosis.
  biological_processes:
  - preferred_term: glucose homeostasis
    term:
      id: GO:0042593
      label: glucose homeostasis
    modifier: ABNORMAL
  - preferred_term: fatty acid metabolic process
    term:
      id: GO:0006631
      label: fatty acid metabolic process
    modifier: ABNORMAL
  mechanism_confidence: ESTABLISHED
  evidence:
  - reference: PMID:32909282
    reference_title: >-
      The phenotype associated with variants in TANGO2 may be explained by a dual role of the protein in ER-to-Golgi transport and at the mitochondria.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: TANGO2 variants result in a complex disease phenotype consisting of recurrent crisis-induced rhabdomyolysis, encephalopathy, seizures, lactic acidosis, hypoglycemia, and cardiac arrhythmias.
    explanation: >-
      Enumerates the biochemical and clinical content of the decompensated state.
      Evidence source is OTHER because this is the background statement of an
      in vitro trafficking study, not its own clinical observation.
  - reference: PMID:31339582
    reference_title: >-
      Clinical presentation and proteomic signature of patients with TANGO2 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Transport And Golgi Organization protein 2 (TANGO2) deficiency has recently been identified as a rare metabolic disorder with a distinct clinical and biochemical phenotype of recurrent metabolic crises, hypoglycemia, lactic acidosis, rhabdomyolysis, arrhythmias, and encephalopathy with cognitive decline.
    explanation: Independent characterization of the same decompensation syndrome.
  - reference: PMID:32929747
    reference_title: >-
      Clinical and biological characterization of 20 patients with TANGO2 deficiency indicates novel triggers of metabolic crises and no primary energetic defect.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Unexpectedly, plasma acylcarnitines, plasma FGF-21, muscle histology, and mitochondrial spectrometry were mostly normal.
    explanation: Supports the statement that interictal biochemical screening is typically unrevealing.
  downstream:
  - target: Skeletal Myofiber Necrosis and Rhabdomyolysis
    description: Energy failure in the highest-demand striated tissue produces myofiber necrosis with release of creatine kinase and myoglobin.
  - target: Acute Metabolic Encephalopathy
    description: Hypoglycaemia, acidosis and neuronal energy failure produce acute encephalopathy and seizures during the crisis.
  - target: Cardiomyocyte ATP Depletion and Repolarization Instability
    description: Cardiomyocytes forced onto fatty-acid fuel during the crisis lose ATP and destabilize repolarization.

- name: Skeletal Myofiber Necrosis and Rhabdomyolysis
  biological_scale: TISSUE
  description: >-
    Skeletal muscle is the tissue most consistently injured during crises.
    Myofibers undergo necrosis with release of creatine kinase and myoglobin,
    producing myoglobinuria and, when severe, acute kidney injury. Zebrafish
    tango2 mutants reproduce this stress-conditional muscle vulnerability, showing
    increased skeletal-muscle susceptibility to extrinsic triggers; the same model
    links the injury to failed autophagy and mitophagy.
    Chronic myopathic change with endomysial fibrosis is documented at the mild
    end of the spectrum.
  cell_types:
  - preferred_term: skeletal muscle cell
    term:
      id: CL:0000188
      label: cell of skeletal muscle
  locations:
  - preferred_term: skeletal muscle tissue
    term:
      id: UBERON:0001134
      label: skeletal muscle tissue
  biological_processes:
  - preferred_term: lipid catabolic process
    term:
      id: GO:0016042
      label: lipid catabolic process
    modifier: ABNORMAL
  mechanism_confidence: ESTABLISHED
  evidence:
  - reference: PMID:37577943
    reference_title: >-
      Intrinsic and extrinsic regulation of rhabdomyolysis susceptibility by Tango2.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: the loss of Tango2 in zebrafish results in growth defects, early lethality and increased susceptibility of skeletal muscle defects in response to extrinsic triggers, similar to TANGO2-deficient patients
    explanation: Model-organism recapitulation of trigger-dependent skeletal muscle injury.
  - reference: PMID:39722856
    reference_title: >-
      TANGO2-related rhabdomyolysis symptoms are associated with abnormal autophagy functioning.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: rhabdomyolysis features of tango2 knockdown were associated with autophagy and mitophagy defects in zebrafish
    explanation: Mechanistically connects the muscle injury to impaired autophagic clearance.
  - reference: PMID:37119590
    reference_title: >-
      Limb-girdle myopathy and mild intellectual disability: The expanding spectrum of TANGO2-related disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Muscle histology two years later revealed increased endomysial fibrosis and other myopathic changes.
    explanation: Documents chronic structural muscle damage persisting between crises in a human case.

- name: Acute Metabolic Encephalopathy
  biological_scale: ORGANISM
  conforms_to: "metabolic_intoxication_decompensation#Acute Metabolic Encephalopathy"
  description: >-
    During crises, neuronal energy failure compounded by hypoglycaemia and lactic
    acidosis produces acute encephalopathy ranging from lethargy and
    disorientation to seizures and coma. Unlike the classical intoxication-type
    inborn errors, ammonia neurotoxicity is not the dominant driver in TDD; the
    conformance to the module is therefore on the shared energy-failure and
    acidosis route to acute encephalopathy rather than on the ammonia-glutamine
    astrocyte-swelling route.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  locations:
  - preferred_term: brain
    term:
      id: UBERON:0000955
      label: brain
  mechanism_confidence: ESTABLISHED
  evidence:
  - reference: PMID:26805782
    reference_title: >-
      Bi-allelic Truncating Mutations in TANGO2 Cause Infancy-Onset Recurrent Metabolic Crises with Encephalocardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: three unrelated individuals with infancy-onset episodic metabolic crises characterized by encephalopathy, hypoglycemia, rhabdomyolysis, arrhythmias
    explanation: Places encephalopathy within the crisis syndrome alongside hypoglycaemia.
  - reference: PMID:30245509
    reference_title: >-
      TANGO2: expanding the clinical phenotype and spectrum of pathogenic variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Primary features include metabolic crisis with rhabdomyolysis, encephalopathy, intellectual disability, seizures, and cardiac arrhythmias.
    explanation: Independent case-series confirmation that encephalopathy is a primary crisis feature.
  downstream:
  - target: Progressive Neurodegeneration and Regression
    description: Repeated encephalopathic episodes contribute to stepwise loss of acquired skills superimposed on the baseline neurodevelopmental course.

- name: Cardiomyocyte ATP Depletion and Repolarization Instability
  biological_scale: CELLULAR
  conforms_to: "cardiac_ion_channel_repolarization#Altered Action Potential and Calcium Handling"
  description: >-
    In TANGO2-null iPSC-derived cardiomyocytes, the palmitate-driven collapse of
    the ATP/ADP ratio prolongs the action potential; the prolongation is
    abolished by intracellular delivery of Mg-ATP or creatine kinase, showing it
    is energy-dependent rather than a primary channel defect. The metabolic crisis
    upregulates TRPM4, an ATP- and calcium-regulated cation channel, and TRPM4
    knockdown or block prevents action-potential prolongation without correcting
    the energy deficit. L-type calcium channel inhibition with verapamil also
    prevents prolongation by normalizing ATP/ADP and intracellular calcium
    handling. Conformance to the channelopathy module is declared here on the
    altered-action-potential/calcium-handling stage only: TDD reaches that stage
    through a metabolic route, not through an inherited ion-channel variant, so
    the module's trigger node is deliberately not claimed.
  cell_types:
  - preferred_term: cardiomyocyte
    term:
      id: CL:0000746
      label: cardiac muscle cell
  biological_processes:
  - preferred_term: cardiac muscle cell action potential
    term:
      id: GO:0086001
      label: cardiac muscle cell action potential
    modifier: ABNORMAL
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:42389941
    reference_title: >-
      Metabolic crisis and TRPM4 activation cause QT prolongation in TANGO2 deficiency disorder.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: During the crisis, TANGO2-/- hiPSC-CMs exhibited AP prolongation, prevented by intracellular delivery of Mg-ATP or creatine kinase.
    explanation: Establishes that action-potential prolongation is directly caused by the cardiomyocyte energy deficit.
  - reference: PMID:42389941
    reference_title: >-
      Metabolic crisis and TRPM4 activation cause QT prolongation in TANGO2 deficiency disorder.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Importantly, the metabolic crisis upregulated TRPM4, an ATP- and Ca-regulated channel. TRPM4 siRNA knockdown or pharmacological block prevented AP prolongation without rescuing the energetic deficit of TANGO2-/- hiPSC-CMs.
    explanation: Identifies TRPM4 as the effector channel translating ATP deficiency into repolarization abnormality.
  - reference: PMID:42389941
    reference_title: >-
      Metabolic crisis and TRPM4 activation cause QT prolongation in TANGO2 deficiency disorder.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: LTCC inhibition with verapamil prevented AP prolongation by normalizing ATP/ADP ratios and intracellular Ca mishandling.
    explanation: Documents disturbed intracellular calcium handling and its pharmacological correction.
  downstream:
  - target: Arrhythmogenic Substrate and Triggered Activity
    description: Prolonged, heterogeneous repolarization across the ventricular wall creates the substrate for triggered beats and reentry.

- name: Arrhythmogenic Substrate and Triggered Activity
  biological_scale: TISSUE
  conforms_to: "cardiac_ion_channel_repolarization#Arrhythmogenic Substrate and Triggered Activity"
  description: >-
    At the tissue level the cellular repolarization defect appears as marked QTc
    prolongation, which is present in essentially every documented TDD cardiac
    crisis (median QTc 547 ms in a 27-patient multicentre series), and in a
    minority as a type I Brugada pattern. The resulting dispersion of
    repolarization is the substrate on which triggered beats initiate ventricular
    arrhythmia.
  cell_types:
  - preferred_term: cardiomyocyte
    term:
      id: CL:0000746
      label: cardiac muscle cell
  locations:
  - preferred_term: heart
    term:
      id: UBERON:0000948
      label: heart
  biological_processes:
  - preferred_term: cardiac conduction
    term:
      id: GO:0061337
      label: cardiac conduction
    modifier: DYSREGULATED
  mechanism_confidence: ESTABLISHED
  evidence:
  - reference: PMID:35568137
    reference_title: >-
      Cardiac crises: Cardiac arrhythmias and cardiomyopathy during TANGO2 deficiency related metabolic crises.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: During crisis, QTc prolongation occurred in all (median 547 ms; IQR 504-600 ms) and a type I Brugada pattern in 8 (26%).
    explanation: Quantifies universal QTc prolongation within cardiac crises, with the median value and the Brugada-pattern minority.
  - reference: PMID:42389941
    reference_title: >-
      Metabolic crisis and TRPM4 activation cause QT prolongation in TANGO2 deficiency disorder.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: These findings suggest a mechanistic link between ATP deficiency, TRPM4 activation, and AP prolongation in TDD.
    explanation: Supplies the mechanistic chain connecting the cellular node to this tissue-level substrate.
  downstream:
  - target: Ventricular Tachyarrhythmia and Cardiac Arrest
    description: Triggered beats on a dispersed-repolarization substrate degenerate into ventricular tachycardia, torsade de pointes and cardiac arrest.

- name: Ventricular Tachyarrhythmia and Cardiac Arrest
  biological_scale: ORGANISM
  conforms_to: "cardiac_ion_channel_repolarization#Ventricular Tachyarrhythmia"
  description: >-
    Ventricular tachycardia occurred in 78% and cardiac arrest in 74% of patients
    admitted with a TDD cardiac crisis, with cardiomyopathy in 70% and 37%
    mortality, six of ten deaths arrhythmia-related. These arrhythmias are
    recalcitrant to standard antiarrhythmic drugs and constitute the leading cause
    of death in the disorder, which is why they are modelled as the terminal node
    of the cardiac arm.
  locations:
  - preferred_term: heart
    term:
      id: UBERON:0000948
      label: heart
  mechanism_confidence: ESTABLISHED
  evidence:
  - reference: PMID:35568137
    reference_title: >-
      Cardiac crises: Cardiac arrhythmias and cardiomyopathy during TANGO2 deficiency related metabolic crises.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Arrhythmias included VT in 21 (78%), supraventricular tachycardia in 3 (11%), and heart block in 1 (4%). Nineteen patients (70%) developed cardiomyopathy, and 20 (74%) experienced a cardiac arrest. There were 10 deaths (37%), 6 related to arrhythmias.
    explanation: The primary quantitative outcome data for the cardiac arm within crisis admissions.
  - reference: PMID:38855866
    reference_title: >-
      Folate as a potential treatment for lethal ventricular arrhythmias in TANGO2-deficiency disorder.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: TDD-associated cardiac arrhythmias are recalcitrant to standard antiarrhythmic medications and constitute the leading cause of death.
    explanation: >-
      Establishes arrhythmia as the leading cause of death and its refractoriness
      to conventional therapy. Evidence source is OTHER because this is the
      framing statement of an iPSC-cardiomyocyte study rather than its own
      clinical result; the mortality figures themselves are cited from
      PMID:35568137 elsewhere in this entry.

- name: Oligodendroglial Lipid Dysregulation and Cerebellar Myelin Loss
  biological_scale: CELLULAR
  description: >-
    Constitutive and oligodendrocyte-specific Tango2 knockout mice both reproduce
    the motor deficits seen in TDD, with robust cerebellar myelin loss, increased
    cerebellar synapse number, and downregulation of phospholipid-metabolism
    programmes. Vitamin B5 supplementation alleviates both the motor deficit and
    the myelin defect. This provides a cell-autonomous, non-crisis route from
    TANGO2 loss to the chronic ataxia and motor phenotype; it is a mouse finding
    not yet confirmed in human tissue.
  cell_types:
  - preferred_term: oligodendrocyte
    term:
      id: CL:0000128
      label: oligodendrocyte
  locations:
  - preferred_term: cerebellum
    term:
      id: UBERON:0002037
      label: cerebellum
  biological_processes:
  - preferred_term: phospholipid biosynthetic process
    term:
      id: GO:0008654
      label: phospholipid biosynthetic process
    modifier: DECREASED
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:42522778
    reference_title: >-
      Oligodendroglial TANGO2 Regulates Lipid Metabolism to Control Motor Coordination.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Behavioral analyses revealed that both constitutive and oligodendrocyte-specific deletion of Tango2 recapitulate the motor deficits associated with individuals with TDD.
    explanation: Shows the motor phenotype is attributable to oligodendroglial TANGO2 loss specifically.
  - reference: PMID:42522778
    reference_title: >-
      Oligodendroglial TANGO2 Regulates Lipid Metabolism to Control Motor Coordination.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Morphological quantifications further showed that Tango2 deletion led to robust cerebellar myelin loss and an increase in synapse number in the cerebellar cortex.
    explanation: Provides the structural cerebellar correlate of the motor deficit.
  downstream:
  - target: Progressive Neurodegeneration and Regression
    description: Cerebellar myelin loss contributes to the chronic ataxia, dysarthria and motor decline independently of acute crises.

- name: Progressive Neurodegeneration and Regression
  biological_scale: ORGANISM
  description: >-
    Over the course of the disease, individuals develop global brain atrophy with
    cognitive impairment and pyramidal signs. Neuroimaging shows variable cerebral
    and white-matter atrophy and ventriculomegaly. Post-mortem examination in one
    case revealed heterotopic neurons in the cerebral white matter, raising the
    possibility of an additional neuronal-migration contribution to the
    neurodevelopmental phenotype.
  locations:
  - preferred_term: brain
    term:
      id: UBERON:0000955
      label: brain
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  mechanism_confidence: ESTABLISHED
  evidence:
  - reference: PMID:26805782
    reference_title: >-
      Bi-allelic Truncating Mutations in TANGO2 Cause Infancy-Onset Recurrent Metabolic Crises with Encephalocardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Over the course of the disease, all individuals developed global brain atrophy with cognitive impairment and pyramidal signs.
    explanation: Documents the progressive neurodegenerative trajectory in the index cohort.
  - reference: PMID:31276219
    reference_title: >-
      TANGO2 deficiency as a cause of neurodevelopmental delay with indirect effects on mitochondrial energy metabolism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In one deceased patient, post-mortem autopsy revealed heterotopic neurons in the cerebral white matter, indicating a possible role for TANGO2 in neuronal migration.
    explanation: >-
      A single autopsy observation; recorded as PARTIAL because a
      neuronal-migration role is explicitly framed by the authors as a
      possibility, not an established mechanism.

phenotypes:
- category: Neurologic
  name: Global Developmental Delay
  description: >-
    Baseline neurodevelopmental impairment is the most consistent chronic feature.
    Development is typically normal in early infancy with progressive milestone
    delay thereafter, evolving into intellectual disability with prominent speech
    difficulties. In the 20-patient French cohort neurodevelopmental delay was
    present in 17 of 20 (85%).
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
    clinical_course: PROGRESSIVE
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:32929747
    reference_title: >-
      Clinical and biological characterization of 20 patients with TANGO2 deficiency indicates novel triggers of metabolic crises and no primary energetic defect.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Here, we describe a cohort of 20 French patients bearing mutations in the TANGO2 gene. We found that the main clinical presentation was the association of neurodevelopmental delay (n = 17), acute metabolic crises (n = 17) and hypothyroidism (n = 12), with a large intrafamilial clinical variability.
    explanation: >-
      Gives both numerator and denominator (17/20 = 85%), which falls in the
      VERY_FREQUENT band (99-80%).
  - reference: PMID:31276219
    reference_title: >-
      TANGO2 deficiency as a cause of neurodevelopmental delay with indirect effects on mitochondrial energy metabolism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: All patients showed developmental delay with ataxia, dysarthria, intellectual disability, or signs of spastic diplegia.
    explanation: Independent series confirming universal developmental delay in its cohort.

- category: Neurologic
  name: Intellectual Disability
  description: >-
    Cognitive impairment persists and often worsens after crises; attentional
    difficulties are a recurrent feature on standardized neurodevelopmental
    assessment.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  frequency: FREQUENT
  evidence:
  - reference: PMID:34668327
    reference_title: >-
      Variable clinical severity in TANGO2 deficiency: Case series and literature review.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Common clinical features seen in >70% of all individuals include acute metabolic crisis, rhabdomyolysis, neurologic abnormalities, developmental delay, and intellectual disability.
    explanation: >-
      A pooled review of 92 individuals reporting intellectual disability in more
      than 70%. The stated floor is consistent with the FREQUENT band (79-30%);
      the band is assigned conservatively because the source gives only a lower
      bound.

- category: Neurologic
  name: Ataxia
  description: >-
    Gait incoordination typically emerges between 1 and 3 years and is among the
    most disabling chronic features, contributing to falls and progressive loss of
    mobility. It also worsens acutely during TANGO2 spells.
  phenotype_term:
    preferred_term: Ataxia
    term:
      id: HP:0001251
      label: Ataxia
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:36473599
    reference_title: >-
      Natural history of TANGO2 deficiency disorder: Baseline assessment of 73 patients.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Symptoms included ataxia, dystonia, and speech difficulties, typically starting between the ages of 1 to 3 years.
    explanation: Establishes ataxia and its typical age of onset in the 73-patient natural-history cohort.
  - reference: PMID:31276219
    reference_title: >-
      TANGO2 deficiency as a cause of neurodevelopmental delay with indirect effects on mitochondrial energy metabolism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: All patients showed developmental delay with ataxia, dysarthria, intellectual disability, or signs of spastic diplegia.
    explanation: Independent series naming ataxia as a core neurological feature.

- category: Neurologic
  name: Dysarthria
  description: Slurred, effortful speech that characteristically worsens acutely during TANGO2 spells.
  phenotype_term:
    preferred_term: Dysarthria
    term:
      id: HP:0001260
      label: Dysarthria
  evidence:
  - reference: PMID:31276219
    reference_title: >-
      TANGO2 deficiency as a cause of neurodevelopmental delay with indirect effects on mitochondrial energy metabolism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: All patients showed developmental delay with ataxia, dysarthria, intellectual disability, or signs of spastic diplegia.
    explanation: Names dysarthria among the core chronic neurological features.
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: including sudden onset of hypotonia, ataxia with loss of balance, head and body tilt, increased dysarthria, drooling, lethargy, and disorientation
    explanation: >-
      Documents acute worsening of dysarthria during spells. Evidence source is
      OTHER because this is a GeneReviews expert-consensus chapter.

- category: Neurologic
  name: TANGO2 Spells
  description: >-
    Paroxysmal, non-life-threatening episodes of acutely worsened baseline
    neurological function - sudden hypotonia, ataxia with loss of balance, head
    and body tilt, increased dysarthria, drooling, lethargy and disorientation -
    lasting minutes to hours. They are distinguished from metabolic crises by the
    absence of rhabdomyolysis and cardiac involvement, and are the single most
    characteristic episodic feature of the disorder.
  phenotype_term:
    preferred_term: Episodic ataxia
    term:
      id: HP:0002131
      label: Episodic ataxia
    temporality: RECURRENT
  diagnostic: true
  evidence:
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Most individuals have TANGO2 spells, non-life-threatening paroxysmal worsening of baseline symptoms, including sudden onset of hypotonia, ataxia with loss of balance, head and body tilt, increased dysarthria, drooling, lethargy, and disorientation.
    explanation: >-
      Defines the spell phenotype and its distinction from metabolic crises.
      Evidence source is OTHER because this is a GeneReviews chapter.

- category: Neurologic
  name: Seizures
  description: >-
    Childhood-onset seizures, sometimes treatment-resistant; generalized and
    myoclonic semiologies are reported, and prolonged post-ictal coma can occur.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: TANGO2 deficiency is characterized by developmental delay, intellectual disability, gait incoordination, speech difficulties, seizures, and hypothyroidism.
    explanation: >-
      Places seizures among the core chronic features. Evidence source is OTHER
      because this is a GeneReviews chapter.
  - reference: PMID:30245509
    reference_title: >-
      TANGO2: expanding the clinical phenotype and spectrum of pathogenic variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Primary features include metabolic crisis with rhabdomyolysis, encephalopathy, intellectual disability, seizures, and cardiac arrhythmias.
    explanation: Independent case-series confirmation.

- category: Neurologic
  name: Developmental Regression
  description: >-
    Loss of previously acquired skills, notably expressive language and
    independent mobility, often stepwise after a severe crisis and superimposed on
    the baseline developmental trajectory.
  phenotype_term:
    preferred_term: Developmental regression
    term:
      id: HP:0002376
      label: Developmental regression
  evidence:
  - reference: PMID:36502486
    reference_title: >-
      Vitamin B5, a coenzyme A precursor, rescues TANGO2 deficiency disease-associated defects in Drosophila and human cells.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Mutations in the Transport and Golgi Organization 2 (TANGO2) gene are associated with intellectual deficit, neurodevelopmental delay and regression.
    explanation: >-
      Names regression explicitly as part of the TANGO2 phenotype. Evidence
      source is OTHER because this is the background statement of a Drosophila
      and human-cell study.
  - reference: PMID:39641377
    reference_title: >-
      Vitamin B5 Monotherapy Improves Symptoms in a 7-Year-Old Girl With TANGO2 Deficiency Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: A 7-year-old Chinese girl presented with epilepsy, developmental delay, neuroregression, and episodes of dyskinesia.
    explanation: Direct clinical documentation of neuroregression in an affected child.

- category: Neurologic
  name: Cerebral Atrophy
  description: >-
    Progressive global brain atrophy with white-matter change and ventriculomegaly
    develops over the course of the disease, accompanied by cognitive decline and
    pyramidal signs.
  phenotype_term:
    preferred_term: Cerebral atrophy
    term:
      id: HP:0002059
      label: Cerebral atrophy
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:26805782
    reference_title: >-
      Bi-allelic Truncating Mutations in TANGO2 Cause Infancy-Onset Recurrent Metabolic Crises with Encephalocardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Over the course of the disease, all individuals developed global brain atrophy with cognitive impairment and pyramidal signs.
    explanation: Directly documents progressive global brain atrophy.

- category: Neurologic
  name: Dystonia
  description: Dystonic posturing, typically emerging in early childhood alongside ataxia and speech difficulty.
  phenotype_term:
    preferred_term: Dystonia
    term:
      id: HP:0001332
      label: Dystonia
  evidence:
  - reference: PMID:36473599
    reference_title: >-
      Natural history of TANGO2 deficiency disorder: Baseline assessment of 73 patients.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Symptoms included ataxia, dystonia, and speech difficulties, typically starting between the ages of 1 to 3 years.
    explanation: Names dystonia among the core early motor features of the natural-history cohort.

- category: Neurologic
  name: Delayed Speech and Language Development
  description: >-
    Speech difficulty is listed among the core clinical characteristics of the
    disorder and typically emerges with the other early motor findings between 1
    and 3 years. It is distinct from, and often coexists with, the dysarthria
    that worsens acutely during spells.
  phenotype_term:
    preferred_term: Delayed speech and language development
    term:
      id: HP:0000750
      label: Delayed speech and language development
  evidence:
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: TANGO2 deficiency is characterized by developmental delay, intellectual disability, gait incoordination, speech difficulties, seizures, and hypothyroidism.
    explanation: >-
      Lists speech difficulties among the core clinical characteristics.
      Evidence source is OTHER because this is a GeneReviews chapter.
  - reference: PMID:36473599
    reference_title: >-
      "Natural history of TANGO2 deficiency disorder: Baseline assessment of 73 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Symptoms included ataxia, dystonia, and speech difficulties, typically starting between the ages of 1 to 3 years.
    explanation: Places speech difficulty in the early-childhood onset window in the 73-patient cohort.

- category: Neurologic
  name: Spasticity
  description: >-
    Pyramidal signs including spastic diplegia are part of the chronic
    neurological phenotype and contribute, with ataxia and dystonia, to
    progressive mobility loss.
  phenotype_term:
    preferred_term: Spasticity
    term:
      id: HP:0001257
      label: Spasticity
  evidence:
  - reference: PMID:31276219
    reference_title: >-
      TANGO2 deficiency as a cause of neurodevelopmental delay with indirect effects on mitochondrial energy metabolism.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: All patients showed developmental delay with ataxia, dysarthria, intellectual disability, or signs of spastic diplegia.
    explanation: Names spastic diplegia among the chronic neurological findings of the cohort.
  - reference: PMID:26805782
    reference_title: >-
      Bi-allelic Truncating Mutations in TANGO2 Cause Infancy-Onset Recurrent Metabolic Crises with Encephalocardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: all individuals developed global brain atrophy with cognitive impairment and pyramidal signs
    explanation: Independent documentation of pyramidal signs in the index cohort.

- category: Neurologic
  name: Hypotonia
  description: Baseline and paroxysmal hypotonia, the latter a defining component of TANGO2 spells.
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  evidence:
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: including sudden onset of hypotonia, ataxia with loss of balance, head and body tilt, increased dysarthria, drooling, lethargy, and disorientation
    explanation: >-
      Names hypotonia within the spell phenotype. Evidence source is OTHER
      because this is a GeneReviews chapter.

- category: Musculoskeletal
  name: Rhabdomyolysis
  description: >-
    Acute skeletal muscle breakdown is the defining somatic manifestation of a
    metabolic crisis, with markedly elevated creatine phosphokinase, transaminase
    elevation, myalgia, weakness and dark urine. It occurred in 15 of the 17
    crisis-affected patients in the French cohort and in more than 70% of
    individuals in a pooled literature review.
  phenotype_term:
    preferred_term: Rhabdomyolysis
    term:
      id: HP:0003201
      label: Rhabdomyolysis
    temporality: RECURRENT
  frequency: FREQUENT
  diagnostic: true
  evidence:
  - reference: PMID:34668327
    reference_title: >-
      Variable clinical severity in TANGO2 deficiency: Case series and literature review.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Common clinical features seen in >70% of all individuals include acute metabolic crisis, rhabdomyolysis, neurologic abnormalities, developmental delay, and intellectual disability.
    explanation: >-
      Pooled review of 92 individuals giving a lower bound above 70%, consistent
      with the FREQUENT band (79-30%). The band is set from this whole-cohort
      figure rather than from the 15/17 crisis-conditional proportion.
  - reference: PMID:32929747
    reference_title: >-
      Clinical and biological characterization of 20 patients with TANGO2 deficiency indicates novel triggers of metabolic crises and no primary energetic defect.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Metabolic crises included rhabdomyolysis (15/17), neurological symptoms (14/17), and cardiac features (12/17; long QT (n = 10), Brugada pattern (n = 2), cardiac arrhythmia (n = 6)) that required intensive care.
    explanation: >-
      Gives the crisis-conditional proportion (15 of 17 patients who had crises).
      Quoted for the composition of a crisis, not as the whole-cohort frequency
      band.

- category: Musculoskeletal
  name: Muscle Weakness
  description: >-
    Weakness is both an acute crisis feature and, at the mild end of the spectrum,
    a chronic limb-girdle pattern with waddling gait and calf pseudohypertrophy
    that can be the presenting phenotype into adulthood.
  phenotype_term:
    preferred_term: Muscle weakness
    term:
      id: HP:0001324
      label: Muscle weakness
  evidence:
  - reference: PMID:37119590
    reference_title: >-
      Limb-girdle myopathy and mild intellectual disability: The expanding spectrum of TANGO2-related disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We report a 40-year-old woman affected by limb-girdle weakness and mild intellectual disability caused by the recurrent deletion of exons 3-9 in homozygosity in the TANGO2 gene.
    explanation: Documents chronic limb-girdle weakness at the mild end of the phenotypic spectrum.

- category: Renal
  name: Myoglobinuria
  description: Dark urine from myoglobin release during rhabdomyolysis, which can precipitate acute kidney injury when severe.
  phenotype_term:
    preferred_term: Myoglobinuria
    term:
      id: HP:0002913
      label: Myoglobinuria
    temporality: ACUTE
  evidence:
  - reference: PMID:39665114
    reference_title: >-
      Complexities of Management of Atypical Ventricular Fibrillation Storm in a Young Patient With TANGO2.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The patient's clinical course was marked by rhabdomyolysis-induced muscle pain, weakness and dark urine.
    explanation: Case-report documentation of myoglobinuric dark urine during a crisis.

- category: Metabolic
  name: Acute Metabolic Crisis with Encephalopathy
  description: >-
    Episodic, catabolic-stress-triggered decompensation combining rhabdomyolysis,
    encephalopathy, hypoglycaemia and lactic acidosis, frequently requiring
    intensive care. In the 73-patient natural-history cohort, 46 of 71 (65%)
    experienced metabolic crises; the 20-patient French series reported a higher
    proportion (17/20), consistent with referral-centre ascertainment.
  phenotype_term:
    preferred_term: Encephalopathy
    term:
      id: HP:0001298
      label: Encephalopathy
    temporality: RECURRENT
  frequency: FREQUENT
  diagnostic: true
  evidence:
  - reference: PMID:36473599
    reference_title: >-
      Natural history of TANGO2 deficiency disorder: Baseline assessment of 73 patients.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: A total of 46/71 (65%) patients suffered metabolic crises, and of those, 30 (65%) developed cardiac crises.
    explanation: >-
      Whole-cohort proportion of 65% (46/71) in the largest natural-history study,
      which falls in the FREQUENT band (79-30%).
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: life-threatening acute metabolic crises can occur, including rhabdomyolysis with elevated creatine phosphokinase and liver transaminases, hypoglycemia, prolonged QTc on EKG, ventricular arrhythmias, and/or cardiomyopathy
    explanation: >-
      Defines the composition of the crisis. Evidence source is OTHER because
      this is a GeneReviews chapter.

- category: Metabolic
  name: Hypoglycemia
  description: Ketotic hypoglycaemia during crises, reflecting failure to sustain fuel supply once glycogen is depleted and fatty-acid oxidation is required.
  phenotype_term:
    preferred_term: Hypoglycemia
    term:
      id: HP:0001943
      label: Hypoglycemia
    temporality: ACUTE
  evidence:
  - reference: PMID:31339582
    reference_title: >-
      Clinical presentation and proteomic signature of patients with TANGO2 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: a distinct clinical and biochemical phenotype of recurrent metabolic crises, hypoglycemia, lactic acidosis, rhabdomyolysis, arrhythmias, and encephalopathy with cognitive decline
    explanation: Places hypoglycaemia within the recognized biochemical crisis phenotype.

- category: Metabolic
  name: Lactic Acidosis
  description: Elevated lactate with metabolic acidosis during crises; lactate is frequently normal between episodes.
  phenotype_term:
    preferred_term: Lactic acidosis
    term:
      id: HP:0003128
      label: Lactic acidosis
    temporality: ACUTE
  evidence:
  - reference: PMID:32909282
    reference_title: >-
      The phenotype associated with variants in TANGO2 may be explained by a dual role of the protein in ER-to-Golgi transport and at the mitochondria.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: recurrent crisis-induced rhabdomyolysis, encephalopathy, seizures, lactic acidosis, hypoglycemia, and cardiac arrhythmias
    explanation: >-
      Names lactic acidosis as a crisis component. Evidence source is OTHER
      because this is the background statement of an in vitro study.
  - reference: PMID:31339582
    reference_title: >-
      Clinical presentation and proteomic signature of patients with TANGO2 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: a distinct clinical and biochemical phenotype of recurrent metabolic crises, hypoglycemia, lactic acidosis, rhabdomyolysis, arrhythmias, and encephalopathy with cognitive decline
    explanation: Primary clinical-series support for lactic acidosis as a crisis finding.

- category: Laboratory
  name: Elevated Creatine Kinase
  description: >-
    Creatine kinase rises steeply during crises and is the principal biochemical
    marker of muscle involvement; unexplained CK elevation should raise suspicion
    for the disorder.
  phenotype_term:
    preferred_term: Elevated circulating creatine kinase concentration
    term:
      id: HP:0003236
      label: Elevated circulating creatine kinase concentration
    temporality: ACUTE
  diagnostic: true
  evidence:
  - reference: PMID:34668327
    reference_title: >-
      Variable clinical severity in TANGO2 deficiency: Case series and literature review.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Findings such as elevated creatine kinase, hypothyroidism, ketotic hypoglycemia, QT prolongation, or abnormalities of long-chain acylcarnitines and urine dicarboxylic acids should raise clinical suspicion for this life-threatening condition.
    explanation: Establishes elevated CK as a diagnostic red flag for TDD.

- category: Cardiovascular
  name: QT Prolongation
  description: >-
    Marked QTc prolongation is the hallmark cardiac abnormality of a TDD cardiac
    crisis. It was present in every one of 27 patients across 43 crisis
    admissions, with a median QTc of 547 ms. A frequency band is deliberately not
    assigned here because the 100% figure is conditional on a cardiac-crisis
    admission and does not describe all diagnosed individuals.
  phenotype_term:
    preferred_term: Prolonged QT interval
    term:
      id: HP:0001657
      label: Prolonged QT interval
    temporality: ACUTE
  diagnostic: true
  context: Measured during a TDD cardiac crisis admission.
  evidence:
  - reference: PMID:35568137
    reference_title: >-
      Cardiac crises: Cardiac arrhythmias and cardiomyopathy during TANGO2 deficiency related metabolic crises.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: During crisis, QTc prolongation occurred in all (median 547 ms; IQR 504-600 ms) and a type I Brugada pattern in 8 (26%).
    explanation: Quantifies universal QTc prolongation and the median value within crisis admissions.

- category: Cardiovascular
  name: Ventricular Tachycardia
  description: >-
    Ventricular tachycardia, including ventricular fibrillation storm, complicates
    cardiac crises and is recalcitrant to standard antiarrhythmic drugs. It
    occurred in 21 of 27 patients (78%) admitted with a cardiac crisis; as with QT
    prolongation, that proportion is conditional on a crisis admission rather than
    a whole-cohort frequency, so no frequency band is assigned.
  phenotype_term:
    preferred_term: Ventricular tachycardia
    term:
      id: HP:0004756
      label: Ventricular tachycardia
    temporality: ACUTE
  context: Measured during a TDD cardiac crisis admission.
  evidence:
  - reference: PMID:35568137
    reference_title: >-
      Cardiac crises: Cardiac arrhythmias and cardiomyopathy during TANGO2 deficiency related metabolic crises.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Arrhythmias included VT in 21 (78%), supraventricular tachycardia in 3 (11%), and heart block in 1 (4%).
    explanation: Gives the ventricular tachycardia proportion within cardiac-crisis admissions.
  - reference: PMID:38855866
    reference_title: >-
      Folate as a potential treatment for lethal ventricular arrhythmias in TANGO2-deficiency disorder.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: TDD-associated cardiac arrhythmias are recalcitrant to standard antiarrhythmic medications and constitute the leading cause of death.
    explanation: >-
      Establishes drug refractoriness and mortality significance. Evidence source
      is OTHER because this is the framing statement of an iPSC-cardiomyocyte
      study rather than its own clinical result.

- category: Cardiovascular
  name: Torsade de Pointes
  description: Polymorphic ventricular tachycardia arising on the prolonged-QT substrate during crises.
  phenotype_term:
    preferred_term: Torsade de pointes
    term:
      id: HP:0001664
      label: Torsade de pointes
    temporality: ACUTE
  evidence:
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: continuous rhythm monitoring for arrhythmias including premature ventricular contractions, ventricular tachycardia, and torsade de pointes
    explanation: >-
      Recorded as PARTIAL because this is a surveillance recommendation naming
      torsade de pointes as an arrhythmia to watch for, rather than a report of
      its observed frequency. Evidence source is OTHER because this is a
      GeneReviews chapter.

- category: Cardiovascular
  name: Cardiac Arrest
  description: >-
    Cardiac arrest occurred in 20 of 27 patients (74%) admitted with a TDD cardiac
    crisis, and arrhythmia accounted for 6 of the 10 deaths in that series.
  phenotype_term:
    preferred_term: Cardiac arrest
    term:
      id: HP:0001695
      label: Cardiac arrest
    temporality: ACUTE
  context: Measured during a TDD cardiac crisis admission.
  evidence:
  - reference: PMID:35568137
    reference_title: >-
      Cardiac crises: Cardiac arrhythmias and cardiomyopathy during TANGO2 deficiency related metabolic crises.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Nineteen patients (70%) developed cardiomyopathy, and 20 (74%) experienced a cardiac arrest. There were 10 deaths (37%), 6 related to arrhythmias.
    explanation: Quantifies cardiac arrest and arrhythmia-attributable mortality within crisis admissions.

- category: Cardiovascular
  name: Cardiomyopathy
  description: >-
    Crisis-associated ventricular dysfunction developed in 19 of 27 patients (70%)
    admitted with a cardiac crisis. It is often reversible with recovery from the
    crisis, but severe cases have required ECMO support.
  phenotype_term:
    preferred_term: Cardiomyopathy
    term:
      id: HP:0001638
      label: Cardiomyopathy
    temporality: ACUTE
  context: Measured during a TDD cardiac crisis admission.
  evidence:
  - reference: PMID:35568137
    reference_title: >-
      Cardiac crises: Cardiac arrhythmias and cardiomyopathy during TANGO2 deficiency related metabolic crises.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Nineteen patients (70%) developed cardiomyopathy, and 20 (74%) experienced a cardiac arrest.
    explanation: Quantifies crisis-associated cardiomyopathy.

- category: Endocrine
  name: Hypothyroidism
  description: >-
    Hypothyroidism, often with isolated TSH elevation, was present in 12 of 20
    patients (60%) in the French cohort and is readily treatable with
    levothyroxine, making thyroid surveillance a standard part of care.
  phenotype_term:
    preferred_term: Hypothyroidism
    term:
      id: HP:0000821
      label: Hypothyroidism
    temporality: CHRONIC
  frequency: FREQUENT
  evidence:
  - reference: PMID:32929747
    reference_title: >-
      Clinical and biological characterization of 20 patients with TANGO2 deficiency indicates novel triggers of metabolic crises and no primary energetic defect.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Here, we describe a cohort of 20 French patients bearing mutations in the TANGO2 gene. We found that the main clinical presentation was the association of neurodevelopmental delay (n = 17), acute metabolic crises (n = 17) and hypothyroidism (n = 12), with a large intrafamilial clinical variability.
    explanation: >-
      Gives numerator and denominator (12/20 = 60%), which falls in the FREQUENT
      band (79-30%).

- category: Gastrointestinal
  name: Feeding Difficulties
  description: >-
    Feeding and swallowing difficulty is common and functionally important, at
    times requiring feeding therapy or gastrostomy tube placement.
  phenotype_term:
    preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
    temporality: CHRONIC
  evidence:
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: feeding therapy and/or gastrostomy tube feeding as needed
    explanation: >-
      Recorded as PARTIAL because this is a management recommendation implying
      feeding difficulty rather than a direct report of the phenotype or its
      frequency. Evidence source is OTHER because this is a GeneReviews chapter.

genetic:
- name: TANGO2
  gene_term:
    preferred_term: TANGO2
    term:
      id: hgnc:25439
      label: TANGO2
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  association: >-
    Biallelic loss-of-function variants in TANGO2 at 22q11.21 are necessary and
    sufficient to cause TANGO2 deficiency disorder. Reported pathogenic classes
    include multiexon deletions, nonsense, frameshift, canonical splice-site,
    small in-frame deletion and missense variants. The recurrent 34-kb deletion of
    exons 3-9 is the single most common allele, seen in 42% of reported
    individuals and enriched in European-ancestry cases; c.460G>A (p.Gly154Arg) is
    recurrent in Hispanic/Latino families. Because the disorder is caused by
    deletions as often as by sequence variants, exon-level deletion/duplication
    analysis is required alongside sequencing, and hemizygous variants that appear
    heterozygous on sequencing alone are a recognized diagnostic pitfall.
  evidence:
  - reference: PMID:26805782
    reference_title: >-
      Bi-allelic Truncating Mutations in TANGO2 Cause Infancy-Onset Recurrent Metabolic Crises with Encephalocardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Our results establish TANGO2 deficiency as a clinically recognizable cause of pediatric disease with multi-organ involvement.
    explanation: The gene-disease relationship as first established.
  - reference: PMID:34668327
    reference_title: >-
      Variable clinical severity in TANGO2 deficiency: Case series and literature review.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Of the 27 pathogenic variants reported to date, the recurrent exons 3-9 deletion represents the most common variant seen in 42% of individuals with TANGO2 deficiency.
    explanation: Quantifies the dominance of the recurrent exon 3-9 deletion in the reported allelic spectrum.
  - reference: PMID:31339582
    reference_title: >-
      Clinical presentation and proteomic signature of patients with TANGO2 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The other subjects carried three novel homozygous (c.262C>T/p.Arg88*; c.220A>C/p.Thr74Pro; c.380+1G>A), and two further novel heterozygous
    explanation: Illustrates the nonsense, missense and splice-site variant classes contributing to the allelic spectrum.
  - reference: PMID:31339582
    reference_title: >-
      Clinical presentation and proteomic signature of patients with TANGO2 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The hemizygous mutations in two patients suggest that some mutations leading to allele loss are difficult to detect.
    explanation: Supports the diagnostic pitfall of apparently heterozygous variants that are in fact hemizygous.
  - reference: PMID:30245509
    reference_title: >-
      TANGO2: expanding the clinical phenotype and spectrum of pathogenic variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the need for additional copy-number variation analysis when ES is performed
    explanation: Supports the requirement for copy-number analysis alongside exome sequencing.
  - reference: PMID:36473599
    reference_title: >-
      Natural history of TANGO2 deficiency disorder: Baseline assessment of 73 patients.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: A total of 24 different TANGO2 alleles were observed.
    explanation: Quantifies allelic heterogeneity across the 73-patient natural-history cohort.

- name: TANGO2 unmasked by a 22q11.2 deletion in trans
  gene_term:
    preferred_term: TANGO2
    term:
      id: hgnc:25439
      label: TANGO2
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  association: >-
    TANGO2 lies within the interval recurrently deleted in 22q11.2 deletion
    syndrome. An individual carrying a 22q11.2 deletion that removes one TANGO2
    allele develops TDD if the remaining allele carries a pathogenic sequence
    variant - an autosomal-recessive second diagnosis unmasked by the deletion.
    This configuration has been documented directly, and it makes 22q11.2 deletion
    syndrome an at-risk group in which TDD is thought to be underdiagnosed because
    the phenotypes overlap. A multicentre screen of 435 individuals with 22q11.2
    deletion syndrome identified 21 meeting consensus criteria for TANGO2 testing;
    of the nine actually sequenced with deletion/duplication analysis, none were
    diagnosed with TDD, so the practical yield of symptom-based screening remains
    unproven. This entry describes the TDD side of that relationship; the
    22q11.2 Deletion Syndrome entry covers it as a second-diagnosis and
    differential-diagnosis consideration.
  evidence:
  - reference: PMID:38829177
    reference_title: >-
      Multicenter appraisal of comorbid TANGO2 deficiency disorder in patients with 22q11.2 deletion syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: TANGO2 deficiency disorder (TDD) is a rare, autosomal recessive condition caused by pathogenic variants in TANGO2, a gene residing within the region commonly deleted in 22q11.2 deletion syndrome (22q11.2DS).
    explanation: Establishes that TANGO2 lies within the 22q11.2 deleted interval.
  - reference: PMID:38829177
    reference_title: >-
      Multicenter appraisal of comorbid TANGO2 deficiency disorder in patients with 22q11.2 deletion syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Although patients with 22q11.2DS are at substantially higher risk for comorbid TDD, it remains underdiagnosed within 22q11.2DS, likely due to overlapping symptomatology and a lack of knowledge about TDD.
    explanation: Supports the elevated risk and the underdiagnosis concern in this group.
  - reference: PMID:38829177
    reference_title: >-
      Multicenter appraisal of comorbid TANGO2 deficiency disorder in patients with 22q11.2 deletion syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Of the nine patients undergoing TANGO2 sequencing with del/dup analysis, none were ultimately diagnosed with TDD.
    explanation: >-
      Recorded as PARTIAL: the null yield constrains how strongly symptom-based
      screening can be recommended, while the study's own conclusion is that
      better prospective screening tools are needed rather than that screening is
      unwarranted.
  - reference: PMID:31339582
    reference_title: >-
      Clinical presentation and proteomic signature of patients with TANGO2 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Two carried the reported deletion of exons 3 to 9, one homozygous, one heterozygous with a 22q11.21 microdeletion inherited in trans.
    explanation: A directly documented instance of biallelic TANGO2 loss produced by a sequence-level deletion plus a 22q11.21 microdeletion in trans.
  - reference: PMID:42420940
    reference_title: >-
      TANGO2-related metabolic encephalopathy-arrhythmia syndrome unmasked in 22q11.2 deletion syndrome: hemizygous pathogenic variant, complex phenotype modified by two genetic conditions, and implications for proactive crisis prevention: a case report.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Patients with 22q11.2 deletion syndrome are at increased risk when a pathogenic variant occurs in the remaining allele, yet this dual diagnosis remains underrecognized as clinicians often attribute all manifestations to the primary genetic condition.
    explanation: >-
      The dedicated case report of TDD unmasked by a 22q11.2 deletion; this is the
      same source the 22q11.2 Deletion Syndrome entry uses for the reciprocal
      claim, keeping the two entries consistent.

inheritance:
- name: Autosomal recessive inheritance
  description: >-
    TDD is inherited in an autosomal recessive manner. Parents of an affected
    child are typically heterozygous carriers, giving a 25% recurrence risk per
    pregnancy. Penetrance for biallelic severe loss of function appears high, but
    expressivity is markedly variable - including between siblings who share a
    genotype - so genotype does not reliably predict severity. Consanguinity
    increases the chance of homozygosity but is not required; compound
    heterozygosity and unmasking by a 22q11.2 deletion in trans are both
    recognized routes to biallelic loss.
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:38829177
    reference_title: >-
      Multicenter appraisal of comorbid TANGO2 deficiency disorder in patients with 22q11.2 deletion syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: TANGO2 deficiency disorder (TDD) is a rare, autosomal recessive condition caused by pathogenic variants in TANGO2
    explanation: States the mode of inheritance.
  - reference: PMID:31339582
    reference_title: >-
      Clinical presentation and proteomic signature of patients with TANGO2 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: All nine subjects carried autosomal recessive TANGO2 mutations.
    explanation: Confirms recessive segregation across an independent multi-family series.
  - reference: PMID:42115085
    reference_title: >-
      Molecular basis and clinical implications of TANGO2 deficiency disorder.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Intrafamilial phenotypic variability and overlapping manifestations with other metabolic diseases complicate timely and accurate diagnosis.
    explanation: >-
      Supports the variable-expressivity statement. Evidence source is OTHER
      because this is a review article.
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: If both parents are known to be heterozygous for a TANGO2 pathogenic variant, each sib of an affected individual has at conception a 25% chance of being affected, a 50% chance of being a carrier, and a 25% chance of inheriting neither of the familial pathogenic variants.
    explanation: >-
      Sources the 25% recurrence risk and carrier probabilities stated in this
      block. Evidence source is OTHER because this is a GeneReviews chapter.

environmental:
- name: Catabolic stress
  influences_mechanisms:
  - target: Catabolic Stress Exposure
    environmental_effect: TRIGGERS
    causal_link_type: DIRECT
    description: >-
      The node is named for this exposure and describes the disorder as
      stress-unmasked: the genotype is present from conception and the acute
      phenotype requires an extrinsic catabolic challenge. Exposure and node
      are therefore the same thing, and the cited chapter enumerates the
      precipitants the node lists.
    evidence:
    - reference: PMID:29369572
      reference_title: "TANGO2 Deficiency."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "Triggers for TANGO2 spells and acute metabolic crises including fasting, dehydration, overexertion, exposure to excessive heat, ketogenic diet, and infections."
      explanation: >-
        Enumerates fasting, dehydration, overexertion, excessive heat,
        ketogenic diet and infection as triggers, which is this node's own
        content.
  description: >-
    Fever and intercurrent illness, fasting, dehydration, reduced oral intake,
    excessive heat, overexertion and a ketogenic diet precipitate metabolic
    crises and TANGO2 spells. These are not causes of the disorder but the
    modifiable determinants of when and how severely it manifests, which is why
    avoidance of catabolism is the backbone of preventive care.
  evidence:
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Triggers for TANGO2 spells and acute metabolic crises including fasting, dehydration, overexertion, exposure to excessive heat, ketogenic diet, and infections.
    explanation: >-
      Enumerates the crisis triggers. Evidence source is OTHER because this is a
      GeneReviews chapter.

- name: Anaesthetic exposure
  exposure_term:
    preferred_term: exposure to anaesthetic
    term:
      id: ECTO:9001793
      label: exposure to anaesthetic
  influences_mechanisms:
  - target: Catabolic-Stress Metabolic Decompensation
    environmental_effect: TRIGGERS
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Pointed at the crisis rather than at the catabolic stress node, because
      an anaesthetic is not obviously a catabolic challenge and the node
      upstream is defined by catabolism; that is a real gap in the graph and
      is better stated than papered over. Graded partial throughout because
      the authors hedge the finding themselves and identify neither the
      responsible agents nor a mechanism, which is also why the practical
      recommendation is perioperative planning rather than a blanket
      contraindication.
    evidence:
    - reference: PMID:32929747
      reference_title: "Clinical and biological characterization of 20 patients with TANGO2 deficiency indicates novel triggers of metabolic crises and no primary energetic defect."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We show previously uncharacterized triggers of metabolic crises in TANGO2 patients, such as some anesthetics and possibly l-carnitine."
      explanation: >-
        Reports previously uncharacterised triggers of metabolic crises
        including some anaesthetics. The crisis is this node, but the sentence
        names no agent and offers no route to it.
  description: >-
    Certain anaesthetic agents were identified as previously uncharacterized
    triggers of metabolic crises in a 20-patient cohort. This warrants
    multidisciplinary perioperative planning involving metabolic, anaesthetic and
    cardiology teams rather than a blanket contraindication, since the specific
    agents and mechanism are not established.
  evidence:
  - reference: PMID:32929747
    reference_title: >-
      Clinical and biological characterization of 20 patients with TANGO2 deficiency indicates novel triggers of metabolic crises and no primary energetic defect.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We show previously uncharacterized triggers of metabolic crises in TANGO2 patients, such as some anesthetics and possibly l-carnitine.
    explanation: >-
      Recorded as PARTIAL because the authors themselves hedge the finding
      ("possibly") and do not identify the responsible agents or mechanism.

treatments:
- name: Daily B-Complex or Multivitamin Supplementation
  description: >-
    Daily supplementation with a multivitamin containing all eight B vitamins, or
    a B-complex preparation, is the principal disease-directed intervention and is
    recommended in expert-consensus guidance. The evidence base is convergent but
    not randomized: in the 73-patient natural-history study metabolic crises were
    significantly reduced after supplementation was started, and an independent
    natural-history analysis found that multivitamin/B-complex intake greatly
    diminished the risk of cardiac crises. Both observations are retrospective and
    uncontrolled. No randomized controlled trial has been performed, optimal dose
    and formulation are not standardized, and the long-term safety of sustained
    high-dose supplementation in children (including vitamin B6 toxicity, for
    which serum monitoring is advised) is explicitly flagged as unresolved. This
    is therefore curated as a promising, guideline-endorsed but trial-unvalidated
    intervention rather than as proven standard of care.
  treatment_term:
    preferred_term: nutritional supplementation
    term:
      id: NCIT:C15433
      label: Nutritional Support
    therapeutic_agent:
    - preferred_term: pantothenate (vitamin B5)
      term:
        id: CHEBI:29032
        label: (R)-pantothenate
    - preferred_term: folic acid (vitamin B9)
      term:
        id: CHEBI:27470
        label: folic acid
  therapeutic_modality: SMALL_MOLECULE
  target_mechanisms:
  - target: Lipid and Acyl-CoA Homeostasis Failure
    treatment_effect: RESTORES
    description: >-
      Pantothenate is the biosynthetic precursor of coenzyme A; restoring the CoA
      precursor pool is the proposed route by which B5 reverses the acyl-CoA and
      lipid imbalance.
  target_phenotypes:
  - preferred_term: Encephalopathy
    term:
      id: HP:0001298
      label: Encephalopathy
  - preferred_term: Ventricular tachycardia
    term:
      id: HP:0004756
      label: Ventricular tachycardia
  evidence:
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Daily supplementation with a multivitamin including all eight B vitamins or a B-complex vitamin at the minimum recommended daily allowance for age.
    explanation: >-
      The expert-consensus targeted-therapy recommendation. Evidence source is
      OTHER because this is a GeneReviews chapter, not a trial.
  - reference: PMID:36473599
    reference_title: >-
      Natural history of TANGO2 deficiency disorder: Baseline assessment of 73 patients.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Metabolic crises were significantly decreased after the initiation of B-complex or multivitamin supplementation.
    explanation: The primary observational human signal, from the 73-patient natural-history cohort.
  - reference: PMID:36473599
    reference_title: >-
      Natural history of TANGO2 deficiency disorder: Baseline assessment of 73 patients.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We provide the most comprehensive review of natural history of TDD and important observational data suggesting that B-complex or multivitamins may prevent metabolic crises.
    explanation: >-
      Recorded as PARTIAL because the authors frame their own result as
      observational and hedged ("suggesting", "may prevent"), which is the
      epistemic level at which this treatment should be curated.
  - reference: PMID:38855866
    reference_title: >-
      Folate as a potential treatment for lethal ventricular arrhythmias in TANGO2-deficiency disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Our natural history study in patients with TDD suggests that the intake of multivitamin/B complex greatly diminished the risk of cardiac crises in patients with TDD.
    explanation: >-
      Observational support for the cardiac-crisis endpoint specifically.
      Recorded as PARTIAL because the source hedges ("suggests") and because the
      natural history study referred to is the same Baylor cohort reported in
      PMID:36473599, so this is a restatement rather than an independent cohort.
  - reference: PMID:38836374
    reference_title: >-
      TANGO2 deficiency disease is predominantly caused by a lipid imbalance.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: much remains unknown about TANGO2 function, the pathological mechanism of TDD and the possible downsides of sustained vitamin supplementation in children and young adults
    explanation: >-
      Records the explicit safety and evidence caveat from a Perspective article,
      constraining how strongly this treatment can be asserted.
  - reference: PMID:42196371
    reference_title: >-
      Genetic and Clinical Characterization of TANGO2 Deficiency Disorder: Insights from the Italian Multicentre Cohort.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Early supplementation therapy may contribute to clinical stability, though prospective controlled studies are needed.
    explanation: A recent multicentre cohort reaching the same hedged conclusion and explicitly calling for controlled trials.
  - reference: PMID:37381587
    reference_title: >-
      Management of acute metabolic crisis in TANGO2 deficiency: a case report.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Vitamin B-complex was started. Our patient's mental status and rhabdomyolysis improved dramatically, and cardiac crises ended without Torsades de pointes, ventricular tachycardia and/or fibrillation or myocardial dysfunction.
    explanation: >-
      A single uncontrolled case of B-complex use during an acute crisis;
      recorded as PARTIAL because temporal improvement in one patient cannot be
      separated from the natural resolution of a crisis under supportive care.

- name: Vitamin B5 (Pantothenate)
  description: >-
    Pantothenate, the coenzyme A precursor, is the best-characterized single
    active component of B-complex therapy in model systems. It improves multiple
    TANGO2 loss-of-function defects in Drosophila, rescues membrane-trafficking
    defects in human cells, reverses the lipid-profile abnormalities of
    TANGO2-deficient human cells and flies, and alleviates motor deficits and
    cerebellar myelin loss in Tango2 knockout mice. Human evidence is limited to
    single-patient reports of symptomatic improvement on B5 monotherapy; it is not
    established as a standalone therapy.
  treatment_term:
    preferred_term: nutritional supplementation
    term:
      id: NCIT:C15433
      label: Nutritional Support
    therapeutic_agent:
    - preferred_term: pantothenate (vitamin B5)
      term:
        id: CHEBI:29032
        label: (R)-pantothenate
  therapeutic_modality: SMALL_MOLECULE
  target_mechanisms:
  - target: Lipid and Acyl-CoA Homeostasis Failure
    treatment_effect: RESTORES
    description: Restores the coenzyme A precursor pool needed for acyl-CoA-dependent lipid acylation.
  evidence:
  - reference: PMID:36502486
    reference_title: >-
      Vitamin B5, a coenzyme A precursor, rescues TANGO2 deficiency disease-associated defects in Drosophila and human cells.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: We demonstrate that vitamin B5 specifically improves multiple defects associated with TANGO2 loss-of-function in Drosophila
    explanation: The primary in vivo rescue result in the Drosophila model.
  - reference: PMID:36502486
    reference_title: >-
      Vitamin B5, a coenzyme A precursor, rescues TANGO2 deficiency disease-associated defects in Drosophila and human cells.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: and rescues membrane trafficking defects in human cells
    explanation: The parallel rescue of the ER-to-Golgi trafficking defect in human TANGO2-deficient cells.
  - reference: PMID:36502486
    reference_title: >-
      Vitamin B5, a coenzyme A precursor, rescues TANGO2 deficiency disease-associated defects in Drosophila and human cells.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Our data suggest that a B complex supplement containing vitamin B5/pantothenate may have therapeutic benefits in individuals with TANGO2-deficiency disease.
    explanation: >-
      Recorded as PARTIAL because the translational claim is the authors' hedged
      extrapolation from model systems, not a human result.
  - reference: PMID:42522778
    reference_title: >-
      Oligodendroglial TANGO2 Regulates Lipid Metabolism to Control Motor Coordination.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Significantly, vitamin B5 supplementation alleviated motor deficits and cerebellar myelin defects in Tango2 knockout mice.
    explanation: Extends B5 rescue to a mammalian model and to the chronic neurological phenotype.
  - reference: PMID:39641377
    reference_title: >-
      Vitamin B5 Monotherapy Improves Symptoms in a 7-Year-Old Girl With TANGO2 Deficiency Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: This report highlights the potential therapeutic effects of vitamin B5 against this disease and suggests that high-dose vitamin B5 administration may be safe for the treatment of TANGO2 deficiency disorder.
    explanation: >-
      A single-patient report; recorded as PARTIAL because an n=1 uncontrolled
      observation cannot establish efficacy or safety.

- name: Folate (Vitamin B9) for Arrhythmia Prevention
  description: >-
    High-dose folate virtually abolishes arrhythmias in patient-derived
    TANGO2-null iPSC cardiomyocytes, and the effect is blocked by methotrexate,
    indicating a requirement for intracellular folate metabolism. Combined B5 plus
    B9 pretreatment prevents the palmitate-and-fasting-induced energetic crisis in
    an independent CRISPR cardiomyocyte model. Human evidence is observational
    only; folate is not established as a standalone antiarrhythmic in TDD and is
    delivered in practice as part of B-complex supplementation.
  treatment_term:
    preferred_term: nutritional supplementation
    term:
      id: NCIT:C15433
      label: Nutritional Support
    therapeutic_agent:
    - preferred_term: folic acid (vitamin B9)
      term:
        id: CHEBI:27470
        label: folic acid
  therapeutic_modality: SMALL_MOLECULE
  target_mechanisms:
  - target: Cardiomyocyte ATP Depletion and Repolarization Instability
    treatment_effect: INHIBITS
    description: Prevents the energy-dependent action-potential prolongation that underlies TDD arrhythmia.
  target_phenotypes:
  - preferred_term: Ventricular tachycardia
    term:
      id: HP:0004756
      label: Ventricular tachycardia
  evidence:
  - reference: PMID:38855866
    reference_title: >-
      Folate as a potential treatment for lethal ventricular arrhythmias in TANGO2-deficiency disorder.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: we demonstrated that high-dose folate (vitamin B9) virtually abolishes arrhythmias in TDD iPSC-CMs and that folate's effect was blocked by the dihydrofolate reductase inhibitor methotrexate, supporting the need for intracellular folate to mediate antiarrhythmic effects
    explanation: The primary in vitro antiarrhythmic result and its mechanistic control.
  - reference: PMID:42389941
    reference_title: >-
      Metabolic crisis and TRPM4 activation cause QT prolongation in TANGO2 deficiency disorder.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: This crisis was prevented by 2-week treatment with vitamins B5 and B9.
    explanation: Independent CRISPR cardiomyocyte model showing combined B5/B9 pretreatment prevents the energetic crisis.

- name: Acute Crisis Management with Dextrose-Containing Fluids and Nutrition
  description: >-
    During an acute crisis, admission for intravenous hydration with
    glucose-containing fluids, correction of hypoglycaemia, and prompt restoration
    of full enteral or parenteral nutrition including vitamin supplementation is
    the mainstay. Fluid rate must be adjusted against echocardiographic assessment
    of cardiac function to avoid pulmonary oedema. Glucose alone appears
    insufficient: initiation of feeds was associated with a reduction in
    ventricular tachycardia events, suggesting complete nutrition rather than
    dextrose alone is what matters.
  treatment_term:
    preferred_term: fluid replacement therapy
    term:
      id: NCIT:C66896
      label: Hydration Therapy
    therapeutic_agent:
    - preferred_term: glucose
      term:
        id: CHEBI:17234
        label: glucose
  target_mechanisms:
  - target: Catabolic-Stress Metabolic Decompensation
    treatment_effect: INHIBITS
    description: Reverses the catabolic state driving the crisis by restoring exogenous fuel supply.
  evidence:
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: intravenous (IV) hydration with glucose-containing fluids for hypoglycemia; echocardiogram to assess cardiac function with adjustment of IV fluids to prevent pulmonary edema
    explanation: >-
      The consensus acute-management protocol including the fluid-titration
      caveat. Evidence source is OTHER because this is a GeneReviews chapter.
  - reference: PMID:35568137
    reference_title: >-
      Cardiac crises: Cardiac arrhythmias and cardiomyopathy during TANGO2 deficiency related metabolic crises.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Initiation of feeds seemed to decrease VT events.
    explanation: >-
      Recorded as PARTIAL because this is a hedged retrospective observation
      ("seemed to") rather than a controlled comparison.

- name: Acute Antiarrhythmic Management
  description: >-
    TDD crisis arrhythmias respond poorly to standard antiarrhythmic drugs.
    Reported effective measures are intravenous magnesium (with magnesium
    maintained above 2.2 mg/dL), isoproterenol, atrial overdrive pacing, and
    aggressive electrolyte correction; verapamil was effective in one patient and
    has independent mechanistic support from L-type calcium channel inhibition in
    the cardiomyocyte model. Management by an electrophysiologist is recommended
    rather than application of generic long-QT algorithms.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: magnesium sulfate
      term:
        id: CHEBI:32599
        label: magnesium sulfate
    - preferred_term: isoproterenol
      term:
        id: CHEBI:64317
        label: isoprenaline
    - preferred_term: verapamil
      term:
        id: CHEBI:9948
        label: verapamil
  therapeutic_modality: SMALL_MOLECULE
  target_mechanisms:
  - target: Arrhythmogenic Substrate and Triggered Activity
    treatment_effect: INHIBITS
    description: Magnesium, rate support and calcium-channel blockade act to suppress triggered activity on the prolonged-repolarization substrate.
  target_phenotypes:
  - preferred_term: Ventricular tachycardia
    term:
      id: HP:0004756
      label: Ventricular tachycardia
  evidence:
  - reference: PMID:35568137
    reference_title: >-
      Cardiac crises: Cardiac arrhythmias and cardiomyopathy during TANGO2 deficiency related metabolic crises.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Among 10 patients who survived VT without ECMO, successful treatment included intravenous magnesium, isoproterenol, and atrial pacing in multiple cases and verapamil in 1 patient.
    explanation: The primary clinical evidence for the specific agents used successfully during TDD arrhythmia.
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: supplemental magnesium to maintain magnesium >2.2 mg/dL to minimize arrhythmias
    explanation: >-
      Sources the specific magnesium target stated in this treatment. Evidence
      source is OTHER because this is a GeneReviews chapter.
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Due to the recalcitrant nature of ventricular arrhythmias, management by an electrophysiologist is recommended.
    explanation: >-
      Supports specialist-directed management. Evidence source is OTHER because
      this is a GeneReviews chapter.
  - reference: PMID:42389941
    reference_title: >-
      Metabolic crisis and TRPM4 activation cause QT prolongation in TANGO2 deficiency disorder.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: LTCC inhibition with verapamil prevented AP prolongation by normalizing ATP/ADP ratios and intracellular Ca mishandling.
    explanation: Mechanistic rationale for the verapamil observation, from the CRISPR cardiomyocyte model.

- name: Extracorporeal Membrane Oxygenation for Refractory Arrhythmia
  description: >-
    ECMO is used as a last-resort rescue for arrhythmia or cardiogenic shock
    refractory to medical therapy. In the 27-patient cardiac-crisis series,
    arrhythmias were controlled after ECMO in 6 patients, 5 of whom survived. In a
    single reported case, thoracoscopic left sympathectomy performed during ECMO
    support terminated a refractory ventricular fibrillation storm.
  treatment_term:
    preferred_term: extracorporeal membrane oxygenation
    term:
      id: NCIT:C171507
      label: Extracorporeal Membrane Oxygenation
  therapeutic_modality: DEVICE
  target_phenotypes:
  - preferred_term: Cardiac arrest
    term:
      id: HP:0001695
      label: Cardiac arrest
  evidence:
  - reference: PMID:35568137
    reference_title: >-
      Cardiac crises: Cardiac arrhythmias and cardiomyopathy during TANGO2 deficiency related metabolic crises.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In 6 patients, arrhythmias were controlled after extracorporeal membrane oxygenation (ECMO) support; 5 of these patients survived.
    explanation: Quantifies ECMO outcomes in refractory TDD arrhythmia.
  - reference: PMID:39665114
    reference_title: >-
      Complexities of Management of Atypical Ventricular Fibrillation Storm in a Young Patient With TANGO2.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In a life-saving therapeutic approach, the patient underwent a thoracoscopic left sympathectomy during extracorporeal membrane oxygenation (ECMO) support. Remarkably, this intervention resulted in the termination of the ventricular arrhythmia storm.
    explanation: >-
      Recorded as PARTIAL because sympathectomy during ECMO is described in a
      single case report and is not an established TDD intervention.

- name: Avoidance of Catabolic Triggers and Sick-Day Planning
  description: >-
    Preventive care centres on avoiding prolonged fasting and dehydration,
    maintaining regular meals, avoiding a ketogenic diet, limiting exertion and
    heat exposure during illness, and having a written sick-day plan with early
    hospital evaluation for fever, reduced intake, weakness, dark urine, seizure
    or palpitations.
  treatment_term:
    preferred_term: dietary intervention
    term:
      id: NCIT:C15447
      label: Dietary Intervention
  therapeutic_modality: BEHAVIORAL
  target_mechanisms:
  - target: Catabolic Stress Exposure
    treatment_effect: INHIBITS
    description: Removes or blunts the extrinsic trigger required to convert the latent genotype into an acute crisis.
  evidence:
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Agents/circumstances to avoid: Triggers for TANGO2 spells and acute metabolic crises including fasting, dehydration, overexertion, exposure to excessive heat, ketogenic diet, and infections."
    explanation: >-
      The consensus avoidance recommendation. Evidence source is OTHER because
      this is a GeneReviews chapter.

- name: Levothyroxine for Hypothyroidism
  description: >-
    Hypothyroidism is common and treatable; levothyroxine is given as needed, with
    annual TSH and free T4 surveillance.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: levothyroxine
      term:
        id: CHEBI:18332
        label: L-thyroxine
  therapeutic_modality: SMALL_MOLECULE
  target_phenotypes:
  - preferred_term: Hypothyroidism
    term:
      id: HP:0000821
      label: Hypothyroidism
  evidence:
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: levothyroxine as needed for hypothyroidism
    explanation: >-
      The consensus treatment for the endocrine manifestation. Evidence source is
      OTHER because this is a GeneReviews chapter.

- name: Cardiac Surveillance
  description: >-
    Serial ECG for QTc and for emergence of a type 1 Brugada pattern, continuous
    rhythm monitoring during illness, and echocardiography at a frequency guided
    by the individual's history of metabolic and cardiac crises.
  treatment_term:
    preferred_term: electrocardiography
    term:
      id: NCIT:C38053
      label: Electrocardiography
  target_phenotypes:
  - preferred_term: Prolonged QT interval
    term:
      id: HP:0001657
      label: Prolonged QT interval
  evidence:
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: EKG to monitor QTc and for development of type 1 Brugada pattern; continuous rhythm monitoring for arrhythmias including premature ventricular contractions, ventricular tachycardia, and torsade de pointes
    explanation: >-
      The consensus cardiac surveillance protocol. Evidence source is OTHER
      because this is a GeneReviews chapter.

- name: Genetic Counseling
  description: >-
    Counselling should cover autosomal-recessive recurrence risk (25% per
    pregnancy when both parents are carriers), marked variable expressivity that
    limits genotype-based prognosis, the requirement to test for deletions as
    well as sequence variants, the availability of carrier, prenatal and
    preimplantation testing once the familial variants are known, and cascade
    testing of apparently asymptomatic siblings so that B-complex vitamins,
    supportive treatment and trigger avoidance can be started before a first
    crisis.
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  therapeutic_modality: BEHAVIORAL
  evidence:
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: If both parents are known to be heterozygous for a TANGO2 pathogenic variant, each sib of an affected individual has at conception a 25% chance of being affected, a 50% chance of being a carrier, and a 25% chance of inheriting neither of the familial pathogenic variants.
    explanation: >-
      Sources the autosomal-recessive recurrence-risk counselling content.
      Evidence source is OTHER because this is a GeneReviews chapter.
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Once the TANGO2 pathogenic variants have been identified in an affected family member, carrier testing for at-risk relatives and prenatal/preimplantation genetic testing are possible.
    explanation: >-
      Sources the carrier-testing, prenatal and preimplantation testing options.
      Evidence source is OTHER because this is a GeneReviews chapter.
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: It is appropriate to clarify the genetic status of apparently asymptomatic older and younger sibs of an affected individual by molecular genetic testing to allow prompt initiation of B-complex vitamins, supportive treatment, and avoidance of triggers for TANGO2 spells and acute metabolic crises.
    explanation: >-
      Sources cascade testing of at-risk siblings and the actionable reason for
      it. Evidence source is OTHER because this is a GeneReviews chapter.
  - reference: PMID:42196371
    reference_title: >-
      Genetic and Clinical Characterization of TANGO2 Deficiency Disorder: Insights from the Italian Multicentre Cohort.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: This cohort expands the mutational and phenotypic spectrum of TDD and highlights the diagnostic value of TANGO2 testing in patients with neurodevelopmental delay or paroxysmal neurological episodes, even in the absence of metabolic crises.
    explanation: Supports the counselling point that testing is warranted on the neurological phenotype alone.

diagnosis:
- name: Molecular genetic testing with deletion/duplication analysis
  description: >-
    Diagnosis is established by identifying biallelic pathogenic TANGO2 variants.
    Because multiexon deletions account for a large share of pathogenic alleles,
    testing must combine sequence analysis with exon-level deletion/duplication
    analysis; exome sequencing alone requires additional copy-number analysis. In
    an individual with a 22q11.2 deletion and suggestive features, the remaining
    TANGO2 allele should be sequenced.
  diagnosis_term:
    preferred_term: genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: The diagnosis of TANGO2 deficiency is established in a proband with biallelic pathogenic variants in TANGO2 identified by molecular genetic testing.
    explanation: >-
      States the diagnostic standard. Evidence source is OTHER because this is a
      GeneReviews chapter.
  - reference: PMID:30245509
    reference_title: >-
      TANGO2: expanding the clinical phenotype and spectrum of pathogenic variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We illustrate the utility of routine ES data reanalysis whereby discovery of novel disease genes can lead to a diagnosis in previously unsolved cases and the need for additional copy-number variation analysis when ES is performed.
    explanation: Supports the requirement for copy-number analysis alongside exome sequencing.

- name: Crisis laboratory and cardiac evaluation
  description: >-
    During illness or crisis, obtain serial creatine kinase, glucose, blood gas
    and lactate, electrolytes including magnesium, transaminases, renal function
    and urine myoglobin, together with continuous ECG/telemetry with repeated QTc
    assessment and echocardiography. Normal interictal acylcarnitines, lactate,
    carnitine or respiratory-chain studies do not exclude the diagnosis.
  evidence:
  - reference: PMID:34668327
    reference_title: >-
      Variable clinical severity in TANGO2 deficiency: Case series and literature review.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Findings such as elevated creatine kinase, hypothyroidism, ketotic hypoglycemia, QT prolongation, or abnormalities of long-chain acylcarnitines and urine dicarboxylic acids should raise clinical suspicion for this life-threatening condition.
    explanation: Lists the laboratory findings that should trigger evaluation for TDD.
  - reference: PMID:32929747
    reference_title: >-
      Clinical and biological characterization of 20 patients with TANGO2 deficiency indicates novel triggers of metabolic crises and no primary energetic defect.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Unexpectedly, plasma acylcarnitines, plasma FGF-21, muscle histology, and mitochondrial spectrometry were mostly normal.
    explanation: Supports the caution that standard metabolic workup is frequently normal and cannot exclude TDD.
  - reference: PMID:29369572
    reference_title: >-
      TANGO2 Deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: monitor creatine phosphokinase; EKG to monitor QTc and for development of type 1 Brugada pattern; continuous rhythm monitoring for arrhythmias including premature ventricular contractions, ventricular tachycardia, and torsade de pointes
    explanation: >-
      Sources the creatine kinase, serial QTc and continuous rhythm-monitoring
      elements of the crisis evaluation panel. Evidence source is OTHER because
      this is a GeneReviews chapter.

differential_diagnoses:
- name: 22q11.2 deletion syndrome
  description: >-
    A 22q11.2 deletion is both a differential diagnosis and a risk state: TANGO2
    lies inside the deleted interval, so an individual with 22q11.2 deletion
    syndrome who develops rhabdomyolysis, metabolic crises or ventricular
    arrhythmia should be evaluated for a pathogenic variant on the remaining
    TANGO2 allele rather than having those features attributed to the deletion
    syndrome alone.
  disease_term:
    preferred_term: 22q11.2 deletion syndrome
    term:
      id: MONDO:0018923
      label: 22q11.2 deletion syndrome
  evidence:
  - reference: PMID:38829177
    reference_title: >-
      Multicenter appraisal of comorbid TANGO2 deficiency disorder in patients with 22q11.2 deletion syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Although patients with 22q11.2DS are at substantially higher risk for comorbid TDD, it remains underdiagnosed within 22q11.2DS, likely due to overlapping symptomatology and a lack of knowledge about TDD.
    explanation: Supports both the phenotypic overlap and the recommendation to look for comorbid TDD.

- name: Fatty acid oxidation disorders
  description: >-
    Disorders of mitochondrial fatty-acid oxidation share fasting-triggered
    hypoketotic hypoglycaemia, rhabdomyolysis, cardiomyopathy and arrhythmia, and
    TDD can present with acylcarnitine abnormalities suggestive of a
    beta-oxidation defect. They are distinguished by a consistent, diagnostic
    acylcarnitine profile and by the absence of the TDD neurodevelopmental and
    TANGO2-spell phenotype.
  evidence:
  - reference: PMID:34668327
    reference_title: >-
      Variable clinical severity in TANGO2 deficiency: Case series and literature review.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We present biochemical and clinical data to help highlight the features that aid in consideration of this condition in the differential with disorders of fatty acid oxidation.
    explanation: Explicitly frames fatty-acid oxidation disorders as the key differential.

- name: Primary mitochondrial disease
  description: >-
    TDD was initially classified among mitochondrial disorders, and secondary
    respiratory-chain and coenzyme Q10 abnormalities are reported in muscle. It is
    distinguished by the absence of a constitutive primary energetic defect, with
    normal interictal acylcarnitines, FGF-21, muscle histology and mitochondrial
    spectrometry in most patients.
  evidence:
  - reference: PMID:32929747
    reference_title: >-
      Clinical and biological characterization of 20 patients with TANGO2 deficiency indicates novel triggers of metabolic crises and no primary energetic defect.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Mechanistically, TANGO2 disease is unlikely to originate from a primary mitochondrial defect.
    explanation: Supports the distinction from primary mitochondrial cytopathy.
  - reference: PMID:31339582
    reference_title: >-
      Clinical presentation and proteomic signature of patients with TANGO2 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: a defect of multiple respiratory chain enzymes and coenzyme Q10 (CoQ10 ) in two cases, suggesting a possible secondary defect of oxidative phosphorylation
    explanation: >-
      Recorded as PARTIAL because respiratory-chain abnormalities do occur in a
      minority, which is precisely why the differential is difficult; the authors
      interpret them as secondary.

- name: Inherited long QT and Brugada syndromes
  description: >-
    TDD produces marked QTc prolongation and, in about a quarter of crises, a type
    I Brugada pattern, which can prompt a primary channelopathy diagnosis. TDD is
    distinguished by the crisis-conditional, metabolically triggered nature of the
    repolarization abnormality, its association with rhabdomyolysis and
    encephalopathy, and its poor response to standard antiarrhythmic drugs.
  evidence:
  - reference: PMID:35568137
    reference_title: >-
      Cardiac crises: Cardiac arrhythmias and cardiomyopathy during TANGO2 deficiency related metabolic crises.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: During crisis, QTc prolongation occurred in all (median 547 ms; IQR 504-600 ms) and a type I Brugada pattern in 8 (26%).
    explanation: Documents the channelopathy-mimicking electrocardiographic phenotype.
  - reference: PMID:38855866
    reference_title: >-
      Folate as a potential treatment for lethal ventricular arrhythmias in TANGO2-deficiency disorder.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: TDD-associated cardiac arrhythmias are recalcitrant to standard antiarrhythmic medications and constitute the leading cause of death.
    explanation: >-
      Supports the distinguishing feature of refractoriness to conventional
      antiarrhythmic therapy. Evidence source is OTHER because this is the
      framing statement of an iPSC-cardiomyocyte study.

animal_models:
- species: Danio rerio
  genotype: tango2 loss-of-function mutant and morpholino knockdown
  category: Loss-of-function mutant and knockdown, with extrinsic stress challenge
  genes:
  - preferred_term: TANGO2
    term:
      id: hgnc:25439
      label: TANGO2
  description: >-
    Zebrafish tango2 mutants show growth defects, early lethality and heightened
    susceptibility of skeletal muscle to extrinsic triggers, closely mirroring the
    stress-conditional rhabdomyolysis of patients.
    Lipidomics in the same model identified glycerolipid-pathway alterations, and a
    separate knockdown study linked the rhabdomyolysis phenotype to autophagy and
    mitophagy failure with rescue by calpeptin. The model is well suited to trigger
    and rescue studies but does not reproduce the full human neurocardiac
    phenotype.
  associated_phenotypes:
  - Rhabdomyolysis
  - Muscle Weakness
  evidence:
  - reference: PMID:37577943
    reference_title: >-
      Intrinsic and extrinsic regulation of rhabdomyolysis susceptibility by Tango2.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: we demonstrate that the loss of Tango2 in zebrafish results in growth defects, early lethality and increased susceptibility of skeletal muscle defects in response to extrinsic triggers, similar to TANGO2-deficient patients
    explanation: Establishes the model and its recapitulation of trigger-dependent muscle injury.
  - reference: PMID:39722856
    reference_title: >-
      TANGO2-related rhabdomyolysis symptoms are associated with abnormal autophagy functioning.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Calpeptin treatment was sufficient to rescue the locomotor properties thanks to its beneficial effect on autophagy functioning in zebrafish and to improve LC3-II levels in starved primary muscle cells of TANGO2 patients.
    explanation: Demonstrates a pharmacological rescue acting through autophagy in the same model.

- species: Mus musculus
  genotype: Constitutive Tango2 knockout and oligodendrocyte-specific conditional knockout
  category: Knockout and cell-type-specific conditional knockout, with vitamin B5 rescue
  genes:
  - preferred_term: TANGO2
    term:
      id: hgnc:25439
      label: TANGO2
  description: >-
    Constitutive and oligodendrocyte-specific Tango2 knockout mice reproduce the
    motor deficits of TDD, with cerebellar myelin loss and disturbed phospholipid
    metabolism that are alleviated by vitamin B5. An independent knockout line
    shows impaired intermediate-filament structure with fragmented mitochondrial
    networks and, in male mice, heart defects, reduced muscle function and glucose
    intolerance culminating in desminopathy. Earlier reports of grossly normal
    knockout mice mean that phenotype penetrance in mouse is line- and
    condition-dependent.
  associated_phenotypes:
  - Ataxia
  - Cardiomyopathy
  evidence:
  - reference: PMID:42522778
    reference_title: >-
      Oligodendroglial TANGO2 Regulates Lipid Metabolism to Control Motor Coordination.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Behavioral analyses revealed that both constitutive and oligodendrocyte-specific deletion of Tango2 recapitulate the motor deficits associated with individuals with TDD.
    explanation: Establishes motor-phenotype recapitulation and its oligodendroglial origin.
  - reference: PMID:40480980
    reference_title: >-
      TANGO2 binds crystallin alpha B and its loss causes desminopathy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: In male mice, loss of TANGO2 caused heart defects, reduced muscle function and glucose intolerance by remodelling of intermediate filaments, which altered the mitochondrial and cytoplasmic proteomes, N-glycosylation and nucleocytoplasmic O-GlcNAcylation.
    explanation: Documents cardiac, muscular and metabolic phenotypes in an independent knockout line.

- species: Drosophila melanogaster
  genotype: TANGO2 (CG31938) loss-of-function allele
  category: Loss-of-function mutant with starvation and heat-stress challenge and vitamin rescue
  description: >-
    A Drosophila model of TANGO2 loss reproduces starvation sensitivity,
    heat-induced seizure susceptibility and locomotor impairment. It was the system
    in which vitamin B5 rescue was first demonstrated, with a weaker partial rescue
    by vitamin B3, and it provided the rationale for B-complex supplementation in
    patients.
  associated_phenotypes:
  - Seizures
  evidence:
  - reference: PMID:36502486
    reference_title: >-
      Vitamin B5, a coenzyme A precursor, rescues TANGO2 deficiency disease-associated defects in Drosophila and human cells.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Here, we describe a model of TANGO2-related disease in the fruit fly Drosophila melanogaster that recapitulates crucial disease traits.
    explanation: Establishes the fly model and its recapitulation of disease traits.
  - reference: PMID:36502486
    reference_title: >-
      Vitamin B5, a coenzyme A precursor, rescues TANGO2 deficiency disease-associated defects in Drosophila and human cells.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: We also observed a partial rescue of one of the fly defects by vitamin B3, though to a lesser extent than vitamin B5.
    explanation: Documents the vitamin specificity of the rescue in the fly model.

experimental_models:
- name: Patient-derived and CRISPR-engineered iPSC cardiomyocytes
  description: >-
    Induced pluripotent stem cell-derived cardiomyocytes from individuals with TDD
    recapitulate the key electrophysiological abnormalities, and these are rescued
    by adenoviral wild-type TANGO2 expression or CRISPR correction of the
    pathogenic variant, establishing causality. An independent CRISPR line carrying
    the exon 3-9 deletion showed that the electrophysiological defect is
    substrate-conditional and mediated by ATP depletion and TRPM4 upregulation.
    This is currently the most disease-proximal platform for the arrhythmia arm.
  evidence:
  - reference: PMID:38855866
    reference_title: >-
      Folate as a potential treatment for lethal ventricular arrhythmias in TANGO2-deficiency disorder.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Here, we established potentially novel patient-derived induced pluripotent stem cell differentiated cardiomyocyte (iPSC-CM) models that recapitulate key electrophysiological abnormalities in TDD. These electrophysiological abnormalities were rescued in iPSC-CMs with either adenoviral expression of WT-TANGO2 or correction of the pathogenic variant using CRISPR editing.
    explanation: Establishes the platform and its genetic-rescue validation.
  - reference: PMID:42389941
    reference_title: >-
      Metabolic crisis and TRPM4 activation cause QT prolongation in TANGO2 deficiency disorder.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: CRISPR/Cas9 were used to generate human induced pluripotent stem cell cardiomyocytes (hiPSC-CMs) carrying a TANGO2 exon 3-9 deletion (TANGO2-/-).
    explanation: Documents the independent isogenic CRISPR cardiomyocyte model.

- name: Patient fibroblasts and primary myoblasts
  description: >-
    Skin fibroblasts and primary myoblasts from affected individuals are the
    workhorse system for trafficking, lipidomic, respiration, reactive oxygen
    species and nutrient-stress assays, and they show reduced TANGO2 protein on
    immunoblot. They cannot model excitable tissue physiology.
  evidence:
  - reference: PMID:31339582
    reference_title: >-
      Clinical presentation and proteomic signature of patients with TANGO2 mutations.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Immunoblot analysis detected a significant decrease of TANGO2 protein.
    explanation: Demonstrates that patient-derived cells report the molecular loss of function directly.
  - reference: PMID:39722856
    reference_title: >-
      TANGO2-related rhabdomyolysis symptoms are associated with abnormal autophagy functioning.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Autophagy functioning was analyzed in vitro, in primary skeletal myoblasts from TANGO2 patients, in basal and fasting conditions
    explanation: Illustrates the use of patient primary myoblasts under nutrient stress.

clinical_trials:
- name: NCT05374616
  status: RECRUITING
  description: >-
    Baylor College of Medicine observational natural-history study and
    biorepository for TANGO2-related disorder, collecting longitudinal clinical
    data plus blood, saliva and fibroblast specimens. It is non-interventional
    and is not a treatment-efficacy study, so it cannot resolve the open question
    of whether B-vitamin supplementation prevents crises; it is nonetheless the
    principal registered study in this disorder and the source of the
    natural-history cohorts cited throughout this entry.
  target_phenotypes:
  - preferred_term: Encephalopathy
    term:
      id: HP:0001298
      label: Encephalopathy
  - preferred_term: Ventricular tachycardia
    term:
      id: HP:0004756
      label: Ventricular tachycardia
  evidence:
  - reference: clinicaltrials:NCT05374616
    reference_title: >-
      Natural History Study and Establishment of a Biorepository-TANGO2-related Disorder
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The study aims to establish a biorepository of individuals with TANGO2 deficiency to support scientific research and establish a comprehensive clinical database of affected individuals to understand the disease course.
    explanation: The registry's own description of its biorepository and natural-history objectives.

notes: >-
  Evidence-strength calibration. Three claims in this entry are deliberately
  curated below the confidence with which they are often stated in reviews.
  (1) B-vitamin supplementation is recommended in GeneReviews and supported by two
  independent retrospective natural-history analyses plus convergent rescue in
  flies, mice, human cells and iPSC cardiomyocytes, but it has never been tested in
  a randomized controlled trial; dose, formulation, long-term safety in children
  and the identity of the active vitamin(s) all remain open.
  (2) The primary molecular function of TANGO2 is unsettled: the acyl-CoA-binding
  model and the CRYAB/desmin intermediate-filament model are both supported by
  strong primary data and have not been reconciled, and a proposed heme-transport
  role for TANGO2 homologues remains unresolved.
  (3) The mitochondrial phenotype is stress-conditional and secondary; TDD should
  not be curated as a primary respiratory-chain disorder.

  Module conformance. Conformance to metabolic_intoxication_decompensation is
  declared on the energy-deficit, decompensation and encephalopathy nodes only. The
  module's trigger node ("Enzymatic Block in Intermediary Metabolism") is
  deliberately not claimed because TANGO2 is a lipid-binding/trafficking protein
  rather than a metabolic enzyme, and the accumulating species are
  lysophospholipids and free fatty acids rather than a classical organic acid or
  ammonia. Conformance to cardiac_ion_channel_repolarization is declared on the
  altered-action-potential, arrhythmogenic-substrate and
  ventricular-tachyarrhythmia nodes; the module's trigger node ("Cardiac
  Ion-Channel or Calcium-Handling Variant") is deliberately not claimed because TDD
  reaches the arrhythmogenic substrate through metabolic ATP depletion and
  secondary TRPM4 upregulation rather than through an inherited ion-channel
  variant, and TDD hearts are frequently not structurally normal during a crisis.

  Relationship to 22q11.2 deletion syndrome. This entry curates the TDD side of the
  relationship. The 22q11.2 Deletion Syndrome entry independently carries the same
  relationship as a diagnostic red flag and a differential diagnosis; the two
  entries are intended to be complementary and non-contradictory. Neither asserts
  that TANGO2 hemizygosity alone causes TDD - a pathogenic variant on the remaining
  allele is required.

  Deep research provenance. A Falcon (Edison Scientific) deep-research report for
  this disease is archived under research/. It supplied leads only: it reported
  DOIs rather than PMIDs, so every reference used here was independently resolved,
  fetched into references_cache/ with just fetch-reference, and had its snippet
  verified as an exact substring of the cached abstract. Several of the strongest
  sources used here (the 73-patient natural history, the TRPM4/QT mechanism, the
  acyl-CoA-binding and CRYAB structural work, the oligodendroglial mouse) post-date
  or were absent from that report. The report's single artifact is a markdown
  summary table, not an image, so no evidence item carries an images: attachment.

📚

References & Deep Research

References

1

PMID:29369572

TANGO2 Deficiency.

No top-level findings curated for this source.

Deep Research

1

Falcon ▸

TANGO2 Deficiency Disorder: Disease-Characteristics Research Report

Edison Scientific Literature 44 citations 2026-07-31T01:39:59.888823

TANGO2 Deficiency Disorder: Disease-Characteristics Research Report

Scope and evidence note. This synthesis emphasizes primary human and experimental studies through 2024. The retrieved bibliographic records did not expose PMID fields reliably; therefore, DOI and ClinicalTrials.gov URLs are supplied rather than inferred. Frequency estimates come from selected rare-disease cohorts and should not be interpreted as population prevalence. Short quotations are reproduced only where supported by retrieved abstracts.

Executive summary

TANGO2 deficiency disorder (TDD) is a rare, autosomal-recessive, multisystem Mendelian disease caused by biallelic pathogenic loss-of-function variants in TANGO2 at 22q11.21. Its defining combination is neurodevelopmental impairment plus stress-triggered metabolic crises, rhabdomyolysis, QT prolongation, malignant ventricular arrhythmias, and sometimes transient cardiomyopathy. Neurologic deterioration, seizures, ataxia, movement abnormalities, hypothyroidism, feeding problems, and episodic “TANGO2 spells” broaden the phenotype. Illness, fever, fasting, dehydration, reduced food intake, physical exertion, heat, and possibly selected anesthetics can precipitate episodes. The leading immediate threat is arrhythmic cardiac arrest during a metabolic crisis. (heiman2022mitochondrialdysfunctionassociated pages 1-2, miyake2022cardiaccrisescardiac pages 1-2, berat2021clinicalandbiological pages 1-7)

The best-supported mechanistic model is no longer simply a generic primary respiratory-chain disorder. Evidence instead converges on stress-sensitive disruption of lipid/acyl-CoA homeostasis, phosphatidic-acid and glycerolipid metabolism, membrane trafficking, and context-dependent mitochondrial function, causing ROS/lipid peroxidation and energetic/membrane failure in skeletal muscle, cardiomyocytes, and neural tissues. Important uncertainties remain about TANGO2’s exact biochemical activity, subcellular localization, and proposed role in heme transport. (heiman2022mitochondrialdysfunctionassociated pages 1-2, kim2023intrinsicandextrinsic pages 1-3, lujan2023defectsinlipid pages 1-2)

A major 2023–2024 development is convergent evidence for B vitamins: pantothenate/B5 rescues Drosophila and human-cell defects; folate/B9 nearly abolishes arrhythmias in patient-derived cardiomyocytes; and retrospective natural-history observations associate multivitamin/B-complex use with fewer crises. These findings are biologically compelling but not yet validated in randomized clinical trials. (asadi2023vitaminb5a pages 6-8, xu2024folateasa pages 1-2, asadi2023vitaminb5a pages 8-9)

The following table summarizes the principal evidence base.

domain	strongest finding/statistic	evidence type/sample	source year and DOI/URL	confidence/limitation
Identifiers / genetics	TANGO2 deficiency disorder is an autosomal recessive disease caused by biallelic TANGO2 variants; disease mapping available as MONDO_0018820, and phenotype MIM/OMIM 616878 is cited in the literature; common recurrent alleles include the exon 3-9 deletion and c.460G>A (p.Gly154Arg) in some Hispanic/Latino families	Disease database + human clinical genetics; multiple cohorts	2024 Open Targets disease-target association; 2022 Scientific Reports doi:10.1038/s41598-022-07076-9; 2019 JIMD doi:10.1002/jimd.12156; https://platform.opentargets.org (OpenTargets Search: TANGO2 deficiency disorder-TANGO2, heiman2022mitochondrialdysfunctionassociated pages 1-2, mingirulli2020clinicalpresentationand pages 2-3)	High confidence for gene-disease validity and AR inheritance; variant-frequency details remain cohort-dependent and not population-screened globally
20-patient phenotype cohort	In 20 patients from 14 families, neurodevelopmental delay occurred in 85% (17/20), acute metabolic crises in 85% (17/20), hypothyroidism in 60% (12/20); among crises: rhabdomyolysis 88% (15/17), neurologic symptoms 82% (14/17), cardiac features 71% (12/17)	Human multicenter cohort, n=20	2020/2021 J Inherit Metab Dis doi:10.1002/jimd.12314 https://doi.org/10.1002/jimd.12314 (berat2021clinicalandbiological pages 1-7, berat2021clinicalandbiological pages 12-17)	High confidence for broad phenotype spectrum; modest sample size and referral-center ascertainment bias
27-patient cardiac crisis series	In 27 patients across 43 crisis admissions, QTc prolongation occurred in 100% with median QTc 547 ms; ventricular tachycardia in 78%, cardiomyopathy in 70%, cardiac arrest in 74%, mortality 37% (10 deaths; 6 arrhythmia-related)	Human retrospective multicenter cardiac crisis study, n=27 patients / 43 admissions	2022 Heart Rhythm doi:10.1016/j.hrthm.2022.05.009 https://doi.org/10.1016/j.hrthm.2022.05.009 (miyake2022cardiaccrisescardiac pages 1-2)	High confidence for severity during crises; estimates apply to severe admissions rather than all diagnosed patients
2024 22q11.2 screening implementation	In 435 patients with 22q11.2 deletion syndrome, 21 met symptom-based criteria for TANGO2 testing, 9 underwent sequencing, and 0 were diagnosed with TDD; authors highlight underdiagnosis risk because TANGO2 lies within the deleted interval	Human retrospective multicenter screening study, n=435	2024 Am J Med Genet A doi:10.1002/ajmg.a.63778 https://doi.org/10.1002/ajmg.a.63778 (owlett2024multicenterappraisalof pages 1-3)	Moderate confidence; useful implementation evidence, but negative yield may reflect incomplete testing and retrospective design
Lipid / acyl-CoA mechanism	TANGO2-deficient cells showed increased lysophosphatidic acid and decreased phosphatidic acid, enlarged lipid droplets, elevated ROS, and nutrient-sensitive worsening; authors propose impaired acyl-CoA availability for LPA-to-PA acylation	Experimental cell biology and lipidomics in HepG2 cells and patient fibroblasts	2023 eLife doi:10.7554/eLife.85345 https://doi.org/10.7554/eLife.85345 (lujan2023defectsinlipid pages 1-2)	Moderate-high confidence for lipid-homeostasis mechanism; exact primary molecular function of TANGO2 remains unsettled
Zebrafish model	tango2 loss caused growth defects, early lethality, smaller myofibers, and increased skeletal-muscle susceptibility to extrinsic stressors; 96% mortality by 3 months was reported in the model summary	Model organism study, zebrafish mutants	2023 Dis Model Mech doi:10.1242/dmm.050092 https://doi.org/10.1242/dmm.050092 (kim2023intrinsicandextrinsic pages 1-3, kim2023intrinsicandextrinsic pages 3-5)	Moderate confidence; strong for stress-sensitive muscle phenotype, but fish may not capture full human neurocardiac disease
Vitamin B5 rescue	Pantothenic acid (vitamin B5) rescued multiple TANGO2-associated defects in Drosophila and restored trafficking defects in human cells; in flies, starvation survival improved to ~25 h at 50% survival versus ~12 h untreated, and heat-induced seizures were reduced by ~95%	Drosophila + human cell rescue experiments	2023 J Inherit Metab Dis doi:10.1002/jimd.12579 https://doi.org/10.1002/jimd.12579 (asadi2023vitaminb5a pages 6-8, asadi2023vitaminb5a pages 1-3)	Moderate confidence preclinically; no randomized human efficacy trial yet
Vitamin B9 iPSC-cardiomyocyte rescue	High-dose folate virtually abolished arrhythmias in patient-derived iPSC-cardiomyocytes; rescue was blocked by methotrexate, supporting an intracellular folate-dependent mechanism	Human iPSC-cardiomyocyte disease model + supportive natural-history observation	2024 JCI Insight doi:10.1172/jci.insight.171005 https://doi.org/10.1172/jci.insight.171005 (xu2024folateasa pages 1-2)	Moderate confidence for mechanistic antiarrhythmic potential; clinical benefit in patients remains observational, not trial-proven
Current study infrastructure	NCT05374616 is a recruiting observational natural-history/biorepository study with planned enrollment of 300 and estimated completion in 2030; primary outcome tracks metabolic and cardiac crises over 10 years	ClinicalTrials.gov observational registry/biorepository	ClinicalTrials.gov NCT05374616 https://clinicaltrials.gov/study/NCT05374616 (NCT05374616 chunk 1)	High confidence for real-world implementation status; non-interventional and not a treatment-efficacy study

Table: This table summarizes the strongest available evidence across clinical, mechanistic, therapeutic, and implementation domains for TANGO2 deficiency disorder. It highlights where the evidence is strongest and where major limitations remain.

1. Disease information

Definition and identifiers

TDD is an autosomal-recessive metabolic encephalomyopathic and arrhythmia syndrome caused by biallelic pathogenic variants in TANGO2. Open Targets maps it to MONDO:0018820, “recurrent metabolic encephalomyopathic crises–rhabdomyolysis–cardiac arrhythmia–intellectual disability syndrome,” associated with TANGO2/ENSG00000183597. The phenotype is cited as OMIM/MIM 616878. (OpenTargets Search: TANGO2 deficiency disorder-TANGO2, heiman2022mitochondrialdysfunctionassociated pages 1-2)

Common names include:

TANGO2 deficiency disorder/disease;
TANGO2-related disorder;
TANGO2-related metabolic encephalomyopathic crises;
metabolic encephalomyopathic crises, recurrent, with rhabdomyolysis, cardiac arrhythmias, and neurodegeneration;
TANGO2-related metabolic encephalopathy and arrhythmias, sometimes abbreviated TRMEA;
recurrent metabolic encephalomyopathic crises–rhabdomyolysis–cardiac arrhythmia–intellectual disability syndrome.

No disease-specific ICD-10, ICD-11, or MeSH identifier was established in the retrieved evidence; clinical coding generally requires phenotype-level codes for genetic/metabolic disease, rhabdomyolysis, arrhythmia, epilepsy, developmental disorder, or hypothyroidism. A dedicated SNOMED CT concept was likewise not verified.

Evidence granularity. The literature combines individual medical records and biospecimens with aggregated disease-level resources. Human cohorts are retrospective or observational and include 9-, 14-, 20-, 27-, and 73-patient series; experimental evidence comes from patient fibroblasts/myoblasts, HepG2 cells, patient-derived iPSC cardiomyocytes, Drosophila, zebrafish, and mice. (miyake2022cardiaccrisescardiac pages 1-2, berat2021clinicalandbiological pages 12-17, dines2019tango2expandingthe pages 5-6, mingirulli2020clinicalpresentationand pages 1-2, sandkuhler2026crossspeciesevaluationof pages 15-16)

2. Etiology, risk, protection, and gene–environment interaction

Causal factors

The necessary cause is biallelic germline pathogenic variation in TANGO2, usually resulting in absent or severely reduced protein/function. Environmental agents do not independently cause the Mendelian disorder. Rather, they reveal the latent metabolic vulnerability and determine crisis timing and severity. (heiman2022mitochondrialdysfunctionassociated pages 1-2, owlett2024multicenterappraisalof pages 1-3)

Genetic risk factors

Reported pathogenic classes include multiexon deletions, nonsense, frameshift, canonical splice, small in-frame deletion, and missense variants. Important examples are the recurrent exon 3–9 deletion, c.460G>A (p.Gly154Arg), c.262C>T (p.Arg88*), c.220A>C (p.Thr74Pro), c.380+1G>A, and c.711-3C>G, the last experimentally associated with aberrant splicing. In one early dataset, the exon 3–9 deletion was prominent among European-ancestry cases, whereas p.Gly154Arg was recurrent in Hispanic/Latino cases; these are ancestry-associated observations, not universal founder-frequency estimates. (berat2021clinicalandbiological pages 12-17, mingirulli2020clinicalpresentationand pages 2-3, dines2019tango2expandingthe pages 5-6, mingirulli2020clinicalpresentationand pages 1-2)

TANGO2 lies in the recurrently deleted 22q11.2/DiGeorge region. A person with a 22q11.2 deletion that removes one TANGO2 allele is at risk of TDD if the remaining allele carries a pathogenic variant. A 2024 multicenter study screened 435 people with 22q11.2 deletion syndrome: 21 met symptom-based testing criteria, 9 underwent sequencing/deletion-duplication analysis, and none was confirmed, illustrating both low absolute yield and the danger of symptom overlap. (owlett2024multicenterappraisalof pages 1-3)

Environmental and lifestyle risk factors

Established crisis triggers are intercurrent illness—especially febrile or viral illness—fasting, dehydration, reduced intake, heat, and physical exertion. Selected anesthetic exposures and possibly carnitine supplementation were proposed as additional triggers in a 20-patient cohort; these observations require cautious interpretation and specialist review rather than blanket contraindication. (kim2023intrinsicandextrinsic pages 1-3, NCT05374616 chunk 1, berat2021clinicalandbiological pages 1-7)

Smoking, alcohol, pollution, occupational exposure, radiation, and chronic dietary patterns have no demonstrated etiologic role. Infectious organisms are triggers, not causal pathogens, and TDD is not communicable.

Protective factors

Avoiding prolonged fasting and dehydration, prompt treatment of illness, early carbohydrate-containing fluids plus complete nutrition, and avoidance of unnecessary heat/exertional stress during illness are clinically plausible protective measures. Glucose-containing fluids alone did not reliably prevent cardiac crisis; adequate feeding and micronutrient provision appear important. (miyake2022cardiaccrisescardiac pages 8-9)

B-complex or multivitamin supplementation is the leading candidate environmental protective factor. Human support remains observational, while B5 and B9 have direct rescue evidence in model systems. No protective TANGO2 allele or validated modifier gene has been identified. Intrafamilial variability strongly suggests modifiers, but none is established. (heiman2022mitochondrialdysfunctionassociated pages 1-2, xu2024folateasa pages 1-2, asadi2023vitaminb5a pages 8-9)

Gene–environment causal interaction

A useful causal model is:

biallelic TANGO2 loss → impaired lipid/acyl-CoA and membrane homeostasis ± mitochondrial/ER–Golgi dysfunction → reduced reserve in muscle, heart, and nervous system → fasting/illness/heat/exertion increases substrate demand and oxidative stress → rhabdomyolysis and metabolic decompensation → QT prolongation/cardiomyopathy → polymorphic VT, cardiac arrest, or death. (kim2023intrinsicandextrinsic pages 1-3, lujan2023defectsinlipid pages 1-2)

3. Phenotypes

Core phenotype frequencies and characteristics

In a 20-patient cohort, neurodevelopmental delay occurred in 17/20 (85%), acute metabolic crises in 17/20 (85%), and hypothyroidism in 12/20 (60%). Among the 17 with crises, rhabdomyolysis occurred in 15/17 (88%), neurologic manifestations in 14/17 (82%), and cardiac findings in 12/17 (71%). Long QT occurred in 10/17, Brugada-like pattern in 2/17, and arrhythmia in 6/17. (berat2021clinicalandbiological pages 1-7)

Suggested phenotype annotations follow; frequencies are cohort-specific.

Global developmental delay/intellectual disability—usually infancy or childhood onset, variable severity, often progressive or worsened after crises; poor speech is common. Suggested HPO: Global developmental delay (HP:0001263), Intellectual disability (HP:0001249), Delayed speech and language development (HP:0000750). Progressive delay preceded crises in 14/20 in one series. (berat2021clinicalandbiological pages 12-17, mingirulli2020clinicalpresentationand pages 2-3)
Developmental regression/neurodegeneration—episodic or progressive, sometimes crisis-associated; major effects on communication, schooling, independence, and caregiving burden. HPO: Developmental regression (HP:0002376), Neurodevelopmental regression.
Seizures/epilepsy—childhood onset, variable and occasionally treatment-resistant; generalized and myoclonic forms are reported. HPO: Seizure (HP:0001250), Generalized myoclonic seizure (HP:0002123). (dołega2024clinicalspectrumdiagnosis pages 4-7)
Ataxia, gait abnormality, dysarthria, spasticity, dystonia, hypotonia—chronic progressive or episodic, causing falls and loss of mobility. HPO: Ataxia (HP:0001251), Gait disturbance (HP:0001288), Dysarthria (HP:0001260), Spasticity (HP:0001257), Dystonia (HP:0001332), Muscular hypotonia (HP:0001252). (dołega2024clinicalspectrumdiagnosis pages 4-7, mingirulli2020clinicalpresentationand pages 2-3)
TANGO2 spells—transient ataxia, weakness, and dyskinesia, often after waking; physical activity, heat, or reduced intake may trigger episodes lasting minutes to hours. Suggested HPO: Episodic ataxia (HP:0002131), Episodic weakness, Dyskinesia. (dołega2024clinicalspectrumdiagnosis pages 4-7)
Rhabdomyolysis/myalgia/weakness—episodic and potentially severe, generally precipitated by metabolic stress. HPO: Rhabdomyolysis (HP:0003201), Myalgia (HP:0003326), Muscle weakness (HP:0001324), Myoglobinuria (HP:0002913). Crisis CK has ranged from 419 to 400,000 U/L in reported cohorts; one French case reached 43,670 IU/L. (kim2023intrinsicandextrinsic pages 1-3, berat2021clinicalandbiological pages 12-17, mingirulli2020clinicalpresentationand pages 2-3)
Metabolic crisis/encephalopathy—acute and episodic, with hypoglycemia, lactic/metabolic acidosis, hyperammonemia, elevated transaminases, and sometimes coma. HPO: Hypoglycemia (HP:0001943), Lactic acidosis (HP:0003128), Hyperammonemia (HP:0001987), Encephalopathy (HP:0001298), Elevated serum creatine kinase (HP:0003236). Baseline metabolic studies may be normal between episodes. (heiman2022mitochondrialdysfunctionassociated pages 1-2, berat2021clinicalandbiological pages 12-17)
QT prolongation and ventricular arrhythmia—episodic, crisis-linked, rapidly life-threatening. HPO: Prolonged QT interval (HP:0001657), Ventricular tachycardia (HP:0004756), Torsade de pointes (HP:0001664), Cardiac arrest (HP:0001695). In 43 severe admissions involving 27 patients, QTc prolongation was universal, median QTc 547 ms, VT occurred in 78%, and cardiac arrest in 74%. (miyake2022cardiaccrisescardiac pages 1-2)
Cardiomyopathy/ventricular dysfunction—usually crisis-associated and potentially reversible, but severe cases require ECMO or rarely transplantation. HPO: Cardiomyopathy (HP:0001638), Decreased left ventricular ejection fraction (HP:0012664). It occurred in 70% of severe cardiac-crisis admissions. (miyake2022cardiaccrisescardiac pages 1-2)
Hypothyroidism/TSH elevation—chronic, variable, treatable. HPO: Hypothyroidism (HP:0000821), Elevated thyroid-stimulating hormone (HP:0002925). TSH elevation occurred in 8/9 patients in one series and hypothyroidism in 12/20 in another. (mingirulli2020clinicalpresentationand pages 2-3, berat2021clinicalandbiological pages 1-7)
Feeding difficulty—chronic and functionally important; 8/14 had gastrointestinal/feeding involvement in one cohort, sometimes requiring gastrostomy. HPO: Feeding difficulties (HP:0011968), Gastrostomy tube feeding. (dines2019tango2expandingthe pages 5-6)
Neuroimaging abnormalities—variable ventriculomegaly, cerebral/white-matter atrophy, white-matter change, or microcephaly. MRI was abnormal in 9/16 in one cohort. HPO: Cerebral atrophy (HP:0002059), Ventriculomegaly (HP:0002119), Abnormal cerebral white matter morphology (HP:0002500), Progressive microcephaly (HP:0000253). (berat2021clinicalandbiological pages 12-17)
Hearing impairment is reported but insufficiently quantified. HPO: Hearing impairment (HP:0000365). (dołega2024clinicalspectrumdiagnosis pages 4-7)

No validated TDD-specific EQ-5D, SF-36, PROMIS, or quality-of-life dataset was identified. Nevertheless, recurrent ICU admission, neurodevelopmental disability, epilepsy, feeding support, mobility loss, and sudden-death risk imply major patient and caregiver burden.

4. Genetic and molecular information

Causal gene: TANGO2, approved name transport and Golgi organization 2 homolog; Ensembl ENSG00000183597; chromosome 22q11.21. The retrieved sources did not provide a verified HGNC numerical identifier, so none is inferred. (OpenTargets Search: TANGO2 deficiency disorder-TANGO2, heiman2022mitochondrialdysfunctionassociated pages 1-2)

Pathogenic variants are constitutional/germline and usually act through loss of function. Somatic causation, gain of function, dominant-negative effects, repeat expansions, mitochondrial-DNA variants, and epigenetic silencing are not established. Pathogenic/likely pathogenic classification should be assigned per ACMG/AMP using population rarity, segregation, predicted loss of function, RNA/protein findings, and phenotype concordance; individual ClinVar classifications must be checked against the current record at testing time.

Large deletions can involve exons 3–9 or arise as part of a broader 22q11.2 deletion. This makes copy-number analysis essential. The allele frequency estimates cited in an early clinical report—approximately 0.0013 for the 34-kb exon 3–9 deletion and 0.0026 for p.Gly154Arg—were ancestry-specific database observations and should not be treated as global carrier frequencies. (mingirulli2020clinicalpresentationand pages 2-3)

No validated modifier gene, protective allele, anticipation, or recurrent germline mosaicism mechanism is known. No disease-specific methylation signature or other epigenetic biomarker was identified. Variable expressivity within families is well documented. (heiman2022mitochondrialdysfunctionassociated pages 1-2, dines2019tango2expandingthe pages 5-6)

5. Environmental information

No toxin, radiation, pollution, occupational exposure, smoking, alcohol, or pathogen causes TDD. Fever/infection, fasting, dehydration, heat, exertion, and reduced intake are clinically important precipitants. Infectious-agent identity is generally less important than the associated catabolic state. Certain anesthetics were proposed as triggers; perioperative planning should therefore involve metabolic, anesthesia, and cardiology specialists. (kim2023intrinsicandextrinsic pages 1-3, berat2021clinicalandbiological pages 1-7)

Ordinary exercise has no demonstrated long-term preventive benefit and vigorous exertion during illness or fasting may be hazardous. Nutritional regularity and avoidance of catabolism are more relevant than a disease-specific macronutrient diet. No evidence supports tobacco/alcohol counseling as disease-specific therapy beyond general health recommendations.

6. Mechanism and pathophysiology

Current mechanistic model

Upstream: TANGO2 loss disturbs acyl-CoA/lipid handling and endomembrane organization. In TANGO2-deficient HepG2 cells and patient fibroblasts, lipidomics showed increased lysophosphatidic acid, decreased phosphatidic acid, reduced cardiolipin, and enlarged lipid droplets. The proposed biochemical lesion is insufficient acyl-CoA availability for LPA acylation to PA. (lujan2023defectsinlipid pages 1-2)

Intermediate: altered phospholipid and neutral-lipid composition impairs membrane integrity, lipid-droplet catabolism, mitochondrial membranes, ER/SR–Golgi trafficking, and fatty-acid utilization. Patient cells show delayed ER-to-Golgi transport, altered ER morphology, decreased stress oxygen consumption/ATP, impaired oleate or palmitate oxidation in some systems, and increased superoxide/ROS. Proteomics implicates fatty-acid oxidation, amino-acid metabolism, plasma membrane, ER–Golgi, and secretory pathways. (heiman2022mitochondrialdysfunctionassociated pages 1-2, kim2023intrinsicandextrinsic pages 1-3)

Downstream: nutrient deprivation or illness intensifies substrate shortage and oxidative stress, causing lipid peroxidation and energetic/membrane failure. Skeletal myofibers undergo necrosis/rhabdomyolysis; cardiomyocytes develop repolarization instability, QT prolongation, ventricular dysfunction, and VT; neural cells likely undergo episodic dysfunction and cumulative injury, producing encephalopathy, seizures, ataxia, and regression. (kim2023intrinsicandextrinsic pages 3-5, lujan2023defectsinlipid pages 1-2)

This framework reconciles conflicting energetic studies: one 20-patient investigation found no evidence of a constitutive primary energetic defect and largely normal baseline acylcarnitines/FGF21, whereas fibroblast and muscle models detect abnormalities under metabolic stress. Thus TDD is best viewed as a stress-sensitive lipid/membrane homeostasis disorder with secondary, context-dependent mitochondrial dysfunction, not a proven primary respiratory-chain enzyme deficiency. (berat2021clinicalandbiological pages 12-17, berat2021clinicalandbiological pages 1-7, heiman2022mitochondrialdysfunctionassociated pages 1-2)

Localization and protein function

TANGO2 has been detected predominantly at mitochondria and at mitochondria–ER–lipid-droplet contact regions in some mammalian systems; other work supports endomembrane, cytosolic, SR, Golgi, or mixed localization. Antibody and fusion-protein limitations contribute to disagreement. A direct acyl-CoA-binding function is plausible but was not definitively established by the 2023 studies retrieved here. Heme trafficking by homologues is an active comparative hypothesis, not yet a settled explanation for human TDD. (heiman2022mitochondrialdysfunctionassociated pages 1-2, kim2023intrinsicandextrinsic pages 3-5, lujan2023defectsinlipid pages 1-2, sandkuhler2026crossspeciesevaluationof pages 15-16)

Suggested ontology annotations

GO biological process: intracellular lipid transport; phospholipid biosynthetic process; glycerolipid metabolic process; fatty-acid beta-oxidation; ER-to-Golgi vesicle-mediated transport; mitochondrial ATP synthesis; response to oxidative stress; regulation of membrane organization; skeletal-muscle tissue development.
GO cellular component: mitochondrion; mitochondrial membrane; endoplasmic reticulum; Golgi apparatus; lipid droplet; sarcoplasmic reticulum; mitochondrion-associated ER membrane.
Cell Ontology: skeletal muscle fiber/myocyte (CL:0000187); cardiomyocyte (CL:0000746); fibroblast (CL:0000057); neuron (CL:0000540); hepatocyte (CL:0000182).

Molecular profiling and advanced technologies

Proteomics: broad changes in mitochondrial fatty-acid oxidation, ER–Golgi, plasma-membrane, amino-acid-metabolism, and secretory proteins. (mingirulli2020clinicalpresentationand pages 1-2, heiman2022mitochondrialdysfunctionassociated pages 1-2)
Lipidomics: increased LPA, decreased PA/cardiolipin, enlarged lipid droplets, glycerolipid abnormalities, and enhanced stress sensitivity. (kim2023intrinsicandextrinsic pages 1-3, lujan2023defectsinlipid pages 1-2)
Metabolomics: no validated diagnostic plasma signature; acylcarnitines and lactate may be normal between crises. (berat2021clinicalandbiological pages 12-17)
iPSC electrophysiology/CRISPR: patient-derived cardiomyocytes recapitulated arrhythmia; wild-type TANGO2 expression or CRISPR correction rescued electrophysiology, supporting causality. (xu2024folateasa pages 1-2)
No replicated single-cell, spatial-transcriptomic, or integrated human multi-omics atlas was identified through 2024.

Relevant abstract quotation from Lujan et al. (published March 2023): “Quantitative lipidomics revealed a marked increase in lysophosphatidic acid (LPA) and a concomitant decrease in its biosynthetic precursor phosphatidic acid (PA).” (lujan2023defectsinlipid pages 1-2)

7. Anatomical structures affected

Primary systems are:

Nervous system: brain/cerebral white matter, cerebellar and motor networks; developmental, epileptic, ataxic, and movement phenotypes. Suggested UBERON: brain (UBERON:0000955), cerebral white matter (UBERON:0002437), cerebellum (UBERON:0002037).
Skeletal muscle: recurrent myofiber injury and rhabdomyolysis. UBERON: skeletal muscle tissue (UBERON:0001134); CL: skeletal muscle fiber (CL:0000187).
Heart: ventricular myocardium and cardiac conduction/repolarization system. UBERON: heart (UBERON:0000948), myocardium (UBERON:0002349); CL: cardiomyocyte (CL:0000746).
Thyroid: frequent hypothyroidism/TSH elevation. UBERON: thyroid gland (UBERON:0002046).
Kidney: secondary risk from myoglobinuria and severe rhabdomyolysis rather than proven primary renal disease. UBERON: kidney (UBERON:0002113).
Liver/metabolic compartment: transaminase elevation and biochemical decompensation occur during crises; direct chronic hepatopathy is not established.

Subcellular structures include mitochondria, ER/SR, Golgi, lipid droplets, and organelle contact sites. No characteristic lateralization is reported; disease is systemic/bilateral.

8. Temporal development

Onset is usually infancy or childhood, reported from 4 months to 8 years. Neurodevelopmental or muscle abnormalities often precede the first metabolic/cardiac crisis. (dołega2024clinicalspectrumdiagnosis pages 1-4, mingirulli2020clinicalpresentationand pages 2-3)

The course is lifelong and combines:

a chronic neurodevelopmental phenotype;
intermittent spells and metabolic crises;
cumulative or stepwise neurologic regression in some patients;
potentially reversible crisis-associated cardiac dysfunction;
persistent risk of sudden death.

There is no formal stage system. A practical clinical staging model is baseline/stable, prodromal catabolic illness, metabolic/rhabdomyolysis crisis, and cardiac crisis/recovery. Critical intervention windows are the earliest phase of illness or fasting, the onset of CK/QTc elevation, and the period before ventricular ectopy progresses to VT. Spontaneous genetic remission does not occur; crisis manifestations can resolve, but developmental disability generally persists.

9. Inheritance and population

Inheritance is autosomal recessive. Parents are usually heterozygous carriers; each pregnancy has a 25% affected, 50% carrier, and 25% unaffected/non-carrier probability when both parental variants are known. Penetrance for biallelic severe loss-of-function appears high, but age-dependent penetrance for individual manifestations and marked variable expressivity complicate counseling.

Consanguinity can increase risk for homozygous alleles but is not required. Founder/population enrichment has been reported for the exon 3–9 deletion in European-ancestry cases, p.Gly154Arg in Hispanic/Latino cases, and exon 4–6 deletion in some Arab families. These patterns require confirmation in population-scale datasets. (heiman2022mitochondrialdysfunctionassociated pages 1-2, mingirulli2020clinicalpresentationand pages 2-3)

A 2024 paper cited a carrier rate near 1 in 350; the same review literature estimated prevalence near 1 per million and approximately 8,000 affected persons worldwide. These figures are uncertain extrapolations, not registry-derived incidence estimates. No reliable annual incidence, sex ratio, or geographic prevalence map exists. Both sexes are affected; no sex-linked mechanism is expected. (owlett2024multicenterappraisalof pages 1-3, dołega2024clinicalspectrumdiagnosis pages 1-4)

There is no repeat-mediated anticipation. Germline mosaicism is theoretically possible for any de novo event but is not a recognized major feature. Cascade testing is appropriate for siblings and extended relatives when familial variants are known.

10. Diagnostics

When to suspect TDD

Suspect TDD in a child with developmental delay, regression, episodic ataxia or weakness, seizures, unexplained CK elevation/rhabdomyolysis, hypoglycemia/lactic acidosis during illness, hypothyroidism, QT prolongation, Brugada-like pattern, or ventricular arrhythmia—especially when several coexist. Consider it specifically in symptomatic individuals with 22q11.2 deletion syndrome. (owlett2024multicenterappraisalof pages 1-3, miyake2022cardiaccrisescardiac pages 1-2)

Acute clinical testing

During illness/crisis, obtain serial:

CK, electrolytes including magnesium and calcium, glucose, blood gas/bicarbonate, lactate, ammonia, AST/ALT, renal function, urinalysis/myoglobin;
continuous ECG/telemetry with repeated QTc assessment;
echocardiography and ventricular-function monitoring;
EEG for encephalopathy or seizure;
brain MRI for regression, focal findings, or unexplained neurologic progression.

Normal baseline acylcarnitines, amino acids, lactate, carnitine, or respiratory-chain studies do not exclude TDD. No validated enzyme assay or circulating biomarker exists. Western blot or research fibroblast functional testing can support loss of protein/function but is not the standard definitive test. (berat2021clinicalandbiological pages 12-17, dołega2024clinicalspectrumdiagnosis pages 4-7)

Genetic testing strategy

Use a neurodevelopmental/epilepsy, rhabdomyolysis/metabolic, cardiomyopathy/arrhythmia, or comprehensive Mendelian panel that explicitly includes TANGO2.
Require both sequence analysis and exon-level deletion/duplication analysis because multiexon deletions are common.
If panel testing is negative or phenotype is atypical, use trio WES or WGS with copy-number and structural-variant calling.
In a person with 22q11.2 deletion and suggestive features, sequence and assess copy number of the remaining TANGO2 allele.
Confirm phase/segregation in parents and apply ACMG/AMP criteria. RNA analysis may clarify splice variants.

Chromosomal microarray can detect a 22q11.2 deletion or sufficiently large TANGO2 deletion but may miss small exon-level or sequence variants. Karyotype and FISH are not adequate stand-alone tests; mtDNA and repeat-expansion testing are not indicated unless the differential independently warrants them.

Differential diagnosis

Consider fatty-acid oxidation disorders, mitochondrial cytopathies, glycogen-storage/metabolic myopathies, RYR1- and LPIN1-related rhabdomyolysis, PNKD, channelopathies/long-QT syndromes, Brugada syndrome, CPVT, epilepsy syndromes, and primary 22q11.2 deletion syndrome. TDD is distinguished by the combined neurodevelopmental–rhabdomyolysis–metabolic–arrhythmic phenotype and biallelic TANGO2 variants.

There are no universally validated clinical diagnostic criteria independent of molecular confirmation. No routine newborn biochemical screen exists. DNA-first newborn screening has been discussed because TDD lacks a reliable dried-blood-spot biochemical footprint, but evidence and implementation criteria remain insufficient. (dołega2024clinicalspectrumdiagnosis pages 1-4)

11. Outcome and prognosis

Population-level survival curves, 5-/10-year survival, and life expectancy are unavailable. Prognosis is highly variable and influenced by crisis frequency, early recognition, nutritional status, and access to intensive cardiac support.

Historical small cohorts demonstrate substantial mortality. In a 14-patient series, 5/14 died, four primarily from arrhythmia. In the severe cardiac-crisis cohort, 10/27 (37%) died, six from arrhythmia; these are referral-enriched estimates and overstate risk for all diagnosed patients. (miyake2022cardiaccrisescardiac pages 1-2, dines2019tango2expandingthe pages 5-6)

During severe cardiac crises, cardiomyopathy occurred in 70%, cardiac arrest in 74%, and VT in 78%. ECMO-supported survival from arrhythmia was reported in 5/6 supported patients, suggesting that aggressive escalation can be lifesaving. (miyake2022cardiaccrisescardiac pages 1-2)

Long-term morbidity includes intellectual and speech impairment, epilepsy, ataxia/spasticity/dystonia, mobility limitations, feeding dependence, recurrent hospitalization, and anxiety related to unpredictable crises. Acute kidney injury can follow severe rhabdomyolysis. Prognostic biomarkers beyond clinical trajectory, CK, QTc, ventricular function, and crisis burden are not validated.

12. Treatment and real-world implementation

There is no approved curative or genotype-replacing therapy. Care should be coordinated by metabolic genetics, cardiology/electrophysiology, neurology, endocrinology, nutrition, rehabilitation, and intensive care.

Baseline and preventive management

Regular meals and avoidance of prolonged fasting/dehydration.
Written emergency/sick-day plan and early hospital evaluation for fever, reduced intake, weakness, dark urine, seizure, or palpitations.
B-complex or multivitamin supplementation containing B5 and folate is increasingly used in practice, but dose, formulation, and efficacy are not trial-standardized.
Periodic ECG, thyroid testing, neurologic/developmental assessment, and individualized CK/cardiac surveillance.

Suggested MAXO concepts: genetic counseling; dietary management; vitamin supplementation; electrocardiographic monitoring; echocardiography; thyroid-function monitoring.

Acute metabolic/cardiac crisis

Provide prompt dextrose-containing fluids while restoring full enteral or parenteral nutrition, correct electrolytes, monitor CK/renal status, avoid QT-prolonging agents, and use continuous telemetry with frequent echocardiography. Glucose alone may be insufficient. Early nutrition, including micronutrients, is emphasized. (miyake2022cardiaccrisescardiac pages 8-9)

For malignant arrhythmia, reported strategies include IV magnesium, isoproterenol, overdrive atrial pacing, intensive electrolyte correction, and ECMO for refractory instability. Amiodarone and lidocaine were reported as potentially ineffective or aggravating in this specific crisis physiology; drug selection should be directed by a specialist TDD electrophysiology team rather than generic long-QT algorithms. (dołega2024clinicalspectrumdiagnosis pages 4-7, miyake2022cardiaccrisescardiac pages 8-9)

Suggested MAXO concepts: intravenous fluid therapy; glucose administration; electrolyte replacement; continuous cardiac monitoring; temporary cardiac pacing; extracorporeal membrane oxygenation; mechanical ventilation; renal-function monitoring.

Symptom-directed treatment

Epilepsy: levetiracetam or valproate have been used; selection should account for metabolic and cardiac safety.
Spasticity/dystonia: baclofen, clonazepam, botulinum toxin, plus physical/occupational therapy.
Hypothyroidism: levothyroxine.
Feeding/speech/mobility: nutrition support, gastrostomy when necessary, speech therapy, PT/OT, orthotics and assistive devices.
Heart failure during crisis: conventional ICU inotropes and heart-failure medications are individualized; rare severe cardiomyopathy has required transplantation. (dołega2024clinicalspectrumdiagnosis pages 4-7)

B-vitamin evidence

Vitamin B5/pantothenate—preclinical: In Drosophila, 2–4 mM B5 approximately doubled median starvation survival (~25 versus 12 hours), reduced heat-induced seizures by about 95%, prolonged seizure latency, and improved locomotor/behavioral measures. It restored ER-to-Golgi transport toward control rates in human TANGO2-deficient fibroblasts. The study’s abstract states: “vitamin B5 specifically improves multiple defects associated with TANGO2 loss-of-function in Drosophila and rescues membrane trafficking defects in human cells.” (asadi2023vitaminb5a pages 6-8, asadi2023vitaminb5a pages 1-3)

Folate/B9—iPSC cardiomyocytes: High-dose folate “virtually abolishes arrhythmias” in patient-derived iPSC cardiomyocytes; methotrexate blocked the benefit, supporting a requirement for intracellular folate metabolism. Wild-type TANGO2 expression and CRISPR correction also rescued the electrophysiologic phenotype. Human clinical support is observational, not randomized. (xu2024folateasa pages 1-2)

The apparently different B5-versus-B9 findings likely reflect assay and tissue specificity: B5 was strongest for fly systemic/trafficking phenotypes, whereas B9 was strongest in cardiomyocyte electrophysiology. A B-complex strategy may therefore be more rational than assuming a single active vitamin, but efficacy, dose, and toxicity require prospective study.

Experimental therapies and trials

No interventional gene, cell, RNA, CRISPR, or controlled drug trial was identified. NCT05374616 is a recruiting observational natural-history and biorepository study at Baylor, planned enrollment 300, started May 2018, estimated completion January 2030; it tracks metabolic/cardiac crises and collects blood, saliva, and fibroblasts. URL: https://clinicaltrials.gov/study/NCT05374616. (NCT05374616 chunk 1)

No TDD-specific pharmacogenomic rule is established.

13. Prevention

Primary prevention of inherited disease: impossible after conception through lifestyle modification. Options for at-risk families include carrier testing, partner testing, preimplantation genetic testing, prenatal diagnosis, donor gametes, and informed reproductive planning.

Secondary prevention: cascade testing of siblings/relatives and molecular diagnosis before a first crisis; targeted testing in symptomatic people with 22q11.2 deletion; possible future DNA-first newborn screening. Population newborn screening is not currently established. (owlett2024multicenterappraisalof pages 1-3, dołega2024clinicalspectrumdiagnosis pages 1-4)

Tertiary prevention: avoid fasting/dehydration, institute sick-day plans, provide early nutrition and B-complex supplementation under clinical supervision, monitor QTc and thyroid function, treat seizures/movement disorders, and prepare rapid escalation pathways for pacing/ECMO. Vaccination according to routine schedules may indirectly reduce febrile illnesses but is not TDD-specific immunotherapy.

Genetic counseling should explain autosomal-recessive recurrence, variable expressivity, limitations of prognosis, and the need to test deletion/duplication as well as sequence variants.

14. Other species and natural disease

No naturally occurring veterinary TANGO2-deficiency syndrome or breed predisposition was established in the retrieved evidence. There is no transmission or zoonotic potential.

Orthologues/homologues have been studied in:

Drosophila melanogaster—NCBI Taxon 7227;
Danio rerio—Taxon 7955;
Mus musculus—Taxon 10090;
Caenorhabditis elegans—Taxon 6239;
yeast and bacterial homologues in comparative biochemical work.

Evolutionary conservation supports roles in lipid/endomembrane biology and possibly heme handling, but the homologues are not functionally identical. Orthologue-specific NCBI Gene and VBO identifiers were not verified in the retrieved records and should be sourced directly before database ingestion.

15. Model organisms and experimental systems

Drosophila

Loss-of-function flies reproduce starvation sensitivity, heat-induced seizure susceptibility, impaired climbing/locomotion, learning deficits, and altered behavior. B5 robustly rescues several phenotypes; B3 provides weaker rescue. Advantages are rapid whole-organism stress and supplementation assays; limitations include a non-mammalian heart and incomplete correspondence to human neurodevelopment. (asadi2023vitaminb5a pages 6-8, asadi2023vitaminb5a pages 1-3)

Zebrafish

Mutants show growth impairment, smaller myofibers, abnormal glycerolipid pathways, stress-induced skeletal-muscle injury, early lethality, and approximately 96% mortality by three months in one model. Tango2 localizes near SR, Golgi, and mitochondria. This model is well suited to rhabdomyolysis, lipidomics, environmental triggers, and high-throughput rescue studies, but does not reproduce every human cardiac/neurodevelopmental feature. (kim2023intrinsicandextrinsic pages 1-3, kim2023intrinsicandextrinsic pages 3-5)

Mouse

Reported knockout mice have relatively normal development, lifespan, and gross physiology, making them a poor constitutive phenocopy under standard conditions. Stress paradigms, tissue-specific knockouts, or sensitized backgrounds may be needed. (kim2023intrinsicandextrinsic pages 3-5, casey2022glycerolipiddefectsin pages 1-5)

Human cellular models

Patient fibroblasts and myoblasts permit trafficking, lipidomic, respiration, ROS, and nutrient-stress studies but may not model excitable tissues. Patient-derived iPSC cardiomyocytes reproduce electrophysiologic abnormalities and respond to wild-type gene replacement, CRISPR correction, and folate, making them the most disease-proximal current arrhythmia platform. (xu2024folateasa pages 1-2, heiman2022mitochondrialdysfunctionassociated pages 1-2)

No validated cerebral organoid, skeletal-muscle organoid, single-cell disease atlas, or spatial-transcriptomic model was identified through 2024.

Evidence-weighted conclusions

Established: TDD is a biallelic TANGO2 loss-of-function disorder with high-risk stress-triggered rhabdomyolysis and ventricular arrhythmia superimposed on a variable neurodevelopmental syndrome.
Strong clinical signal: QT prolongation is nearly universal during severe cardiac crises, and VT, cardiac arrest, cardiomyopathy, and mortality are common in crisis-enriched cohorts. (miyake2022cardiaccrisescardiac pages 1-2)
Best current mechanism: impaired lipid/acyl-CoA and membrane homeostasis with secondary stress-dependent mitochondrial and trafficking dysfunction; a simple primary respiratory-chain defect is inadequate. (berat2021clinicalandbiological pages 1-7, lujan2023defectsinlipid pages 1-2)
Most important recent therapeutic development: convergent B-vitamin rescue evidence—B5 for systemic/trafficking defects and B9 for cardiomyocyte arrhythmia—plus observational human protection. It is promising but not yet randomized-trial evidence. (asadi2023vitaminb5a pages 6-8, xu2024folateasa pages 1-2)
Knowledge gaps: true prevalence, penetrance by genotype, modifier genes, prospective treatment effects/doses, validated biomarkers, standardized acute protocols, and faithful mammalian models.

Key recent sources and URLs

Xu et al., June 2024, JCI Insight, “Folate as a potential treatment…” https://doi.org/10.1172/jci.insight.171005. (xu2024folateasa pages 1-2)
Owlett et al., June 2024, American Journal of Medical Genetics A, 22q11.2 screening appraisal: https://doi.org/10.1002/ajmg.a.63778. (owlett2024multicenterappraisalof pages 1-3)
Dołęga et al., August 2024, clinical review: https://doi.org/10.12775/qs.2024.21.54001. (dołega2024clinicalspectrumdiagnosis pages 1-4)
Asadi et al., 2023, vitamin B5 rescue: https://doi.org/10.1002/jimd.12579. (asadi2023vitaminb5a pages 6-8)
Lujan et al., March 2023, lipid homeostasis: https://doi.org/10.7554/eLife.85345. (lujan2023defectsinlipid pages 1-2)
Kim et al., September 2023, zebrafish/stress susceptibility: https://doi.org/10.1242/dmm.050092. (kim2023intrinsicandextrinsic pages 1-3)
Miyake et al., October 2022, cardiac crises: https://doi.org/10.1016/j.hrthm.2022.05.009. (miyake2022cardiaccrisescardiac pages 1-2)
Baylor natural-history study: https://clinicaltrials.gov/study/NCT05374616. (NCT05374616 chunk 1)

References

(heiman2022mitochondrialdysfunctionassociated pages 1-2): Paige Heiman, Al-Walid Mohsen, Anuradha Karunanidhi, Claudette St Croix, Simon Watkins, Erik Koppes, Richard Haas, Jerry Vockley, and Lina Ghaloul-Gonzalez. Mitochondrial dysfunction associated with tango2 deficiency. Scientific Reports, Feb 2022. URL: https://doi.org/10.1038/s41598-022-07076-9, doi:10.1038/s41598-022-07076-9. This article has 51 citations and is from a peer-reviewed journal.
(miyake2022cardiaccrisescardiac pages 1-2): Christina Y. Miyake, Erica J. Lay, Cheyenne M. Beach, Scott R. Ceresnak, Caridad M. Delauz, Taylor S. Howard, Christopher M. Janson, Kate Jardine, Prince J. Kannankeril, Maina Kava, Jeffrey J. Kim, Leonardo Liberman, Scott L. Macicek, Tam Dam Pham, Terry Robertson, Santiago O. Valdes, Gregory Webster, Sara B. Stephens, Diana M. Milewicz, Mahshid Azamian, Saad A. Ehsan, Kimberly M. Houck, Claudia Soler-Alfonso, Kevin E. Glinton, Mustafa Tosur, Na Li, Weiyi Xu, Seema R. Lalani, and Lilei Zhang. Cardiac crises: cardiac arrhythmias and cardiomyopathy during tango2 deficiency related metabolic crises. Heart Rhythm, 19:1673-1681, Oct 2022. URL: https://doi.org/10.1016/j.hrthm.2022.05.009, doi:10.1016/j.hrthm.2022.05.009. This article has 37 citations and is from a peer-reviewed journal.
(berat2021clinicalandbiological pages 1-7): Claire‐Marine Bérat, Sebastian Montealegre, Arnaud Wiedemann, Malou Le Corronc Nuzum, Amélie Blondel, Hugo Debruge, Aline Cano, Brigitte Chabrol, Célia Hoebeke, Michel Polak, Athanasia Stoupa, François Feillet, Stéphanie Torre, Nathalie Boddaert, Henri Bruel, Magalie Barth, Lena Damaj, Marie‐Thérèse Abi‐Wardé, Alexandra Afenjar, Jean‐François Benoist, Marine Madrange, Laure Caccavelli, Perrine Renard, Arnaud Hubas, Patrick Nusbaum, Clément Pontoizeau, Stéphanie Gobin, Peter van Endert, Chris Ottolenghi, Alice Maltret, and Pascale de Lonlay. Clinical and biological characterization of 20 patients with tango2 deficiency indicates novel triggers of metabolic crises and no primary energetic defect. Sep 2020. URL: https://doi.org/10.1002/jimd.12314, doi:10.1002/jimd.12314. This article has 43 citations and is from a peer-reviewed journal.
(kim2023intrinsicandextrinsic pages 1-3): Euri S. Kim, Jennifer G. Casey, Brian S. Tao, Arian Mansur, Nishanthi Mathiyalagan, E. Diane Wallace, Brandie M. Ehrmann, and Vandana A. Gupta. Intrinsic and extrinsic regulation of rhabdomyolysis susceptibility by tango2. Disease Models & Mechanisms, Sep 2023. URL: https://doi.org/10.1242/dmm.050092, doi:10.1242/dmm.050092. This article has 14 citations and is from a domain leading peer-reviewed journal.
(lujan2023defectsinlipid pages 1-2): Agustin Leonardo Lujan, Ombretta Foresti, Conor Sugden, Nathalie Brouwers, Alex Mateo Farre, Alessio Vignoli, Mahshid Azamian, Alicia Turner, Jose Wojnacki, and Vivek Malhotra. Defects in lipid homeostasis reflect the function of tango2 in phospholipid and neutral lipid metabolism. eLife, Mar 2023. URL: https://doi.org/10.7554/elife.85345, doi:10.7554/elife.85345. This article has 31 citations and is from a domain leading peer-reviewed journal.
(asadi2023vitaminb5a pages 6-8): Paria Asadi, Miroslav P. Milev, Djenann Saint‐Dic, Chiara Gamberi, and Michael Sacher. Vitamin b5, a coenzyme a precursor, rescues tango2 deficiency disease‐associated defects in drosophila and human cells. Journal of Inherited Metabolic Disease, 46:358-368, Dec 2023. URL: https://doi.org/10.1002/jimd.12579, doi:10.1002/jimd.12579. This article has 45 citations and is from a peer-reviewed journal.
(xu2024folateasa pages 1-2): Weiyi Xu, Yingqiong Cao, Sara B. Stephens, Maria Jose Arredondo, Yifan Chen, William Perez, Liang Sun, Andy C. Yu, Jean J. Kim, Seema R. Lalani, Na Li, Frank T. Horrigan, Francisco Altamirano, Xander H.T. Wehrens, Christina Y. Miyake, and Lilei Zhang. Folate as a potential treatment for lethal ventricular arrhythmias in tango2-deficiency disorder. JCI Insight, Jun 2024. URL: https://doi.org/10.1172/jci.insight.171005, doi:10.1172/jci.insight.171005. This article has 10 citations and is from a domain leading peer-reviewed journal.
(asadi2023vitaminb5a pages 8-9): Paria Asadi, Miroslav P. Milev, Djenann Saint‐Dic, Chiara Gamberi, and Michael Sacher. Vitamin b5, a coenzyme a precursor, rescues tango2 deficiency disease‐associated defects in drosophila and human cells. Journal of Inherited Metabolic Disease, 46:358-368, Dec 2023. URL: https://doi.org/10.1002/jimd.12579, doi:10.1002/jimd.12579. This article has 45 citations and is from a peer-reviewed journal.
(OpenTargets Search: TANGO2 deficiency disorder-TANGO2): Open Targets Query (TANGO2 deficiency disorder-TANGO2, 1 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(mingirulli2020clinicalpresentationand pages 2-3): Nadja Mingirulli, Angela Pyle, Denisa Hathazi, Charlotte L. Alston, Nicolai Kohlschmidt, Gina O'Grady, Leigh Waddell, Frances Evesson, Sandra B. T. Cooper, Christian Turner, Jennifer Duff, Ana Topf, Delia Yubero, Cristina Jou, Andrés Nascimento, Carlos Ortez, Angels García‐Cazorla, Claudia Gross, Maria O'Callaghan, Saikat Santra, Maryanne A. Preece, Michael Champion, Sergei Korenev, Efsthatia Chronopoulou, Majumdar Anirban, Germaine Pierre, Daniel McArthur, Kyle Thompson, Placido Navas, Antonia Ribes, Frederic Tort, Agatha Schlüter, Aurora Pujol, Raquel Montero, Georgia Sarquella, Hanns Lochmüller, Cecilia Jiménez‐Mallebrera, Robert W. Taylor, Rafael Artuch, Janbernd Kirschner, Sarah C. Grünert, Andreas Roos, and Rita Horvath. Clinical presentation and proteomic signature of patients with tango2 mutations. Journal of Inherited Metabolic Disease, 43:297-308, Aug 2019. URL: https://doi.org/10.1002/jimd.12156, doi:10.1002/jimd.12156. This article has 55 citations and is from a peer-reviewed journal.
(berat2021clinicalandbiological pages 12-17): Claire‐Marine Bérat, Sebastian Montealegre, Arnaud Wiedemann, Malou Le Corronc Nuzum, Amélie Blondel, Hugo Debruge, Aline Cano, Brigitte Chabrol, Célia Hoebeke, Michel Polak, Athanasia Stoupa, François Feillet, Stéphanie Torre, Nathalie Boddaert, Henri Bruel, Magalie Barth, Lena Damaj, Marie‐Thérèse Abi‐Wardé, Alexandra Afenjar, Jean‐François Benoist, Marine Madrange, Laure Caccavelli, Perrine Renard, Arnaud Hubas, Patrick Nusbaum, Clément Pontoizeau, Stéphanie Gobin, Peter van Endert, Chris Ottolenghi, Alice Maltret, and Pascale de Lonlay. Clinical and biological characterization of 20 patients with tango2 deficiency indicates novel triggers of metabolic crises and no primary energetic defect. Sep 2020. URL: https://doi.org/10.1002/jimd.12314, doi:10.1002/jimd.12314. This article has 43 citations and is from a peer-reviewed journal.
(owlett2024multicenterappraisalof pages 1-3): Laura D. Owlett, Bianca Zapanta, Sarah E. Sandkuhler, Elizabeth G. Ames, Scott E. Hickey, Samuel J. Mackenzie, and Joshua K. Meisner. Multicenter appraisal of comorbid tango2 deficiency disorder in patients with 22q11.2 deletion syndrome. American Journal of Medical Genetics Part A, Jun 2024. URL: https://doi.org/10.1002/ajmg.a.63778, doi:10.1002/ajmg.a.63778. This article has 4 citations.
(kim2023intrinsicandextrinsic pages 3-5): Euri S. Kim, Jennifer G. Casey, Brian S. Tao, Arian Mansur, Nishanthi Mathiyalagan, E. Diane Wallace, Brandie M. Ehrmann, and Vandana A. Gupta. Intrinsic and extrinsic regulation of rhabdomyolysis susceptibility by tango2. Disease Models & Mechanisms, Sep 2023. URL: https://doi.org/10.1242/dmm.050092, doi:10.1242/dmm.050092. This article has 14 citations and is from a domain leading peer-reviewed journal.
(asadi2023vitaminb5a pages 1-3): Paria Asadi, Miroslav P. Milev, Djenann Saint‐Dic, Chiara Gamberi, and Michael Sacher. Vitamin b5, a coenzyme a precursor, rescues tango2 deficiency disease‐associated defects in drosophila and human cells. Journal of Inherited Metabolic Disease, 46:358-368, Dec 2023. URL: https://doi.org/10.1002/jimd.12579, doi:10.1002/jimd.12579. This article has 45 citations and is from a peer-reviewed journal.
(NCT05374616 chunk 1): Seema Lalani. Natural History Study and Establishment of a Biorepository-TANGO2-related Disorder. Baylor College of Medicine. 2018. ClinicalTrials.gov Identifier: NCT05374616
(dines2019tango2expandingthe pages 5-6): Jennifer N. Dines, Katie Golden-Grant, Amy LaCroix, Alison M. Muir, Dianne Laboy Cintrón, Kirsty McWalter, Megan T. Cho, Angela Sun, J. Lawrence Merritt, Jenny Thies, Dmitriy Niyazov, Barbara Burton, Katherine Kim, Leah Fleming, Rachel Westman, Peter Karachunski, Joline Dalton, Alice Basinger, Can Ficicioglu, Ingo Helbig, Manuela Pendziwiat, Hiltrud Muhle, Katherine L. Helbig, Almuth Caliebe, René Santer, Kolja Becker, Sharon Suchy, Ganka Douglas, Francisca Millan, Amber Begtrup, Kristin G. Monaghan, and Heather C. Mefford. Tango2: expanding the clinical phenotype and spectrum of pathogenic variants. Genetics in Medicine, 21:601-607, Mar 2019. URL: https://doi.org/10.1038/s41436-018-0137-y, doi:10.1038/s41436-018-0137-y. This article has 67 citations and is from a highest quality peer-reviewed journal.
(mingirulli2020clinicalpresentationand pages 1-2): Nadja Mingirulli, Angela Pyle, Denisa Hathazi, Charlotte L. Alston, Nicolai Kohlschmidt, Gina O'Grady, Leigh Waddell, Frances Evesson, Sandra B. T. Cooper, Christian Turner, Jennifer Duff, Ana Topf, Delia Yubero, Cristina Jou, Andrés Nascimento, Carlos Ortez, Angels García‐Cazorla, Claudia Gross, Maria O'Callaghan, Saikat Santra, Maryanne A. Preece, Michael Champion, Sergei Korenev, Efsthatia Chronopoulou, Majumdar Anirban, Germaine Pierre, Daniel McArthur, Kyle Thompson, Placido Navas, Antonia Ribes, Frederic Tort, Agatha Schlüter, Aurora Pujol, Raquel Montero, Georgia Sarquella, Hanns Lochmüller, Cecilia Jiménez‐Mallebrera, Robert W. Taylor, Rafael Artuch, Janbernd Kirschner, Sarah C. Grünert, Andreas Roos, and Rita Horvath. Clinical presentation and proteomic signature of patients with tango2 mutations. Journal of Inherited Metabolic Disease, 43:297-308, Aug 2019. URL: https://doi.org/10.1002/jimd.12156, doi:10.1002/jimd.12156. This article has 55 citations and is from a peer-reviewed journal.
(sandkuhler2026crossspeciesevaluationof pages 15-16): Sarah E Sandkuhler, Kayla S Youngs, Laura Owlett, Monica B Bandora, Aaliya Naaz, Euri S Kim, Lili Wang, Andrew P Wojtovich, Vandana A Gupta, Michael Sacher, and Samuel J Mackenzie. Heme’s relevance genuine? re-visiting the roles of tango2 homologs including hrg-9 and hrg-10 in c. elegans. Apr 2026. URL: https://doi.org/10.7554/elife.105418, doi:10.7554/elife.105418.
(miyake2022cardiaccrisescardiac pages 8-9): Christina Y. Miyake, Erica J. Lay, Cheyenne M. Beach, Scott R. Ceresnak, Caridad M. Delauz, Taylor S. Howard, Christopher M. Janson, Kate Jardine, Prince J. Kannankeril, Maina Kava, Jeffrey J. Kim, Leonardo Liberman, Scott L. Macicek, Tam Dam Pham, Terry Robertson, Santiago O. Valdes, Gregory Webster, Sara B. Stephens, Diana M. Milewicz, Mahshid Azamian, Saad A. Ehsan, Kimberly M. Houck, Claudia Soler-Alfonso, Kevin E. Glinton, Mustafa Tosur, Na Li, Weiyi Xu, Seema R. Lalani, and Lilei Zhang. Cardiac crises: cardiac arrhythmias and cardiomyopathy during tango2 deficiency related metabolic crises. Heart Rhythm, 19:1673-1681, Oct 2022. URL: https://doi.org/10.1016/j.hrthm.2022.05.009, doi:10.1016/j.hrthm.2022.05.009. This article has 37 citations and is from a peer-reviewed journal.
(dołega2024clinicalspectrumdiagnosis pages 4-7): Marcin Dołęga, Piotr Gacka, Olrgierd Dróżdż, Joanna Gołda, Julia Mężyk, and Aleksandra Snopkowska. Clinical spectrum, diagnosis, and management of tango2 deficiency disorder: a comprehensive review. Quality in Sport, 21:54001, Aug 2024. URL: https://doi.org/10.12775/qs.2024.21.54001, doi:10.12775/qs.2024.21.54001. This article has 2 citations.
(dołega2024clinicalspectrumdiagnosis pages 1-4): Marcin Dołęga, Piotr Gacka, Olrgierd Dróżdż, Joanna Gołda, Julia Mężyk, and Aleksandra Snopkowska. Clinical spectrum, diagnosis, and management of tango2 deficiency disorder: a comprehensive review. Quality in Sport, 21:54001, Aug 2024. URL: https://doi.org/10.12775/qs.2024.21.54001, doi:10.12775/qs.2024.21.54001. This article has 2 citations.
(casey2022glycerolipiddefectsin pages 1-5): Jennifer G Casey, Euri S Kim, Brian S Tao, Arian Mansur, E. Diane Wallace, and Vandana A Gupta. Glycerolipid defects in skeletal muscle contribute to rhabdomyolysis in tango2 deficiency. bioRxiv, Nov 2022. URL: https://doi.org/10.1101/2022.11.12.516274, doi:10.1101/2022.11.12.516274. This article has 1 citations.

Artifacts

Edison artifact artifact-00

Ask OpenScientist

OpenScientist Report

Inheritance

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Environmental Factors

Diagnosis

Progression

Prevalence

Differential Diagnoses

Clinical Trials

Experimental Models

Animal Models

Source YAML

References & Deep Research

References

Deep Research

TANGO2 Deficiency Disorder: Disease-Characteristics Research Report

Executive summary

1. Disease information

Definition and identifiers

2. Etiology, risk, protection, and gene–environment interaction

Causal factors

Genetic risk factors

Environmental and lifestyle risk factors

Protective factors

Gene–environment causal interaction

3. Phenotypes

Core phenotype frequencies and characteristics

4. Genetic and molecular information

5. Environmental information

6. Mechanism and pathophysiology

Current mechanistic model

Localization and protein function

Suggested ontology annotations

Molecular profiling and advanced technologies

7. Anatomical structures affected

8. Temporal development

9. Inheritance and population

10. Diagnostics

When to suspect TDD

Acute clinical testing

Genetic testing strategy

Differential diagnosis

11. Outcome and prognosis

12. Treatment and real-world implementation

Baseline and preventive management

Acute metabolic/cardiac crisis

Symptom-directed treatment

B-vitamin evidence

Experimental therapies and trials

13. Prevention

14. Other species and natural disease

15. Model organisms and experimental systems

Drosophila

Zebrafish

Mouse

Human cellular models

Evidence-weighted conclusions

Key recent sources and URLs

Artifacts