Dilated Cardiomyopathy 1BB

Genetic MONDO:0013030 Pathograph 31 Show in embeddings browser Cardiovascular Disease Genetic Disorder

DSG2-related familial isolated dilated cardiomyopathy (CMD1BB) is the dilated, left-dominant or biventricular presentation of desmoglein-2 deficiency. Desmoglein-2 is the principal desmosomal cadherin of the cardiomyocyte intercalated disc, where the desmosome and the adherens junction are intermingled as the area composita. Loss of desmoglein-2 destabilises that junction, mechanically uncouples adjacent cardiomyocytes, and permits myocyte necrosis with aseptic inflammation and fibrofatty replacement; the surviving ventricle dilates and loses contractile function. The entry is scoped to the presentation in which chamber dilation and systolic failure dominate the clinical picture rather than isolated right ventricular arrhythmogenic disease. Allele dose is the principal determinant of severity: heterozygous carriers typically present in adulthood with a milder, frequently event-free course, whereas biallelic (homozygous, compound heterozygous, or hemizygous) loss of function gives early-onset biventricular disease that can reach transplantation.

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Classifications

Harrison's Part

Mechanistic Nosology

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Inheritance

Autosomal dominant HP:0000006

The majority of DSG2-related disease is transmitted as an autosomal dominant trait with reduced, age-related and exercise-modulated penetrance. Heterozygous carriers of the Chinese p.Phe531Cys founder variant remained free of end-stage heart failure and composite events over follow-up, which is the clearest available statement of how mild the monoallelic course can be.

Autosomal dominant inheritance Penetrance: INCOMPLETE

Show evidence (2 references)

PMID:16773573 SUPPORT Human Clinical

"It is inherited as an autosomal dominant disease with reduced penetrance, although autosomal recessive forms of the disease also occur."

States the dominant-with-reduced-penetrance mode and simultaneously records that recessive forms exist, which is the contrast this entry curates in the second Inheritance block.

PMID:41662985 SUPPORT Human Clinical

"Compound and homozygous variant carriers exhibited significantly higher incidences of end-stage heart failure and composite events, whereas single heterozygous variant carriers remained event-free (all P < .05)."

Quantifies the mildness of the monoallelic course in a 91-subject founder variant cohort, supporting incomplete penetrance in heterozygotes.

Autosomal recessive HP:0000007

A minority of cases are recessive. Biallelic loss of function - homozygous, compound heterozygous, or hemizygous where a point mutation is unmasked by a large deletion of the second allele - produces earlier-onset, biventricular disease, and the obligate heterozygous parents are typically unaffected, which is why these families present without an apparent family history.

Autosomal recessive inheritance

Show evidence (1 reference)

PMID:33917638 SUPPORT Human Clinical

"In conclusion, a recessive inheritance pattern is likely for both cases, which might contribute to the hidden medical history in both families."

Establishes recessive inheritance in two index patients and explains why such families lack a family history, which is the diagnostic trap.

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Subtypes

Biallelic DSG2 loss of function (early onset)

Homozygous, compound heterozygous, or hemizygous loss of DSG2 function. Presents earlier, with more ECG abnormality and more biventricular involvement, and progresses to end-stage heart failure and transplantation far more often than the monoallelic form. Obligate heterozygous relatives are typically unaffected, so these families often present without a family history and the disease can be mistaken for sporadic myocarditis.

Show evidence (3 references)

PMID:41662985 SUPPORT Human Clinical

"Homozygous variant carriers experienced significantly earlier MVA than compound (P = .013) and single heterozygous variant carriers (P < .001)"

Direct evidence for the allele-dose gradient in timing of malignant ventricular arrhythmia.

PMID:33917638 SUPPORT Human Clinical

"Of note, this genetic strategy revealed a homozygous splice site mutation (DSG2-c.378+1G>T) in the first patient and a nonsense mutation (DSG2-p.L772X) in combination with a large deletion in DSG2 in the second one."

Documents both the homozygous and the hemizygous (point mutation unmasked by deletion) routes to biallelic loss described in this subtype.

PMID:40956261 SUPPORT Human Clinical

"Homozygous variants in DSG2, a desmosomal protein, are associated with a severe form of biventricular arrhythmogenic cardiomyopathy (ACM)."

States the homozygous-to-severe-biventricular association that defines this subtype.

Heterozygous DSG2 variant (adult onset)

A single pathogenic DSG2 allele. Later onset, milder phenotype, and a relatively favourable prognosis; in the Chinese founder-variant cohort single heterozygotes remained free of end-stage heart failure and composite events entirely. Penetrance is incomplete and strongly modified by exercise exposure.

Show evidence (1 reference)

PMID:41662985 SUPPORT Human Clinical

"Single heterozygous variant carriers held a less severe phenotype and relatively favorable prognosis, whereas compound and homozygous variant carriers held an advanced phenotype and poorer prognosis."

States the monoallelic-versus-biallelic prognostic contrast that defines these two subtypes.

Discussions and Knowledge Gaps

Does plakoglobin actually redistribute to the nucleus in DSG2-related cardiomyopathy, or is the reduced junctional plakoglobin signal an artefact of epitope masking?

KNOWLEDGE GAP dsg2_plakoglobin_epitope_vs_relocalization

Attached to

pathophysiology#Plakoglobin Nuclear Redistribution pathophysiology#Canonical Wnt Signaling Suppression

Reduced junctional plakoglobin immunofluorescence has been proposed as a diagnostic marker and as the mechanistic link between desmosomal disruption and fibrofatty replacement. That interpretation rests on the signal reflecting genuine protein relocalization. Work in desmoglein-2 mutant mice and human ARVC biopsies found the reduced signal only with one antibody against one epitope and not with three others, concluding that epitope accessibility rather than relocalization explains it. If that is right, the Wnt-suppression arm of the mechanism loses its principal human observational support and the fibrofatty pathway needs a different explanation - for which the mTOR-PPAR-alpha metabolic route and TGF-beta/Smad3 fibrogenesis curated on the replacement node are the leading candidates. The entry records the canonical mechanism and its contradiction side by side rather than choosing.

Proposed experiments

Epitope-independent quantification of plakoglobin compartmentalisation in DSG2 myocardium

dsg2_plakoglobin_epitope_independent_quantification

Quantify nuclear versus junctional plakoglobin in DSG2-variant human myocardium using a method that does not depend on antibody epitope accessibility - for example subcellular fractionation with mass spectrometry, or tagged-allele imaging in isogenic iPSC-derived cardiomyocytes - alongside a readout of canonical Wnt target gene expression.

Would support

pathophysiology#Plakoglobin Nuclear Redistribution pathophysiology#Canonical Wnt Signaling Suppression

Would refute

pathophysiology#Plakoglobin Nuclear Redistribution pathophysiology#Canonical Wnt Signaling Suppression

Supporting outcome

Nuclear plakoglobin is increased and canonical Wnt target gene expression is reduced in DSG2-deficient cardiomyocytes by a method independent of antibody epitope accessibility.

Refuting outcome

Total and nuclear plakoglobin are unchanged and Wnt target genes are not suppressed, indicating the immunofluorescence finding is an epitope artefact and the adipogenic program arises by another route.

Is the dilated, left-dominant DSG2 presentation curated here a distinct entity from right-dominant DSG2 arrhythmogenic cardiomyopathy, or one end of a single continuum?

KNOWLEDGE GAP dsg2_dilated_vs_right_dominant_boundary

Attached to

disease#Dilated Cardiomyopathy 1BB pathophysiology#Biventricular Remodeling and Chamber Dilation

CMD1BB exists as an OMIM and MONDO concept and is curated here on that basis, but the genotype-defined cohorts do not separate cleanly: in the pooled series 38.1% were right-dominant and 31.2% biventricular, and in the founder-variant cohort three quarters had right ventricular dilatation while half had biventricular involvement. No mechanism has been identified that determines which ventricle dominates in a given DSG2 carrier. Until one is, the split between this entry and Arrhythmogenic_Right_Ventricular_Cardiomyopathy is a phenotypic and nosological convenience rather than a mechanistic boundary, and readers should treat it as such.

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Pathophysiology

DSG2 Loss of Function at the Cardiac Desmosome

Pathogenic DSG2 alleles reduce the amount of functional desmoglein-2 available to the cardiomyocyte desmosome. Truncating, splice and deletion alleles remove the protein outright; extracellular-domain missense alleles produce protein that is still incorporated into the junction but cannot perform calcium-dependent trans-adhesion to desmocollin-2, so the effect is dominant-negative and dose-dependent. This is the initiating molecular lesion of the entry.

cardiac muscle cell CL:0000746

DSG2 hgnc:3049

cadherin binding GO:0045296 ⇓ LOSS OF FUNCTION

desmosome GO:0030057

Downstream

Intercalated Disc Desmosome Destabilization Absent or non-adhesive desmoglein-2 leaves the intercalated disc unable to assemble structurally normal desmosomes.

Mutant DSG2 Protein Misfolding in the Endoplasmic Reticulum A branch taken only by misfolding missense alleles. The mutant protein is retained and recognised in the endoplasmic reticulum rather than reaching the junction, so this route is not available to null alleles that produce no protein at all.

Show evidence (2 references)

PMID:33949662 SUPPORT Human Clinical

"we identified a homozygous stop-gain mutations in DSG2 (c.C355T, p.R119X) that led to complete desmoglein-2 deficiency in a patient with severe biventricular heart failure"

Directly links a DSG2 null genotype to complete loss of the protein and to the biventricular failure phenotype this entry curates.

PMID:19635863 SUPPORT Model Organism

"Investigation of transgenic lines with different levels of transgene expression attested to a dose-dependent dominant-negative effect of the mutation."

Supports the dominant-negative, dose-dependent character of missense DSG2 alleles asserted in this node.

Intercalated Disc Desmosome Destabilization

Desmosomes at the intercalated disc are reduced in number, structurally abnormal, or absent, and the intercellular space at the desmosome and adherens-junction level widens. Because the cardiac intercalated disc is an area composita in which desmosomal and adherens-junction components are intermingled, the destabilisation is not confined to the desmosome proper; it also perturbs the junctional protein complexes that the sodium channel and gap junctions depend on. This node is the branch point of the entry.

cardiac muscle cell CL:0000746

desmosome organization GO:0002934 ↓ DECREASED

adherens junction GO:0005912

Animal models

Cardiomyocyte-specific Dsg2 knockout mouse Mouse recapitulates Reproduces the ultrastructural loss of intercalated disc desmosomes that is the central junctional lesion.

Downstream

Mechanical Uncoupling of Cardiomyocytes Loss of the load-bearing junction removes mechanical continuity between adjacent cardiomyocytes.

Sodium Current Reduction and Conduction Slowing Junctional destabilisation perturbs the Nav1.5 sodium channel complex that is co-located at the intercalated disc, independently of and earlier than any structural myocardial damage.

Plakoglobin Nuclear Redistribution Destabilisation of the junctional plaque is the proposed route by which plakoglobin becomes available to the nucleus. This edge is the contested arm of the entry - see the discussions block.

Cardiomyocyte NF-kappaB Activation Desmosomal disruption activates innate immune signalling within the cardiomyocyte itself, before and independently of any infiltrating inflammatory cell.

Connexin-43 Gap Junction Remodeling The mechanical junction and the gap junction share the intercalated disc and are interdependent, so loss of desmosomal anchorage is followed by mislocalisation and loss of connexin-43 from the disc.

Show evidence (3 references)

PMID:26085008 SUPPORT Model Organism

"Electron microscopy revealed absence of desmosome-like structures and regional loss of intercalated disc adhesion."

Direct ultrastructural demonstration that cardiomyocyte-specific Dsg2 loss abolishes desmosomes at the intercalated disc.

PMID:22764152 SUPPORT Model Organism

"Assessment by electron microscopy established that intercellular space widening at the desmosomes/adherens junctions occurred in Tg-NS/L mice before the onset of necrosis and fibrosis."

Establishes that junctional widening precedes cell death, so this node is genuinely upstream of the necrosis node rather than a consequence of it.

PMID:28764973 SUPPORT Human Clinical

"This suggests that the architecture of desmosomes is already disturbed in the early stages of DCM."

Human pediatric dilated cardiomyopathy tissue showing desmosomal architecture is disturbed early, supporting this node's placement upstream in a dilated rather than purely arrhythmogenic phenotype.

Mechanical Uncoupling of Cardiomyocytes

Adjacent cardiomyocytes are no longer mechanically coupled and the myocardium cannot distribute contractile load across the syncytium. Tissue-level force generation falls and the tissue becomes fragile under the repeated mechanical demand of contraction, which is why exercise is a disease modifier rather than an incidental exposure.

cardiac muscle cell CL:0000746

calcium-dependent cell-cell adhesion GO:0016339 ↓ DECREASED

Experimental models

DSG2 p.R119X patient-derived iPSC cardiomyocytes with isogenic correction IPSC DERIVED MODEL Human patient-derived tissue reproduces the mechanical failure that is the core of the entry's mechanism, and isogenic correction rescues it.

Downstream

Cardiomyocyte Necrosis Mechanically uncoupled myocytes detach and die under continued contractile load.

Show evidence (1 reference)

PMID:33949662 SUPPORT In Vitro

"Micro-force testing of three-dimensional self-organized tissue rings (SOTRs) revealed tissue fragility and a weak maximum force in SOTRs from R119X-iPSC-CMs."

Direct mechanical measurement in patient-derived human tissue showing that desmoglein-2 loss produces a fragile, weakly contracting tissue.

Sodium Current Reduction and Conduction Slowing

Sodium current density falls and action potential upstroke velocity is reduced, slowing conduction longitudinally and transversally and increasing arrhythmia inducibility. Crucially this occurs before necrosis and replacement fibrosis, so the arrhythmic substrate is not simply a scar phenomenon - it is an early, potentially reversible electrical consequence of junctional disruption. This is the mechanistic reason a DSG2 carrier can die suddenly with a structurally near-normal heart.

ventricular cardiac muscle cell CL:2000046

voltage-gated sodium channel activity GO:0005248 ↓ DECREASED

Downstream

Ventricular tachycardia Slowed conduction and increased arrhythmia inducibility give the ventricular tachyarrhythmias that dominate clinical presentation.

Show evidence (2 references)

PMID:22764152 SUPPORT Model Organism

"A reduced action potential (AP) upstroke velocity due to a lower Na(+) current density was also observed at this stage of the disease."

Direct electrophysiological measurement of the reduced sodium current that defines this node.

PMID:22764152 SUPPORT Model Organism

"Intercellular space widening at the level of the intercalated disc (desmosomes/adherens junctions) and a concomitant reduction in AP upstroke velocity as a consequence of lower Na(+) current density lead to slowed conduction and increased arrhythmia susceptibility at disease stages preceding the..."

Establishes the pre-structural timing that makes this node an independent arrhythmic mechanism rather than a downstream scar effect.

Connexin-43 Gap Junction Remodeling

Connexin-43, the principal ventricular gap junction protein, is mislocalised and reduced at the intercalated disc once desmosomal anchorage fails. This is the electrical-coupling counterpart of the sodium-current node: the two together explain why conduction is abnormal in DSG2 disease before there is enough scar to account for it. Stabilising desmoglein-2 binding restores connexin-43 localisation and abolishes the conduction irregularity, which is what makes this a consequence of the desmosomal lesion rather than an independent finding.

ventricular cardiac muscle cell CL:2000046

gap junction assembly GO:0016264 ↓ DECREASED

connexin-43 gap junction at the intercalated disc GO:0005921

Downstream

Ventricular tachycardia Reduced gap junctional coupling slows and disperses conduction, which with the sodium-current deficit supplies the re-entrant substrate for ventricular tachyarrhythmia before structural scar is established.

Show evidence (3 references)

PMID:32376797 SUPPORT In Vitro

"Dsg2-LP rescued connexin-43 mislocalization and conduction irregularities in response to impaired cardiomyocyte cohesion."

Shows connexin-43 mislocalisation is downstream of impaired desmoglein-2-dependent cohesion and is reversible by restoring that binding.

PMID:26085008 SUPPORT Model Organism

"All animals developed AC during postnatal growth with pronounced chamber dilation, calcifying cardiomyocyte necrosis, aseptic inflammation, interstitial and focal replacement fibrosis, and conduction defects with altered connexin 43 distribution."

In vivo confirmation in the cardiomyocyte-specific Dsg2 knockout that altered connexin-43 distribution accompanies the conduction defect.

PMID:15851108 SUPPORT INDIRECT Human Clinical

"Connexin43 expression at intercellular junctions was reduced significantly in both right and left ventricles in all patients with Naxos disease."

Human myocardial demonstration that a desmosomal lesion reduces junctional connexin-43 in both ventricles. Graded INDIRECT because the lesion studied is a plakoglobin deletion, not a DSG2 variant, so it supports the desmosomal class and is extrapolated to DSG2 here.

Plakoglobin Nuclear Redistribution

In the canonical model of desmosomal cardiomyopathy, plaque destabilisation releases plakoglobin from the junction and it accumulates in the nucleus. This node is retained because it is the first step of the mechanism most often invoked for fibrofatty replacement, but the evidence base is genuinely contested and the node is curated with its refuting evidence attached rather than asserted cleanly.

cardiac muscle cell CL:0000746

protein localization to nucleus GO:0034504 ↑ INCREASED

Downstream

Canonical Wnt Signaling Suppression Nuclear plakoglobin competes with beta-catenin for Tcf/Lef transcription factors, so the canonical Wnt output falls.

Show evidence (2 references)

PMID:16823493 SUPPORT INDIRECT In Vitro

"We show suppression of DP expression leads to nuclear localization of the desmosomal protein plakoglobin and a 2-fold reduction in canonical Wnt/beta-catenin signaling through Tcf/Lef1 transcription factors."

The founding demonstration that losing a desmosomal plaque protein sends plakoglobin to the nucleus. Graded INDIRECT because it was obtained by suppressing desmoplakin, not desmoglein-2; it supports the mechanism for the desmosomal class and is extrapolated to DSG2 here rather than shown in it.

PMID:26676851 REFUTE Model Organism

"Reduced plakoglobin staining in intercalated discs of heart tissue from human ARVC patients and in a murine ARVC model is caused by alterations in epitope accessibility and not by protein relocalization."

Directly contradicts the redistribution interpretation of the standard immunofluorescence finding, and does so in desmoglein-2 mutant mice specifically. Curated as REFUTE so the node carries its own contradiction.

Canonical Wnt Signaling Suppression

Canonical Wnt/beta-catenin output through Tcf/Lef falls, de-repressing an adipogenic and fibrogenic transcriptional program in the cardiomyocyte lineage. This is the transcriptional route to fibrofatty replacement, and it is the arm of the entry whose supporting human observation is disputed - see the discussions block.

cardiac muscle cell CL:0000746

Wnt signaling pathway GO:0016055 ↓ DECREASED fat cell differentiation GO:0045444 ↑ INCREASED

Downstream

Fibrofatty Myocardial Replacement De-repression of the adipogenic and fibrogenic program is the proposed route to fatty replacement. Marked INDIRECT because the DSG2-specific link rests on extrapolation from desmoplakin work.

Show evidence (1 reference)

PMID:16823493 SUPPORT INDIRECT In Vitro

"The ensuing phenotype is increased expression of adipogenic and fibrogenic genes and accumulation of fat droplets."

Connects the Wnt suppression to the adipogenic and fibrogenic program that this node asserts. INDIRECT for the same desmoplakin-not-desmoglein reason.

Cardiomyocyte NF-kappaB Activation

NF-kappaB signalling is activated in the desmosome-deficient cardiomyocyte under basal conditions, without an external immune stimulus. This cell-autonomous innate immune response is causal for myocardial injury, contractile dysfunction and arrhythmia in the Dsg2 mutant mouse, which is what makes inflammation a driver of the disease rather than a reaction to it.

cardiac muscle cell CL:0000746

positive regulation of canonical NF-kappaB signal transduction GO:0043123 ↑ INCREASED

Downstream

CCR2+ Macrophage Recruitment Cardiomyocyte NF-kappaB signalling is what mobilises CCR2-expressing macrophages into the affected myocardium.

Show evidence (1 reference)

PMID:38564300 SUPPORT Model Organism

"We found that NFκB signaling in cardiac myocytes drives myocardial injury, contractile dysfunction, and arrhythmias in Dsg2mut/mut mice."

Genetic demonstration in a Dsg2 mutant model that cardiomyocyte NF-kappaB signalling is causal for injury, dysfunction and arrhythmia.

CCR2+ Macrophage Recruitment

CCR2-expressing macrophages are mobilised into the affected myocardium, where they themselves mediate myocardial injury and arrhythmia. Their presence is the reason DSG2 disease can present as an apparent myocarditis and be mistaken for an infectious or granulomatous myocardial disease.

CCR2-expressing macrophage CL:0000235

macrophage chemotaxis GO:0048246 ↑ INCREASED

Downstream

Cardiomyocyte Necrosis Recruited CCR2+ macrophages mediate the myocardial injury.

Progressive Contractile Dysfunction and Heart Failure Inflammation depresses contractility in viable muscle, so contractile failure is not solely explained by loss of myocardium.

Show evidence (1 reference)

PMID:38564300 SUPPORT Model Organism

"NFκB signaling in cardiac myocytes mobilizes macrophages expressing C-C motif chemokine receptor-2 (CCR2+ cells) to affected areas within the heart, where they mediate myocardial injury and arrhythmias."

Establishes both that the CCR2+ population is recruited and that the recruited cells are themselves effectors of injury, which is this node.

Mutant DSG2 Protein Misfolding in the Endoplasmic Reticulum

The first step of a parallel, allele-specific route to fibrosis that does not run through adhesion loss. Certain missense DSG2 variants misfold in the endoplasmic reticulum and are recognised by the chaperone BiP rather than trafficking to the junction. Only alleles that make a protein can take this route, so it is unavailable to null alleles.

cardiac muscle cell CL:0000746

protein folding GO:0006457 ↓ DECREASED

endoplasmic reticulum GO:0005783

Downstream

PERK-ATF4 Endoplasmic Reticulum Stress Signaling BiP engagement by the misfolded cadherin triggers endoplasmic reticulum stress and activates the PERK-ATF4 branch of the unfolded protein response.

Show evidence (1 reference)

PMID:39227800 SUPPORT Model Organism

"Mechanistic investigations revealed that the variant DSG2-F536C protein underwent misfolding, leading to its recognition by BiP within the endoplasmic reticulum, which triggered endoplasmic reticulum stress, activated the PERK-ATF4 signaling pathway and increased ATF4 levels in cardiomyocytes."

States the misfolding and BiP recognition that define this node, and names the ER stress response as its consequence.

PERK-ATF4 Endoplasmic Reticulum Stress Signaling

Endoplasmic reticulum stress activates the PERK-ATF4 branch of the unfolded protein response and ATF4 levels rise in the cardiomyocyte. Pharmacological inhibition of PERK-ATF4 attenuates progressive fibrosis and systolic dysfunction in the corresponding knock-in mouse, so this node is causal for the fibrotic outcome rather than a bystander stress marker.

cardiac muscle cell CL:0000746

response to endoplasmic reticulum stress GO:0034976 ↑ INCREASED endoplasmic reticulum unfolded protein response GO:0030968 ↑ INCREASED

Downstream

Cardiomyocyte TGF-beta1 Production Raised ATF4 drives transcription of TGF-beta1 in the cardiomyocyte.

Show evidence (1 reference)

PMID:39227800 SUPPORT Model Organism

"Notably, inhibition of the PERK-ATF4 signaling attenuated progressive cardiac fibrosis and cardiac systolic dysfunction in Dsg2F536C/F536C mice."

Interventional evidence that this node is causally responsible for a share of the fibrosis and systolic dysfunction, not merely correlated with it.

Cardiomyocyte TGF-beta1 Production

The stressed cardiomyocyte secretes TGF-beta1, which activates neighbouring cardiac fibroblasts by paracrine signalling. This is what makes fibrosis a direct consequence of the mutant protein's folding behaviour rather than only a repair response to myocyte death.

cardiac muscle cell CL:0000746

transforming growth factor beta production GO:0071604 ↑ INCREASED

Downstream

Fibrofatty Myocardial Replacement Cardiomyocyte-derived TGF-beta1 activates cardiac fibroblasts and drives the fibrotic component of replacement.

Show evidence (1 reference)

PMID:39227800 SUPPORT Model Organism

"Increased ATF4 facilitated the expression of TGF-β1 in cardiomyocytes, thereby activating cardiac fibroblasts through paracrine signaling and ultimately promoting cardiac fibrosis in Dsg2F536C/F536C mice."

States that TGF-beta1 is expressed by the cardiomyocyte itself and acts on fibroblasts in a paracrine fashion, which is this node.

Cardiomyocyte Necrosis

Detached cardiomyocytes die by necrosis, with myocardial calcification in the DSG2 mouse. Necrosis - not apoptosis - is the initiating injury in this disease, and it is the event that both provokes the sterile inflammatory response and creates the defect that fibrofatty tissue fills.

cardiac muscle cell CL:0000746

cardiomyocyte necrosis GO:0008219 ↑ INCREASED

Animal models

Tg-NS Dsg2-N271S transgenic mouse Mouse recapitulates Identifies myocyte necrosis as the initiating injury and traces the sequence through inflammation to fibrous replacement.

Downstream

Aseptic Myocardial Inflammation Necrotic myocytes release damage signals that provoke a sterile inflammatory infiltrate.

Fibrofatty Myocardial Replacement Necrotic myocardium is repaired by fibrous and adipose tissue rather than by myocyte regeneration.

Show evidence (2 references)

PMID:19635863 SUPPORT Model Organism

"We demonstrate for the first time that myocyte necrosis is the key initiator of myocardial injury, triggering progressive myocardial damage, including an inflammatory response and massive calcification within the myocardium, followed by injury repair with fibrous tissue replacement, and..."

Names necrosis specifically as the initiating injury and places inflammation and fibrous replacement downstream of it.

PMID:26085008 SUPPORT Model Organism

Independent confirmation of calcifying cardiomyocyte necrosis in a cardiomyocyte-specific Dsg2 knockout.

Aseptic Myocardial Inflammation

A sterile inflammatory infiltrate occupies the injured myocardium. This is the substrate for the myocarditis-like hot phases that DSG2 carriers can present with and that are readily misdiagnosed as infectious myocarditis or cardiac sarcoidosis - a mimicry severe enough that a homozygous DSG2 case met four of five major criteria for isolated cardiac sarcoidosis.

macrophage CL:0000235

inflammatory response GO:0006954 ↑ INCREASED

Downstream

Fibrofatty Myocardial Replacement The inflammatory phase resolves into fibrous and fatty repair rather than restoration of contractile myocardium.

Show evidence (2 references)

PMID:26085008 SUPPORT Model Organism

Names aseptic inflammation as a feature of the cardiomyocyte-specific Dsg2 knockout myocardium.

PMID:40956261 SUPPORT Human Clinical

"Post-transplant histology showed no granulomas, but extensive fibrofatty replacement typically seen in ACM."

Human explant histology confirming that the inflammatory presentation which mimicked cardiac sarcoidosis was in fact the fibrofatty process of this disease, supporting the mimicry claim in this node's description.

Fibrofatty Myocardial Replacement

Lost myocardium is replaced by fibrous and adipose tissue. In DSG2 disease the fatty component has a metabolic contributor as well as a transcriptional one: cardiac Dsg2 deletion impairs mTOR-4EBP1-PPAR-alpha signalling and hence fatty acid beta-oxidation, so lipid accumulates in the myocardium. Fibrogenesis is driven through TGF-beta/Smad3 signalling. The resulting tissue is both non-contractile and electrically inhomogeneous.

fibroblast of cardiac tissue CL:0002548 adipocyte CL:0000136

transforming growth factor beta receptor signaling pathway GO:0007179 ↑ INCREASED extracellular matrix organization GO:0030198 ↑ INCREASED

Downstream

Biventricular Remodeling and Chamber Dilation Replacement of contractile myocardium by non-contractile tissue drives chamber dilation.

Ventricular tachycardia Fibrofatty tissue interposed between surviving myocyte bundles creates the re-entrant substrate for scar-related ventricular tachycardia.

Show evidence (2 references)

PMID:40019607 SUPPORT Model Organism

"SFRP4 knockdown markedly reduced myocardial fibrosis, ventricular compliance, and cardiac dilation in Dsg2-/- mice."

Interventional evidence in the Dsg2 knockout that the fibrotic and dilated phenotype is driven by an identifiable profibrotic signal rather than being passive scarring.

PMID:36815030 SUPPORT Model Organism

"We demonstrated that these phenotypes were caused by decline of fatty acid (FA) β-oxidation resulted from impaired mammalian target of rapamycin (mTOR) signaling."

Supports the metabolic contribution to myocardial lipid accumulation claimed in this node, distinct from the transcriptional adipogenesis route.

Biventricular Remodeling and Chamber Dilation

The ventricles dilate. In the presentation this entry curates, the left ventricle is involved either dominantly or together with the right, which is what distinguishes CMD1BB from the classical right-dominant arrhythmogenic picture. Biventricular involvement is the phenotype that predicts heart failure progression in DSG2 disease.

ventricular cardiac muscle cell CL:2000046

Animal models

Cardiomyocyte-specific Dsg2 knockout mouse Mouse recapitulates Develops pronounced chamber dilation with necrosis, inflammation and replacement fibrosis.

Downstream

Progressive Contractile Dysfunction and Heart Failure A dilated, fibrotically remodeled ventricle progressively loses systolic function.

Show evidence (2 references)

PMID:41067474 SUPPORT Human Clinical

"Patients with LTVAs had more severe right ventricular dysfunction, whereas those developing HF exhibited biventricular involvement."

Establishes that biventricular remodeling, not right-dominant disease, is the substrate for heart failure progression - the clinical rationale for separating this entry from the right-dominant parent.

PMID:40123482 SUPPORT Human Clinical

"Among the 81 individuals for whom both left ventricular ejection fraction and right ventricular fractional area change data were available at presentation, 29 (35.8%) had isolated right ventricular dysfunction, and 16 (19.8%) had biventricular dysfunction."

Quantifies how often DSG2/DSC2 disease presents with biventricular rather than isolated right ventricular dysfunction.

Progressive Contractile Dysfunction and Heart Failure

Systolic function declines and clinical heart failure supervenes. DSG2 and DSC2 carriers reach end-stage heart failure significantly more often than PKP2 carriers do, which is the principal prognostic difference between this entry and PKP2_Cardiomyopathy. Biallelic carriers reach this endpoint earlier and more frequently than heterozygotes.

Downstream

Congestive heart failure Falling systolic function manifests clinically as congestive heart failure.

Show evidence (2 references)

PMID:40123482 SUPPORT Human Clinical

"Compared with PKP2 patients, DSG2/DSC2 patients exhibited a significantly higher risk of end-stage heart failure (P<0.001)."

Direct comparative evidence for the prognostic distinction from the PKP2 entry asserted in this node.

PMID:33949662 SUPPORT Human Clinical

"Our findings confirm the presence of a desmoglein-2-deficient cardiomyopathy among clinically diagnosed dilated cardiomyopathies."

The clearest statement in the literature that desmoglein-2 deficiency belongs among the dilated cardiomyopathies, which is the identity claim of this entry.

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Pathograph

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Phenotypes

Dilated cardiomyopathy Cardiac HP:0001644

Course: PROGRESSIVE

Sequelae: Congestive heart failure

Show evidence (3 references)

PMID:20716751 SUPPORT Human Clinical

"This study suggests that both clinical presentations can be caused by mutations in desmosomal protein genes."

Establishes that a dilated, poorly contracting left ventricle and right-dominant arrhythmogenic disease are alternative presentations of the same desmosomal lesion, which is the premise of this entry.

PMID:33949662 SUPPORT Human Clinical

"Our findings confirm the presence of a desmoglein-2-deficient cardiomyopathy among clinically diagnosed dilated cardiomyopathies."

Confirms that DSG2 deficiency is found among patients carrying a clinical diagnosis of dilated cardiomyopathy.

PMID:31078652 SUPPORT Other

"The ACM phenotype overlaps with other cardiomyopathies, particularly dilated cardiomyopathy with arrhythmia presentation that may be associated with ventricular dilatation and/or impaired systolic function."

The governing consensus document states the ACM-to-dilated-cardiomyopathy overlap in exactly the terms this entry is scoped to - ventricular dilatation with impaired systolic function in a patient who would otherwise be classified as arrhythmogenic. Graded OTHER because it is expert consensus rather than a primary study.

Reduced left ventricular ejection fraction Cardiac HP:0012664

Show evidence (1 reference)

PMID:40123482 SUPPORT Human Clinical

"Compared with single-variant carriers, those with multiple variants were more likely to be diagnosed with ARVC (96.2% versus 64.8%; P<0.001) and exhibited more severe left ventricular dysfunction (44.4% versus 22.1%; P=0.001)"

Quantifies left ventricular dysfunction and its dependence on variant burden.

Right ventricular dilatation Cardiac HP:0005133

Show evidence (1 reference)

PMID:41662985 SUPPORT Human Clinical

"Most subjects (74.7%) showed right ventricular dilatation, and nearly half (49.5%) had biventricular involvement."

Gives the frequency of right ventricular dilatation in a genotype-defined DSG2 cohort.

Ventricular tachycardia Cardiac HP:0004756

Sequelae: Sudden cardiac death

Show evidence (2 references)

PMID:41067474 SUPPORT Human Clinical

"Life-threatening ventricular arrhythmias (LTVAs) were the most common clinical presentation (25.8%)."

Establishes ventricular arrhythmia as the commonest presenting feature.

PMID:41067474 SUPPORT Human Clinical

"Non-sustained ventricular tachycardia on Holter monitoring was the only independent predictor of MACE."

Supports the prognostic role of non-sustained ventricular tachycardia stated in this phenotype's description.

Sudden cardiac death Cardiac HP:0001645

Show evidence (1 reference)

PMID:40123482 SUPPORT Human Clinical

"Of the 200 cases with diagnosed ARVC, 41 (20.5%) experienced premature cardiac death before the age of 65."

Quantifies premature cardiac death in a DSG2/DSC2-defined cohort.

Congestive heart failure Cardiac HP:0001635

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:41067474 SUPPORT Human Clinical

"After a median follow-up of 92.8 months, 35.3% of patients experienced LTVAs, and 10.9% developed HF."

Gives the incidence of heart failure over long follow-up in DSG2 disease.

T-wave inversion Cardiac HP:0010872

Show evidence (1 reference)

PMID:41662985 SUPPORT Human Clinical

"Compared with single heterozygous variant carriers, compound and homozygous variant carriers had a younger age at onset, more T-wave inversion, epsilon waves, and biventricular involvement (all pairwise P < .05)."

Reports T-wave inversion and its dependence on allele dose.

Myocardial fibrosis Cardiac HP:0001685

Show evidence (2 references)

PMID:26085008 SUPPORT Model Organism

Names both fibrosis patterns - interstitial and focal replacement - and reports that every animal in the cardiomyocyte-specific Dsg2 knockout developed them alongside chamber dilation.

PMID:28764973 SUPPORT Human Clinical

"Endocardial and transmural fibrosis was increased in all pediatric DCM patients compared to age-matched controls."

Human tissue evidence of fibrosis in dilated cardiomyopathy with reduced desmoglein-2 signal.

🧬

Genetic Associations

DSG2 Loss-of-Function and Missense Variants (Causative)

Gene: DSG2 hgnc:3049

Autosomal dominant Autosomal recessive

Show evidence (5 references)

PMID:16773573 SUPPORT Human Clinical

"We identified four probands with ARVD/C caused by mutations in DSG2, which encodes desmoglein-2, a component of the cardiac desmosome."

The original report establishing DSG2 as a disease gene for desmosomal cardiomyopathy.

PMID:40123482 SUPPORT Human Clinical

"A total of 181 (66.8%) individuals carried missense variants, mainly distributed in the extracellular domains."

Establishes the missense predominance and the extracellular-domain clustering described in this genetic block.

PMID:23381804 SUPPORT In Vitro

"The results suggested a dominant-negative effect of the mutated DSG2 proteins because they were incorporated into the desmosomes."

Directly supports the dominant-negative mechanism asserted for missense alleles, and gives the reason - mutant protein reaches the junction rather than being degraded.

+ 2 more references

💊

Medical Actions

Implantable cardioverter-defibrillator

Action: implantable cardioverter-defibrillator placement Ontology label: Implantable Cardioverter-Defibrillator Placement NCIT:C80435

Platform: Device

Device therapy for prevention of sudden arrhythmic death. Because life-threatening ventricular arrhythmia is the commonest presentation of DSG2 disease and may precede significant structural change, ICD decisions are made on arrhythmic risk rather than on ejection fraction alone.

Mechanism Target:

Ventricular tachycardia — Terminates sustained ventricular tachyarrhythmia before it degenerates.

Show evidence (2 references)

PMID:41652012 SUPPORT Human Clinical

"The strong correlation between predicted and observed arrhythmic outcomes over a five-year horizon validates its application in guiding clinical decisions, ICD implantation strategies, and broader preventive interventions in DSG2 variant carriers."

Supports the specific claim this treatment makes - that in DSG2 carriers the device decision is driven by predicted arrhythmic risk. The prediction tool's agreement with observed events in a genotype-defined cohort is what licenses risk-based rather than ejection-fraction-based ICD selection.

PMID:34263121 SUPPORT INDIRECT Human Clinical

"She subsequently underwent implantation of a cardiac defibrillator for primary prevention given her significantly reduced LVEF despite guideline-directed medical therapy, ongoing heart failure symptoms, and an expected meaningful survival of more than 1 year."

A worked primary-prevention implantation in a DSG2 carrier with the dilated, left-dominant phenotype this entry curates. Graded INDIRECT because a single case documents the indication being applied rather than the device's effect on mortality.

Exercise restriction

Action: avoid excessive exercise Ontology label: Lifestyle Therapy NCIT:C15900

Platform: Behavioral / lifestyle

Avoidance of endurance and competitive high-intensity exercise. This is the only intervention with human evidence of modifying penetrance and arrhythmic risk in desmosomal mutation carriers, and applies to clinically unaffected carriers as well as to affected patients.

Mechanism Target:

Mechanical Uncoupling of Cardiomyocytes — Reducing wall stress reduces the mechanical load on an already compromised intercalated disc.

Show evidence (1 reference)

PMID:23871885 SUPPORT Human Clinical

"These findings support exercise restriction for these patients."

The study's own therapeutic conclusion, drawn from the observed dose-response between exercise and events.

Heart failure pharmacotherapy

Action: Pharmacotherapy NCIT:C15986

Agent: carvedilol CHEBI:3441 enalapril CHEBI:4784 spironolactone CHEBI:9241 sacubitril (given as the sacubitril/valsartan ARNI) NCIT:C152281 dapagliflozin CHEBI:85078

Platform: Small molecule

Contemporary four-pillar guideline-directed medical therapy for dilated cardiomyopathy with reduced ejection fraction - beta-blockade, angiotensin receptor-neprilysin inhibition (or renin-angiotensin system inhibition where an ARNI is not tolerated), mineralocorticoid receptor antagonism, and an SGLT2 inhibitor. This is disease-modifying for the heart failure arm but is not specific to the desmosomal lesion, and no DSG2-specific trial evidence exists.

Mechanism Target:

Progressive Contractile Dysfunction and Heart Failure — Neurohormonal blockade slows progression of contractile dysfunction in dilated cardiomyopathy generally.

Show evidence (1 reference)

PMID:34263121 SUPPORT INDIRECT Human Clinical

"the patient was diagnosed with left-dominant ACM and was managed according to published recommendations with guideline-directed medical therapy (carvedilol 12.5 mg twice daily and sacubitril–valsartan 49–51 mg twice daily)"

Documents contemporary guideline-directed therapy including an ARNI being given for the dilated, left-dominant DSG2 phenotype this entry curates. Graded INDIRECT because a single treated case establishes that the regimen is applied here, not that it changes outcome in this genotype.

Antiarrhythmic pharmacotherapy

Action: Pharmacotherapy NCIT:C15986

Agent: sotalol CHEBI:63622 amiodarone CHEBI:2663

Platform: Small molecule

Antiarrhythmic drug therapy, most often a beta-blocker with or without sotalol or amiodarone, used to reduce arrhythmia burden and appropriate ICD therapies. Adjunctive to, not a substitute for, device therapy in patients at risk of sudden death.

Mechanism Target:

Ventricular tachycardia — Suppression of ventricular ectopy and sustained tachyarrhythmia.

Cardiac transplantation

Action: heart transplantation Ontology label: Organ Transplantation NCIT:C15289

Platform: Surgery

Definitive therapy for end-stage disease. Relevant to this entry more than to the right-dominant arrhythmogenic entries because DSG2 and DSC2 carriers reach end-stage heart failure significantly more often than PKP2 carriers do.

Mechanism Target:

Progressive Contractile Dysfunction and Heart Failure — Replaces the failing organ once medical therapy is exhausted.

Show evidence (1 reference)

PMID:40123482 SUPPORT INDIRECT Human Clinical

"Compared with PKP2 patients, DSG2/DSC2 patients exhibited a significantly higher risk of end-stage heart failure (P<0.001)."

Supports the claim that transplantation is disproportionately relevant in this genotype. Graded INDIRECT because the study reports the heart-failure endpoint rather than transplantation rates directly.

Cascade genetic screening and family evaluation

Action: Genetic Counseling NCIT:C15240

Platform: Other

Predictive DSG2 testing and cardiac evaluation of first-degree relatives. Particularly important here because biallelic families present without an apparent family history - the obligate heterozygous parents are unaffected - so a negative family history does not exclude an inherited cause.

Show evidence (1 reference)

PMID:33917638 SUPPORT Human Clinical

"Therefore, we suggest performing deep genetic analyses using NGS in combination with SNP arrays also for ACM index patients without obvious familial medical history."

Explicit recommendation to pursue genetic analysis despite a negative family history, which is the point of this treatment entry.

🌍

Environmental Factors

Endurance and high-intensity exercise

Exercise is the principal environmental modifier of desmosomal cardiomyopathy. Because the underlying lesion is a failure of mechanical coupling, repeated high wall-stress loading accelerates myocyte detachment and death. Endurance athletes carrying desmosomal mutations become symptomatic younger, meet diagnostic criteria more often, and have worse arrhythmia-free and heart-failure-free survival; reducing exercise lowers subsequent arrhythmic risk. This makes exercise restriction a genuine disease-modifying intervention rather than generic advice.

Show evidence (2 references)

PMID:23871885 SUPPORT Human Clinical

"Endurance exercise and frequent exercise increase the risk of VT/VF, HF, and ARVD/C in desmosomal mutation carriers."

Establishes exercise as a modifier of penetrance and arrhythmic risk in desmosomal mutation carriers, the class this entry belongs to.

PMID:40123482 SUPPORT Human Clinical

"Single-variant carriers who engaged in intense physical exercise were younger at disease onset compared with those who did not (P=0.001)."

DSG2/DSC2-specific evidence that exercise brings disease onset forward, rather than relying only on the mixed-desmosomal-gene cohort above.

Mechanism Target:

EXACERBATES Mechanical Uncoupling of Cardiomyocytes — High-intensity and endurance exercise raise ventricular wall stress and so increase the mechanical load borne by an already weakened intercalated disc, accelerating myocyte detachment.

Show evidence (1 reference)

PMID:23871885 SUPPORT INDIRECT Human Clinical

"Among individuals in the top quartile, a reduction in exercise decreased VT/VF risk (p = 0.04)."

The reversibility of risk on reducing exercise supports mechanical load acting on the disease substrate. Graded INDIRECT because the measured outcome is arrhythmic risk, not the adhesion node itself.

🔬

Diagnosis

Cardiac magnetic resonance imaging with late gadolinium enhancement

The modality that decides this entry. Echocardiography establishes that the ventricle is dilated and hypocontractile but cannot say why; CMR resolves the fibrofatty tissue characterisation - non-ischaemic mid-myocardial and epicardial late gadolinium enhancement, fatty infiltration, regional dyskinesia - that separates a DSG2 desmosomal cardiomyopathy from an otherwise identical idiopathic dilated cardiomyopathy. In the left-dominant presentation this entry curates, CMR is often what converts a working diagnosis of dilated cardiomyopathy into arrhythmogenic cardiomyopathy.

cardiac magnetic resonance imaging with late gadolinium enhancement NCIT:C137915

Late gadolinium enhancement is not currently accepted as a stand-alone diagnostic criterion for left-dominant disease. The same case report that demonstrates CMR making the diagnosis also records that the patient failed the structural criteria of the 2010 modified Task Force criteria because her right ventricle was preserved - see the Task Force criteria entry below.

Show evidence (2 references)

PMID:34263121 SUPPORT Human Clinical

"Subsequent CMR imaging confirmed the diagnosis of left-dominant ACM by demonstrating regional biventricular dyskinesia and a characteristic pattern of fibrofatty myocardial replacement."

In a DSG2 carrier initially classified as dilated cardiomyopathy, CMR was the study that made the diagnosis, which is the claim this entry makes.

PMID:40956261 SUPPORT Human Clinical

"Cardiac magnetic resonance confirmed severe right ventricular dilatation and dysfunction with apical akinesia and diffuse late gadolinium enhancement (LGE) of the RV without signs of a shunt."

Independent human case showing the chamber and late-gadolinium findings CMR contributes in DSG2 disease.

12-lead electrocardiography

Repolarisation and depolarisation abnormalities - precordial T-wave inversion, low QRS voltages, fragmented QRS, epsilon waves - are the cheapest and earliest disease signal, and their burden tracks with allele dose. The ECG is also the screening instrument used in genotype-positive relatives before any structural change is detectable.

12-lead electrocardiography NCIT:C38053

Show evidence (2 references)

PMID:41652012 SUPPORT Human Clinical

"In our Padua cohort, most DSG2 carriers met the revised Task Force criteria (2010TFC), with classical features such as precordial T-wave inversion, RV dilation, and dysfunction"

Establishes precordial T-wave inversion as a classical and frequent ECG finding in a genotype-defined DSG2 cohort.

PMID:40956261 SUPPORT Human Clinical

"The electrocardiogram in sinus rhythm showed large P waves, normal PR interval with peripheral low voltage, a fragmented QRS interval, and T-wave inversions in V1 to V5"

Worked example of the depolarisation and repolarisation abnormalities recorded in a homozygous DSG2 carrier.

Ambulatory Holter electrocardiographic monitoring

Twenty-four-hour and longer ambulatory monitoring quantifies ventricular ectopic burden and captures non-sustained ventricular tachycardia. This is not only a diagnostic test but the single prognostic measurement in this disease - non-sustained ventricular tachycardia on Holter is the only independent predictor of major adverse cardiovascular events in the pooled DSG2 series, so it feeds the device decision directly.

ambulatory Holter electrocardiographic monitoring NCIT:C38064

Show evidence (2 references)

PMID:41067474 SUPPORT Human Clinical

"Non-sustained ventricular tachycardia on Holter monitoring was the only independent predictor of MACE."

Establishes the prognostic yield of ambulatory monitoring in DSG2 disease, which is why it is a required rather than optional part of evaluation.

PMID:34263121 SUPPORT Human Clinical

"Holter monitoring revealed frequent PVCs (>5000 PVCs/24 hours) and sixteen episodes of nonsustained monomorphic ventricular tachycardia (VT) with rates up to 152 bpm"

Worked example of the ectopic burden and non-sustained ventricular tachycardia that ambulatory monitoring detects in a DSG2 carrier.

Transthoracic echocardiography

First-line imaging. It establishes the dilated, hypocontractile phenotype that places a patient in this entry and is the practical surveillance modality for genotype-positive, phenotype-negative relatives identified by cascade testing. It does not characterise tissue, so it cannot by itself distinguish desmosomal from non-desmosomal dilated cardiomyopathy.

transthoracic echocardiography NCIT:C16525

Show evidence (2 references)

PMID:40956261 SUPPORT Human Clinical

"Transthoracic echocardiography already revealed a dilated LV with moderately reduced LVEF of 38% and a dilated RV with reduced function, apical right ventricular akinesia, and moderate tricuspid regurgitation."

Shows echocardiography establishing the biventricular dilated phenotype in a homozygous DSG2 carrier.

PMID:41652012 SUPPORT Human Clinical

"ECG, echocardiography, and cardiac magnetic resonance (CMR) evaluations were performed according to the current ESC 2023 Guidelines"

Records the standard evaluation triad applied to a DSG2-positive cohort, of which echocardiography is the first-line component.

Arrhythmogenic cardiomyopathy next-generation sequencing panel including DSG2

A broad cardiomyopathy and arrhythmogenic-cardiomyopathy NGS panel containing DSG2, with deletion and duplication analysis. Panel breadth and read depth matter more here than in most Mendelian disease: a hemizygous genotype in which a point mutation is unmasked by a large deletion of the second allele is invisible to sequencing alone, and a low-coverage panel has been shown to miss a DSG2 variant that a later high-coverage panel found. Testing must be coupled to genetic counselling and cascade evaluation.

arrhythmogenic cardiomyopathy next-generation sequencing gene panel NCIT:C15709

Show evidence (4 references)

PMID:40956261 SUPPORT Human Clinical

"Therefore, repeat genetic testing including a large panel with high coverage is crucial to establish the correct diagnosis, as was done in this case."

Documents a false-negative first genetic test in a homozygous DSG2 patient and the panel breadth and coverage that were needed to find the variant.

PMID:41652012 SUPPORT Human Clinical

"These multilocus mechanisms underscore the limitations of conventional single-gene testing and emphasize the need for comprehensive molecular diagnostics, including CNV analysis and broad gene panel screening, particularly in cases presenting with atypical or severe phenotypes."

Supports both the panel-over-single-gene and the copy-number-analysis components of this entry, in a DSG2-specific cohort.

PMID:33917638 SUPPORT Human Clinical

"Therefore, we suggest performing deep genetic analyses using NGS in combination with SNP arrays also for ACM index patients without obvious familial medical history."

States the specific recommendation - sequencing plus a copy-number method, even without a family history - that the biallelic subtype of this entry makes necessary.

+ 1 more reference

Task Force and Padua diagnostic criteria

The 2010 modified International Task Force criteria and the 2020 Padua criteria are the formal diagnostic frameworks. The distinction matters specifically for this entry: the Task Force criteria are built around right ventricular structural abnormality and systematically under-recognise the left-dominant presentation, whereas the Padua criteria add left ventricular tissue characterisation and so classify the biventricular and left-dominant forms that CMD1BB describes.

application of the Task Force and Padua diagnostic criteria

Deliberately left without an ontology binding. NCIT has no clinical-action term for applying a named diagnostic criterion set, and this is an assessment framework rather than a test; binding it to a generic laboratory or evaluation term would say something false rather than something imprecise. It is recorded here because which criterion set is used determines whether a patient reaches this entry at all.

Show evidence (2 references)

PMID:34263121 SUPPORT Human Clinical

"Recognizing the limitations of the International Task Force criteria and further additions might be needed to properly diagnose left-dominant ACM."

States the criterion-level gap that makes the dilated, left-dominant DSG2 presentation curated here liable to be classified as idiopathic dilated cardiomyopathy.

PMID:41652012 SUPPORT Human Clinical

"The 2020 Padua Criteria15 were applied to enhance diagnostic specificity, allowing precise phenotypic classification of DSG2-related ACM, particularly in distinguishing right-dominant, left-dominant, and biventricular forms."

Establishes that the Padua criteria are what allow the left-dominant and biventricular DSG2 phenotypes to be separated from the right-dominant one.

18F-FDG PET/CT for myocardial inflammation

Not part of routine evaluation, but decisive in the myocarditis-like presentation. Focal myocardial FDG uptake in a DSG2 carrier can reproduce the imaging picture of cardiac sarcoidosis closely enough to satisfy most of its major criteria, and serial scanning tracks the inflammatory activity of the aseptic inflammation node through treatment and withdrawal.

18F-FDG positron emission tomography with computed tomography NCIT:C103512

Show evidence (1 reference)

PMID:40956261 SUPPORT Human Clinical

"18F-FDG PET/CT imaging can be a useful tool in identifying inflammatory activity in patients with ACM."

The report's own conclusion on the role of FDG PET/CT in arrhythmogenic cardiomyopathy, drawn from serial scanning in a homozygous DSG2 patient.

Endomyocardial biopsy

Reserved for the case where an infiltrative, granulomatous or inflammatory alternative is actively suspected; it is not required to diagnose genetic dilated cardiomyopathy. Its value here is exclusionary - the absence of granulomas in a DSG2 carrier with florid myocardial FDG uptake is what argues against cardiac sarcoidosis. Sampling error limits a negative result.

endomyocardial biopsy NCIT:C51674

Show evidence (1 reference)

PMID:40956261 SUPPORT Human Clinical

"Multiple right ventricular and left ventricular endomyocardial biopsies (Supplemental Figure 1) in regions with 18F-FDG uptake on 18F-FDG PET/CT revealed patchy interstitial fibrosis, without granulomas or inflammatory infiltrates."

Biopsy targeted to FDG-avid myocardium in a DSG2 carrier showed fibrosis and no granulomas, which is the exclusionary use this entry describes.

Natriuretic peptide and high-sensitivity troponin measurement

Routine laboratory assessment of the heart failure arm. These are not diagnostic for DSG2 disease and, importantly, do not exclude it: in a homozygous carrier with active myocardial inflammation and recurrent ventricular tachycardia the natriuretic peptide was only mildly raised and serial troponin was not elevated at all.

N-terminal pro-B-type natriuretic peptide measurement NCIT:C96610

Markers: NT-proBNP, high-sensitivity troponin

Both citations are single-patient values, which is the strongest support the fetched sources offer for laboratory testing in this disease. No cohort study of natriuretic peptide or troponin in DSG2 carriers was found, so no threshold, sensitivity, or specificity is asserted here.

Show evidence (2 references)

PMID:40956261 SUPPORT Human Clinical

"There was a mildly elevated N-terminal pro–B-type natriuretic peptide (600 ng/L) and normal kidney function."

Records the natriuretic peptide result in an actively inflamed homozygous DSG2 carrier, supporting the claim that it is only mildly abnormal.

PMID:40956261 SUPPORT Human Clinical

"Serial troponin measurement was not significantly elevated (troponin stable at 16 ng/L); electrolytes, inflammatory signs, and thyroid-stimulating hormone were normal."

A normal serial troponin in a patient with ongoing myocardial inflammation is the negative result behind this entry's caution that these markers do not exclude the disease.

📊

Prevalence

Chinese multicenter DSG2 p.Phe531Cys founder variant cohort

Point Prevalence Unknown

Not a population rate. Recorded as the proportion of a genotype-defined cohort showing biventricular involvement, which is the feature that places a DSG2 carrier in this entry rather than in the right-dominant arrhythmogenic parent entry.

Show evidence (1 reference)

PMID:41662985 SUPPORT Human Clinical

"Most subjects (74.7%) showed right ventricular dilatation, and nearly half (49.5%) had biventricular involvement."

Quantifies how frequently DSG2 disease reaches biventricular involvement in a founder-variant cohort.

Pooled international DSG2-associated arrhythmogenic cardiomyopathy series

Point Prevalence Unknown

Proportion of a 202-patient pooled genotype-defined cohort with a biventricular phenotype, and the proportion developing heart failure over a median 92.8 months.

Show evidence (2 references)

PMID:41067474 SUPPORT Human Clinical

"Most of the patients exhibited a right-dominant (38.1%) or biventricular (31.2%) phenotype."

Establishes that a biventricular phenotype accounts for roughly a third of DSG2 disease, which is the population this entry describes.

PMID:41067474 SUPPORT Human Clinical

"After a median follow-up of 92.8 months, 35.3% of patients experienced LTVAs, and 10.9% developed HF."

Gives the heart-failure and arrhythmia event rates over long follow-up.

🧫

Experimental Models

DSG2 p.R119X patient-derived iPSC cardiomyocytes with isogenic correction IPSC_DERIVED_MODEL

Induced pluripotent stem cells from a patient with homozygous DSG2 p.R119X and complete desmoglein-2 deficiency, differentiated to cardiomyocytes, with an isogenic heterozygously corrected line generated by homology-directed repair. Three-dimensional self-organized tissue rings allow direct force measurement.

Publication

PMID:33949662

Pathograph links

Mechanical Uncoupling of Cardiomyocytes recapitulates fidelity: high Human patient-derived tissue reproduces the mechanical failure that is the core of the entry's mechanism, and isogenic correction rescues it.

Limitations: iPSC-derived cardiomyocytes are immature relative to adult myocardium and the tissue rings lack vasculature, immune cells and haemodynamic loading, so the necrosis and fibrofatty-replacement arms of the disease are not modelled.

Readouts

Maximum contractile force of self-organized tissue rings

Direction: DECREASED

Interpretation: Reduced maximum force is the direct mechanical correlate of lost cardiomyocyte coupling.

Show evidence (1 reference)

PMID:33949662 SUPPORT In Vitro

"Micro-force testing of three-dimensional self-organized tissue rings (SOTRs) revealed tissue fragility and a weak maximum force in SOTRs from R119X-iPSC-CMs."

Reports the force measurement in the mutant line.

Contractile force after AAV-mediated DSG2 replacement

Direction: RESTORED

Interpretation: Restoration of force on gene replacement establishes that the mechanical deficit is caused by desmoglein-2 loss rather than by an unrelated feature of the patient line.

Show evidence (1 reference)

PMID:33949662 SUPPORT In Vitro

"Adeno-associated virus-mediated replacement of DSG2 significantly recovered the contraction force in SOTRs generated from R119X-iPSC-CMs."

Rescue experiment supporting causality and the gene-replacement proof of concept.

Show evidence (1 reference)

PMID:33949662 SUPPORT In Vitro

"Recapitulation and correction of the disease phenotype using iPSC-CMs provide evidence to support the development of precision medicine and the proof of concept for gene replacement therapy for this cardiomyopathy."

Establishes the model as informative for this disease mechanism.

🐁

Animal Models

Cardiomyocyte-specific Dsg2 knockout mouse

Conditional cardiac deletion of Dsg2, used because global Dsg2 knockout is embryonic lethal. Animals are born with a functionally normal heart and develop cardiomyopathy postnatally as mechanical demand rises.

Species

Mouse

Genotype

Cardiomyocyte-specific Dsg2 ablation (Dsg2 protein reduced below 3% in heart)

Publication

PMID:26085008

Pathograph links

Intercalated Disc Desmosome Destabilization recapitulates fidelity: high Reproduces the ultrastructural loss of intercalated disc desmosomes that is the central junctional lesion.

Limitations: Complete cardiac ablation models the biallelic null state, not the heterozygous missense genotype that accounts for most human disease, so it overstates severity for the common adult presentation.

Readouts

Desmosome ultrastructure at the intercalated disc

Direction: ABOLISHED

Interpretation: Absence of desmosome-like structures is the defining structural readout of this node.

Show evidence (1 reference)

PMID:26085008 SUPPORT Model Organism

"Electron microscopy revealed absence of desmosome-like structures and regional loss of intercalated disc adhesion."

Reports the electron microscopy finding behind this readout.

Show evidence (1 reference)

PMID:26085008 SUPPORT Model Organism

"Mice carrying 2 mutant DSG2 alleles coding for Dsg2 lacking part of the adhesive EC1-EC2 domains present an indistinguishable phenotype, which is similar to that observed in human AC patients."

Supports treating this model as informative for human DSG2 disease.

Biventricular Remodeling and Chamber Dilation recapitulates fidelity: moderate Develops pronounced chamber dilation with necrosis, inflammation and replacement fibrosis.

Limitations: Calcifying necrosis is prominent in the mouse and is not a typical feature of human DSG2 cardiomyopathy, so the injury phenotype is not identical.

Readouts

Ventricular chamber dimensions

Direction: INCREASED

Interpretation: Chamber dilation is the structural endpoint this node describes.

Show evidence (1 reference)

PMID:26085008 SUPPORT Model Organism

Reports the dilation phenotype together with its histological context.

Tg-NS Dsg2-N271S transgenic mouse

Transgenic overexpression of a human-equivalent missense allele. Unlike the knockout, this models the dominant-negative missense mechanism that accounts for most human disease, and expression-level series allow a dose-response to be established.

Species

Mouse

Genotype

Cardiac overexpression of Dsg2-N271S (mouse equivalent of human DSG2-N266S)

Publication

PMID:19635863

Pathograph links

Cardiomyocyte Necrosis recapitulates fidelity: high Identifies myocyte necrosis as the initiating injury and traces the sequence through inflammation to fibrous replacement.

Limitations: The phenotype is driven by transgenic overexpression rather than expression from the endogenous locus, so absolute protein stoichiometry is supraphysiological and severity is not directly comparable to human heterozygotes.

Readouts

Myocardial necrosis and inflammatory infiltrate

Direction: INCREASED

Interpretation: Histological necrosis with inflammation is the direct correlate of this node.

Show evidence (1 reference)

PMID:19635863 SUPPORT Model Organism

Reports the necrosis-inflammation-fibrosis sequence behind this readout.

Show evidence (1 reference)

PMID:19635863 SUPPORT Model Organism

"Transgenic mice recapitulated the clinical features of ARVC, including sudden death at young age, spontaneous ventricular arrhythmias, cardiac dysfunction, and biventricular dilatation and aneurysms."

Supports treating this model as informative, including for the biventricular phenotype this entry curates.

{ }

Source YAML

click to show

name: Dilated Cardiomyopathy 1BB
creation_date: "2026-09-01T00:00:00Z"
category: Genetic
description: >-
  DSG2-related familial isolated dilated cardiomyopathy (CMD1BB) is the
  dilated, left-dominant or biventricular presentation of desmoglein-2
  deficiency. Desmoglein-2 is the principal desmosomal cadherin of the
  cardiomyocyte intercalated disc, where the desmosome and the adherens
  junction are intermingled as the area composita. Loss of desmoglein-2
  destabilises that junction, mechanically uncouples adjacent cardiomyocytes,
  and permits myocyte necrosis with aseptic inflammation and fibrofatty
  replacement; the surviving ventricle dilates and loses contractile function.
  The entry is scoped to the presentation in which chamber dilation and
  systolic failure dominate the clinical picture rather than isolated
  right ventricular arrhythmogenic disease. Allele dose is the principal
  determinant of severity: heterozygous carriers typically present in
  adulthood with a milder, frequently event-free course, whereas biallelic
  (homozygous, compound heterozygous, or hemizygous) loss of function gives
  early-onset biventricular disease that can reach transplantation.
synonyms:
- CMD1BB
- cardiomyopathy, dilated, 1BB
- cardiomyopathy, dilated, type 1Bb
- dilated cardiomyopathy type 1BB
- DSG2 familial isolated dilated cardiomyopathy
- familial isolated dilated cardiomyopathy caused by mutation in DSG2
- desmoglein-2-deficient cardiomyopathy
disease_term:
  preferred_term: Dilated Cardiomyopathy 1BB
  term:
    id: MONDO:0013030
    label: dilated cardiomyopathy 1BB
parents:
- Cardiovascular Disease
- Genetic Disorder
classifications:
  harrisons_chapter:
  - classification_value: CARDIOVASCULAR
  mechanistic_category:
  - classification_value: desmosomopathy
notes: >-
  Relationship to neighbouring dismech entries. This entry is the DSG2
  dilated/left-dominant phenotype and is deliberately distinct from
  Arrhythmogenic_Right_Ventricular_Cardiomyopathy, which is the right-dominant
  arrhythmogenic parent and names DSG2 as one of five desmosomal genes
  alongside PKP2, DSP, DSC2 and JUP. It is also distinct from the two
  gene-specific arrhythmogenic entries, PKP2_Cardiomyopathy and
  DSP_Cardiomyopathy, which curate different desmosomal proteins with
  different phenotypic biases; DSG2/DSC2 carriers carry a significantly higher
  risk of end-stage heart failure than PKP2 carriers, which is the clinical
  reason the DSG2 dilated presentation is worth separating rather than folding
  into the arrhythmogenic parent. Dilated_Cardiomyopathy is the
  non-gene-specific parent phenotype and Dilated_Cardiomyopathy_1A is the
  LMNA-related numbered entry; neither carries desmosomal mechanism. What this
  entry adds that none of those carry is the desmosomal-cadherin route
  specifically into a dilated rather than right-dominant phenotype, together
  with the allele-dose contrast between heterozygous adult-onset and biallelic
  early-onset disease.

  Nosological caveat. The right-dominant, biventricular and left-dominant
  presentations of DSG2 disease are a continuum rather than separate diseases,
  and current literature increasingly uses the umbrella term arrhythmogenic
  cardiomyopathy for all of them. CMD1BB is the OMIM/MONDO label for the
  dilated end of that continuum, and this entry curates it as such; a reader
  interested in the right-dominant end should read
  Arrhythmogenic_Right_Ventricular_Cardiomyopathy alongside it. The
  distinction curated here is phenotypic emphasis, not a claim that two
  mechanistically separate diseases exist.

  Why the two GeneReviews references carry no evidence item. PMID:20301486 and
  PMID:20301310 are listed under references and tagged GeneReviews because they
  are the standard overview chapters for this disease area, but neither is cited
  in an evidence item. Both cache as abstract_only, and what NCBI serves for a
  GeneReviews chapter is the scope statement rather than the chapter body - no
  Clinical Characteristics, Diagnosis, Management or Genetic Counseling text is
  retrievable. The only quotable sentence in either is a statement of what the
  chapter covers, which is not a finding and would be exactly the kind of
  purpose-statement snippet this repository's evidence rules exclude. They are
  kept as bibliography rather than dropped, and should be mined if and when a
  full-text cache becomes available.

  What the diagnosis section does and does not cover. Every entry under
  diagnosis is grounded in a DSG2-specific human source. Three things the
  deep-research report lists are deliberately absent because no fetched source
  supports them with a quotable finding in this disease: exercise testing,
  the complete non-cardiac laboratory panel (thyroid, iron indices, creatine
  kinase), and computed tomography for coronary exclusion. Cardiac
  catheterisation and coronary imaging are used in practice to exclude ischaemic
  cardiomyopathy before this diagnosis is made; that exclusion step is real but
  is a property of the dilated-cardiomyopathy work-up generally rather than of
  DSG2 disease, so it is not curated as a DSG2 diagnostic modality here. The
  laboratory entry that is present is carried by two single-patient values and
  says so.
references:
- reference: PMID:20301486
  title: Dilated Cardiomyopathy Overview.
  tags:
  - GeneReviews
- reference: PMID:20301310
  title: Arrhythmogenic Right Ventricular Cardiomyopathy Overview.
  tags:
  - GeneReviews
inheritance:
- name: Autosomal dominant
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  penetrance: INCOMPLETE
  description: >-
    The majority of DSG2-related disease is transmitted as an autosomal
    dominant trait with reduced, age-related and exercise-modulated
    penetrance. Heterozygous carriers of the Chinese p.Phe531Cys founder
    variant remained free of end-stage heart failure and composite events over
    follow-up, which is the clearest available statement of how mild the
    monoallelic course can be.
  evidence:
  - reference: PMID:16773573
    reference_title: DSG2 mutations contribute to arrhythmogenic right ventricular dysplasia/cardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      It is inherited as an autosomal dominant disease with reduced penetrance,
      although autosomal recessive forms of the disease also occur.
    explanation: >-
      States the dominant-with-reduced-penetrance mode and simultaneously
      records that recessive forms exist, which is the contrast this entry
      curates in the second Inheritance block.
  - reference: PMID:41662985
    reference_title: "Clinical features and outcome of arrhythmogenic cardiomyopathy because of a desmoglein-2 founder variant: A multicenter study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Compound and homozygous variant carriers exhibited significantly higher
      incidences of end-stage heart failure and composite events, whereas single
      heterozygous variant carriers remained event-free (all P < .05).
    explanation: >-
      Quantifies the mildness of the monoallelic course in a 91-subject founder
      variant cohort, supporting incomplete penetrance in heterozygotes.
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    A minority of cases are recessive. Biallelic loss of function - homozygous,
    compound heterozygous, or hemizygous where a point mutation is unmasked by
    a large deletion of the second allele - produces earlier-onset,
    biventricular disease, and the obligate heterozygous parents are typically
    unaffected, which is why these families present without an apparent
    family history.
  evidence:
  - reference: PMID:33917638
    reference_title: Hemi- and Homozygous Loss-of-Function Mutations in DSG2 (Desmoglein-2) Cause Recessive Arrhythmogenic Cardiomyopathy with an Early Onset.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In conclusion, a recessive inheritance pattern is likely for both cases,
      which might contribute to the hidden medical history in both families.
    explanation: >-
      Establishes recessive inheritance in two index patients and explains why
      such families lack a family history, which is the diagnostic trap.
genetic:
- name: DSG2 Loss-of-Function and Missense Variants
  gene_term:
    preferred_term: DSG2
    term:
      id: hgnc:3049
      label: DSG2
  association: Causative
  inheritance:
  - name: Autosomal dominant
  - name: Autosomal recessive
  features: >-
    DSG2 encodes desmoglein-2, a type I transmembrane desmosomal cadherin whose
    four extracellular cadherin domains mediate calcium-dependent adhesion to
    desmocollin-2 across the intercalated disc. Pathogenic variants are
    predominantly missense and cluster in the extracellular domains; nonsense,
    frameshift, splice-site and whole-gene deletion alleles also occur and act
    through loss of function. Missense alleles may additionally act in a
    dominant-negative fashion, since mutant protein is incorporated into the
    desmosome rather than degraded. Multiple variants in the same individual
    are common and track with earlier onset and worse outcome.
  evidence:
  - reference: PMID:16773573
    reference_title: DSG2 mutations contribute to arrhythmogenic right ventricular dysplasia/cardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We identified four probands with ARVD/C caused by mutations in DSG2, which
      encodes desmoglein-2, a component of the cardiac desmosome.
    explanation: >-
      The original report establishing DSG2 as a disease gene for desmosomal
      cardiomyopathy.
  - reference: PMID:40123482
    reference_title: Natural History and Clinical Outcomes of Patients With DSG2/DSC2 Variant-Related Arrhythmogenic Right Ventricular Cardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A total of 181 (66.8%) individuals carried missense variants, mainly
      distributed in the extracellular domains.
    explanation: >-
      Establishes the missense predominance and the extracellular-domain
      clustering described in this genetic block.
  - reference: PMID:23381804
    reference_title: Mutated desmoglein-2 proteins are incorporated into desmosomes and exhibit dominant-negative effects in arrhythmogenic right ventricular cardiomyopathy.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      The results suggested a dominant-negative effect of the mutated DSG2
      proteins because they were incorporated into the desmosomes.
    explanation: >-
      Directly supports the dominant-negative mechanism asserted for missense
      alleles, and gives the reason - mutant protein reaches the junction rather
      than being degraded.
  - reference: PMID:23381804
    reference_title: Mutated desmoglein-2 proteins are incorporated into desmosomes and exhibit dominant-negative effects in arrhythmogenic right ventricular cardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These results and further mutation analyses of four additional desmosomal
      genes indicated that ARVC caused by DSG2 mutations is often transmitted by
      recessive or digenic inheritance.
    explanation: >-
      Independent support for the recessive inheritance arm of this entry, from a
      mutation-analysis cohort rather than from the two-family recessive report.
  - reference: PMID:40123482
    reference_title: Natural History and Clinical Outcomes of Patients With DSG2/DSC2 Variant-Related Arrhythmogenic Right Ventricular Cardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Multiple-variant carriers were significantly younger at ARVC diagnosis
      compared with single-variant carriers
    explanation: >-
      Supports the statement that multiple variants track with earlier onset.
  case_fractions:
  - population: Unselected idiopathic dilated cardiomyopathy referral cohort (UK)
    case_fraction_percent: 5.0
    cohort_size: 100
    notes: >-
      Share attributable to all five desmosomal genes screened together
      (plakoglobin, desmoplakin, plakophilin-2, desmoglein-2, desmocollin-2),
      not to DSG2 alone. Recorded here because it is the best available
      denominator for how often a desmosomal lesion underlies an unequivocal
      dilated cardiomyopathy presentation; the DSG2-only fraction is smaller
      and is not separately reported.
    evidence:
    - reference: PMID:20716751
      reference_title: Prevalence of desmosomal protein gene mutations in patients with dilated cardiomyopathy.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Of the 100 patients (mean age at evaluation, 46.8+/-13.8 years; range,
        17.0 to 72.8 years; male sex, 63%), 5 were found to carry pathogenic
        desmosomal protein gene mutations.
      explanation: >-
        Gives the numerator and denominator for the desmosomal share of
        consecutive idiopathic dilated cardiomyopathy referrals.
prevalence:
- population: Chinese multicenter DSG2 p.Phe531Cys founder variant cohort
  measure_type: POINT_PREVALENCE
  prevalence_class: UNKNOWN
  notes: >-
    Not a population rate. Recorded as the proportion of a genotype-defined
    cohort showing biventricular involvement, which is the feature that places
    a DSG2 carrier in this entry rather than in the right-dominant
    arrhythmogenic parent entry.
  evidence:
  - reference: PMID:41662985
    reference_title: "Clinical features and outcome of arrhythmogenic cardiomyopathy because of a desmoglein-2 founder variant: A multicenter study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Most subjects (74.7%) showed right ventricular dilatation, and nearly half
      (49.5%) had biventricular involvement.
    explanation: >-
      Quantifies how frequently DSG2 disease reaches biventricular involvement
      in a founder-variant cohort.
- population: Pooled international DSG2-associated arrhythmogenic cardiomyopathy series
  measure_type: POINT_PREVALENCE
  prevalence_class: UNKNOWN
  notes: >-
    Proportion of a 202-patient pooled genotype-defined cohort with a
    biventricular phenotype, and the proportion developing heart failure over a
    median 92.8 months.
  evidence:
  - reference: PMID:41067474
    reference_title: "Phenotypic spectrum and prognostic stratification in desmoglein-2-associated arrhythmogenic cardiomyopathy: Results from a pooled analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Most of the patients exhibited a right-dominant (38.1%) or biventricular
      (31.2%) phenotype.
    explanation: >-
      Establishes that a biventricular phenotype accounts for roughly a third of
      DSG2 disease, which is the population this entry describes.
  - reference: PMID:41067474
    reference_title: "Phenotypic spectrum and prognostic stratification in desmoglein-2-associated arrhythmogenic cardiomyopathy: Results from a pooled analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      After a median follow-up of 92.8 months, 35.3% of patients experienced
      LTVAs, and 10.9% developed HF.
    explanation: >-
      Gives the heart-failure and arrhythmia event rates over long follow-up.
pathophysiology:
- name: DSG2 Loss of Function at the Cardiac Desmosome
  conforms_to: "desmosomal_adhesion_failure#Desmosomal Component Loss or Blockade"
  description: >-
    Pathogenic DSG2 alleles reduce the amount of functional desmoglein-2
    available to the cardiomyocyte desmosome. Truncating, splice and deletion
    alleles remove the protein outright; extracellular-domain missense alleles
    produce protein that is still incorporated into the junction but cannot
    perform calcium-dependent trans-adhesion to desmocollin-2, so the effect is
    dominant-negative and dose-dependent. This is the initiating molecular
    lesion of the entry.
  role: trigger
  biological_scale: MOLECULAR
  genes:
  - preferred_term: DSG2
    term:
      id: hgnc:3049
      label: DSG2
  cell_types:
  - preferred_term: cardiac muscle cell
    term:
      id: CL:0000746
      label: cardiac muscle cell
  molecular_functions:
  - preferred_term: cadherin binding
    term:
      id: GO:0045296
      label: cadherin binding
    modifier: LOSS_OF_FUNCTION
  cellular_components:
  - preferred_term: desmosome
    term:
      id: GO:0030057
      label: desmosome
  evidence:
  - reference: PMID:33949662
    reference_title: Phenotypic recapitulation and correction of desmoglein-2-deficient cardiomyopathy using human-induced pluripotent stem cell-derived cardiomyocytes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      we identified a homozygous stop-gain mutations in DSG2 (c.C355T, p.R119X)
      that led to complete desmoglein-2 deficiency in a patient with severe
      biventricular heart failure
    explanation: >-
      Directly links a DSG2 null genotype to complete loss of the protein and to
      the biventricular failure phenotype this entry curates.
  - reference: PMID:19635863
    reference_title: Myocyte necrosis underlies progressive myocardial dystrophy in mouse dsg2-related arrhythmogenic right ventricular cardiomyopathy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Investigation of transgenic lines with different levels of transgene
      expression attested to a dose-dependent dominant-negative effect of the
      mutation.
    explanation: >-
      Supports the dominant-negative, dose-dependent character of missense DSG2
      alleles asserted in this node.
  downstream:
  - target: Intercalated Disc Desmosome Destabilization
    causal_link_type: DIRECT
    description: >-
      Absent or non-adhesive desmoglein-2 leaves the intercalated disc unable to
      assemble structurally normal desmosomes.
    evidence:
    - reference: PMID:33949662
      reference_title: Phenotypic recapitulation and correction of desmoglein-2-deficient cardiomyopathy using human-induced pluripotent stem cell-derived cardiomyocytes.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Histological analysis revealed abnormal deposition of desmosome proteins,
        disrupted intercalated disk structures in the myocardium.
      explanation: >-
        Shows the desmoglein-2-null myocardium has structurally disrupted
        intercalated discs, which is the step from lesion to junctional failure.
  - target: Mutant DSG2 Protein Misfolding in the Endoplasmic Reticulum
    causal_link_type: DIRECT
    description: >-
      A branch taken only by misfolding missense alleles. The mutant protein is
      retained and recognised in the endoplasmic reticulum rather than reaching
      the junction, so this route is not available to null alleles that produce
      no protein at all.
    evidence:
    - reference: PMID:39227800
      reference_title: Hyperactivation of ATF4/TGF-β1 signaling contributes to the progressive cardiac fibrosis in Arrhythmogenic cardiomyopathy caused by DSG2 Variant.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Mechanistic investigations revealed that the variant DSG2-F536C protein
        underwent misfolding, leading to its recognition by BiP within the
        endoplasmic reticulum, which triggered endoplasmic reticulum stress,
        activated the PERK-ATF4 signaling pathway and increased ATF4 levels in
        cardiomyocytes.
      explanation: >-
        States that the pathogenic allele's protein product misfolds and is
        recognised by BiP in the endoplasmic reticulum, which is this edge from
        the allele to the misfolding node.

- name: Intercalated Disc Desmosome Destabilization
  conforms_to: "desmosomal_adhesion_failure#Failure of Desmosome Assembly and Intermediate Filament Anchorage"
  description: >-
    Desmosomes at the intercalated disc are reduced in number, structurally
    abnormal, or absent, and the intercellular space at the desmosome and
    adherens-junction level widens. Because the cardiac intercalated disc is an
    area composita in which desmosomal and adherens-junction components are
    intermingled, the destabilisation is not confined to the desmosome proper;
    it also perturbs the junctional protein complexes that the sodium channel
    and gap junctions depend on. This node is the branch point of the entry.
  role: amplifier
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: cardiac muscle cell
    term:
      id: CL:0000746
      label: cardiac muscle cell
  biological_processes:
  - preferred_term: desmosome organization
    term:
      id: GO:0002934
      label: desmosome organization
    modifier: DECREASED
  cellular_components:
  - preferred_term: adherens junction
    term:
      id: GO:0005912
      label: adherens junction
  evidence:
  - reference: PMID:26085008
    reference_title: Desmoglein 2-Dependent Arrhythmogenic Cardiomyopathy Is Caused by a Loss of Adhesive Function.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Electron microscopy revealed absence of desmosome-like structures and
      regional loss of intercalated disc adhesion.
    explanation: >-
      Direct ultrastructural demonstration that cardiomyocyte-specific Dsg2 loss
      abolishes desmosomes at the intercalated disc.
  - reference: PMID:22764152
    reference_title: Intercalated disc abnormalities, reduced Na(+) current density, and conduction slowing in desmoglein-2 mutant mice prior to cardiomyopathic changes.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Assessment by electron microscopy established that intercellular space
      widening at the desmosomes/adherens junctions occurred in Tg-NS/L mice
      before the onset of necrosis and fibrosis.
    explanation: >-
      Establishes that junctional widening precedes cell death, so this node is
      genuinely upstream of the necrosis node rather than a consequence of it.
  - reference: PMID:28764973
    reference_title: Disturbed Desmoglein-2 in the intercalated disc of pediatric patients with dilated cardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This suggests that the architecture of desmosomes is already disturbed in
      the early stages of DCM.
    explanation: >-
      Human pediatric dilated cardiomyopathy tissue showing desmosomal
      architecture is disturbed early, supporting this node's placement upstream
      in a dilated rather than purely arrhythmogenic phenotype.
  downstream:
  - target: Mechanical Uncoupling of Cardiomyocytes
    causal_link_type: DIRECT
    description: >-
      Loss of the load-bearing junction removes mechanical continuity between
      adjacent cardiomyocytes.
    evidence:
    - reference: PMID:26085008
      reference_title: Desmoglein 2-Dependent Arrhythmogenic Cardiomyopathy Is Caused by a Loss of Adhesive Function.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        We propose that loss of Dsg2 compromises adhesion, and that this is a
        major pathogenic mechanism in DSG2-related and probably other
        desmosome-related ACs.
      explanation: >-
        States the adhesion-loss step as the major pathogenic mechanism, which is
        exactly this edge.
  - target: Sodium Current Reduction and Conduction Slowing
    causal_link_type: DIRECT
    description: >-
      Junctional destabilisation perturbs the Nav1.5 sodium channel complex that
      is co-located at the intercalated disc, independently of and earlier than
      any structural myocardial damage.
    evidence:
    - reference: PMID:22764152
      reference_title: Intercalated disc abnormalities, reduced Na(+) current density, and conduction slowing in desmoglein-2 mutant mice prior to cardiomyopathic changes.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Furthermore, co-immunoprecipitation demonstrated an in vivo interaction
        between Dsg2 and the Na(+) channel protein Na(V)1.5.
      explanation: >-
        Provides the molecular basis for the junction-to-sodium-current edge by
        demonstrating a physical Dsg2-NaV1.5 interaction in vivo.
  - target: Plakoglobin Nuclear Redistribution
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Destabilisation of the junctional plaque is the proposed route by which
      plakoglobin becomes available to the nucleus. This edge is the contested
      arm of the entry - see the discussions block.
  - target: Cardiomyocyte NF-kappaB Activation
    causal_link_type: DIRECT
    description: >-
      Desmosomal disruption activates innate immune signalling within the
      cardiomyocyte itself, before and independently of any infiltrating
      inflammatory cell.
  - target: Connexin-43 Gap Junction Remodeling
    causal_link_type: DIRECT
    description: >-
      The mechanical junction and the gap junction share the intercalated disc
      and are interdependent, so loss of desmosomal anchorage is followed by
      mislocalisation and loss of connexin-43 from the disc.
    evidence:
    - reference: PMID:32376797
      reference_title: Stabilization of desmoglein-2 binding rescues arrhythmia in arrhythmogenic cardiomyopathy.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        Dsg2-LP rescued connexin-43 mislocalization and conduction
        irregularities in response to impaired cardiomyocyte cohesion.
      explanation: >-
        Rescue of connexin-43 localisation by restoring desmoglein-2 binding
        establishes the direction of this edge - the adhesion defect causes the
        gap junction defect, not the reverse.

- name: Mechanical Uncoupling of Cardiomyocytes
  conforms_to: "desmosomal_adhesion_failure#Loss of Desmosomal Intercellular Adhesion"
  description: >-
    Adjacent cardiomyocytes are no longer mechanically coupled and the
    myocardium cannot distribute contractile load across the syncytium.
    Tissue-level force generation falls and the tissue becomes fragile under
    the repeated mechanical demand of contraction, which is why exercise is a
    disease modifier rather than an incidental exposure.
  role: effector
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: cardiac muscle cell
    term:
      id: CL:0000746
      label: cardiac muscle cell
  biological_processes:
  - preferred_term: calcium-dependent cell-cell adhesion
    term:
      id: GO:0016339
      label: calcium-dependent cell-cell adhesion
    modifier: DECREASED
  evidence:
  - reference: PMID:33949662
    reference_title: Phenotypic recapitulation and correction of desmoglein-2-deficient cardiomyopathy using human-induced pluripotent stem cell-derived cardiomyocytes.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Micro-force testing of three-dimensional self-organized tissue rings
      (SOTRs) revealed tissue fragility and a weak maximum force in SOTRs from
      R119X-iPSC-CMs.
    explanation: >-
      Direct mechanical measurement in patient-derived human tissue showing that
      desmoglein-2 loss produces a fragile, weakly contracting tissue.
  downstream:
  - target: Cardiomyocyte Necrosis
    causal_link_type: DIRECT
    description: >-
      Mechanically uncoupled myocytes detach and die under continued
      contractile load.
    evidence:
    - reference: PMID:19635863
      reference_title: Myocyte necrosis underlies progressive myocardial dystrophy in mouse dsg2-related arrhythmogenic right ventricular cardiomyopathy.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        We demonstrate for the first time that myocyte necrosis is the key
        initiator of myocardial injury, triggering progressive myocardial damage,
        including an inflammatory response and massive calcification within the
        myocardium, followed by injury repair with fibrous tissue replacement,
        and myocardial atrophy.
      explanation: >-
        Places myocyte necrosis as the initiating injury downstream of the
        adhesion defect and upstream of inflammation and fibrous replacement.

- name: Sodium Current Reduction and Conduction Slowing
  description: >-
    Sodium current density falls and action potential upstroke velocity is
    reduced, slowing conduction longitudinally and transversally and increasing
    arrhythmia inducibility. Crucially this occurs before necrosis and
    replacement fibrosis, so the arrhythmic substrate is not simply a scar
    phenomenon - it is an early, potentially reversible electrical consequence
    of junctional disruption. This is the mechanistic reason a DSG2 carrier can
    die suddenly with a structurally near-normal heart.
  role: effector
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: ventricular cardiac muscle cell
    term:
      id: CL:2000046
      label: ventricular cardiac muscle cell
  molecular_functions:
  - preferred_term: voltage-gated sodium channel activity
    term:
      id: GO:0005248
      label: voltage-gated sodium channel activity
    modifier: DECREASED
  evidence:
  - reference: PMID:22764152
    reference_title: Intercalated disc abnormalities, reduced Na(+) current density, and conduction slowing in desmoglein-2 mutant mice prior to cardiomyopathic changes.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      A reduced action potential (AP) upstroke velocity due to a lower Na(+)
      current density was also observed at this stage of the disease.
    explanation: >-
      Direct electrophysiological measurement of the reduced sodium current that
      defines this node.
  - reference: PMID:22764152
    reference_title: Intercalated disc abnormalities, reduced Na(+) current density, and conduction slowing in desmoglein-2 mutant mice prior to cardiomyopathic changes.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Intercellular space widening at the level of the intercalated disc
      (desmosomes/adherens junctions) and a concomitant reduction in AP upstroke
      velocity as a consequence of lower Na(+) current density lead to slowed
      conduction and increased arrhythmia susceptibility at disease stages
      preceding the onset of necrosis and replacement fibrosis.
    explanation: >-
      Establishes the pre-structural timing that makes this node an independent
      arrhythmic mechanism rather than a downstream scar effect.
  downstream:
  - target: Ventricular tachycardia
    causal_link_type: DIRECT
    description: >-
      Slowed conduction and increased arrhythmia inducibility give the
      ventricular tachyarrhythmias that dominate clinical presentation.

- name: Connexin-43 Gap Junction Remodeling
  description: >-
    Connexin-43, the principal ventricular gap junction protein, is
    mislocalised and reduced at the intercalated disc once desmosomal anchorage
    fails. This is the electrical-coupling counterpart of the sodium-current
    node: the two together explain why conduction is abnormal in DSG2 disease
    before there is enough scar to account for it. Stabilising desmoglein-2
    binding restores connexin-43 localisation and abolishes the conduction
    irregularity, which is what makes this a consequence of the desmosomal
    lesion rather than an independent finding.
  role: effector
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: ventricular cardiac muscle cell
    term:
      id: CL:2000046
      label: ventricular cardiac muscle cell
  biological_processes:
  - preferred_term: gap junction assembly
    term:
      id: GO:0016264
      label: gap junction assembly
    modifier: DECREASED
  cellular_components:
  - preferred_term: connexin-43 gap junction at the intercalated disc
    term:
      id: GO:0005921
      label: gap junction
  evidence:
  - reference: PMID:32376797
    reference_title: Stabilization of desmoglein-2 binding rescues arrhythmia in arrhythmogenic cardiomyopathy.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Dsg2-LP rescued connexin-43 mislocalization and conduction irregularities
      in response to impaired cardiomyocyte cohesion.
    explanation: >-
      Shows connexin-43 mislocalisation is downstream of impaired
      desmoglein-2-dependent cohesion and is reversible by restoring that
      binding.
  - reference: PMID:26085008
    reference_title: Desmoglein 2-Dependent Arrhythmogenic Cardiomyopathy Is Caused by a Loss of Adhesive Function.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      All animals developed AC during postnatal growth with pronounced chamber
      dilation, calcifying cardiomyocyte necrosis, aseptic inflammation,
      interstitial and focal replacement fibrosis, and conduction defects with
      altered connexin 43 distribution.
    explanation: >-
      In vivo confirmation in the cardiomyocyte-specific Dsg2 knockout that
      altered connexin-43 distribution accompanies the conduction defect.
  - reference: PMID:15851108
    reference_title: Remodeling of myocyte gap junctions in arrhythmogenic right ventricular cardiomyopathy due to a deletion in plakoglobin (Naxos disease).
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Connexin43 expression at intercellular junctions was reduced significantly
      in both right and left ventricles in all patients with Naxos disease.
    explanation: >-
      Human myocardial demonstration that a desmosomal lesion reduces junctional
      connexin-43 in both ventricles. Graded INDIRECT because the lesion studied
      is a plakoglobin deletion, not a DSG2 variant, so it supports the
      desmosomal class and is extrapolated to DSG2 here.
  downstream:
  - target: Ventricular tachycardia
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Reduced gap junctional coupling slows and disperses conduction, which with
      the sodium-current deficit supplies the re-entrant substrate for
      ventricular tachyarrhythmia before structural scar is established.
    evidence:
    - reference: PMID:15851108
      reference_title: Remodeling of myocyte gap junctions in arrhythmogenic right ventricular cardiomyopathy due to a deletion in plakoglobin (Naxos disease).
      supports: SUPPORT
      directness: INDIRECT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Remodeling of gap junctions occurs early in Naxos disease, presumably
        because of abnormal linkage between mechanical junctions and the
        cytoskeleton.
      explanation: >-
        Establishes the early, pre-structural timing that makes gap junction
        remodeling an arrhythmic mechanism in its own right. INDIRECT for the
        same plakoglobin-not-desmoglein reason.

- name: Plakoglobin Nuclear Redistribution
  description: >-
    In the canonical model of desmosomal cardiomyopathy, plaque destabilisation
    releases plakoglobin from the junction and it accumulates in the nucleus.
    This node is retained because it is the first step of the mechanism most
    often invoked for fibrofatty replacement, but the evidence base is
    genuinely contested and the node is curated with its refuting evidence
    attached rather than asserted cleanly.
  role: modifier
  biological_scale: MOLECULAR
  cell_types:
  - preferred_term: cardiac muscle cell
    term:
      id: CL:0000746
      label: cardiac muscle cell
  biological_processes:
  - preferred_term: protein localization to nucleus
    term:
      id: GO:0034504
      label: protein localization to nucleus
    modifier: INCREASED
  evidence:
  - reference: PMID:16823493
    reference_title: Suppression of canonical Wnt/beta-catenin signaling by nuclear plakoglobin recapitulates phenotype of arrhythmogenic right ventricular cardiomyopathy.
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: IN_VITRO
    snippet: >-
      We show suppression of DP expression leads to nuclear localization of the
      desmosomal protein plakoglobin and a 2-fold reduction in canonical
      Wnt/beta-catenin signaling through Tcf/Lef1 transcription factors.
    explanation: >-
      The founding demonstration that losing a desmosomal plaque protein sends
      plakoglobin to the nucleus. Graded INDIRECT because it was obtained by
      suppressing desmoplakin, not desmoglein-2; it supports the mechanism for
      the desmosomal class and is extrapolated to DSG2 here rather than shown
      in it.
  - reference: PMID:26676851
    reference_title: "Loss of plakoglobin immunoreactivity in intercalated discs in arrhythmogenic right ventricular cardiomyopathy: protein mislocalization versus epitope masking."
    supports: REFUTE
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Reduced plakoglobin staining in intercalated discs of heart tissue from
      human ARVC patients and in a murine ARVC model is caused by alterations in
      epitope accessibility and not by protein relocalization.
    explanation: >-
      Directly contradicts the redistribution interpretation of the standard
      immunofluorescence finding, and does so in desmoglein-2 mutant mice
      specifically. Curated as REFUTE so the node carries its own contradiction.
  downstream:
  - target: Canonical Wnt Signaling Suppression
    causal_link_type: DIRECT
    description: >-
      Nuclear plakoglobin competes with beta-catenin for Tcf/Lef transcription
      factors, so the canonical Wnt output falls.
    evidence:
    - reference: PMID:16823493
      reference_title: Suppression of canonical Wnt/beta-catenin signaling by nuclear plakoglobin recapitulates phenotype of arrhythmogenic right ventricular cardiomyopathy.
      supports: SUPPORT
      directness: INDIRECT
      evidence_source: IN_VITRO
      snippet: >-
        We show suppression of DP expression leads to nuclear localization of the
        desmosomal protein plakoglobin and a 2-fold reduction in canonical
        Wnt/beta-catenin signaling through Tcf/Lef1 transcription factors.
      explanation: >-
        Quantifies the fall in Tcf/Lef-dependent signalling that accompanies the
        nuclear plakoglobin, which is exactly this edge. INDIRECT for the same
        desmoplakin-not-desmoglein reason.

- name: Canonical Wnt Signaling Suppression
  description: >-
    Canonical Wnt/beta-catenin output through Tcf/Lef falls, de-repressing an
    adipogenic and fibrogenic transcriptional program in the cardiomyocyte
    lineage. This is the transcriptional route to fibrofatty replacement, and
    it is the arm of the entry whose supporting human observation is disputed
    - see the discussions block.
  role: modifier
  biological_scale: MOLECULAR
  cell_types:
  - preferred_term: cardiac muscle cell
    term:
      id: CL:0000746
      label: cardiac muscle cell
  biological_processes:
  - preferred_term: Wnt signaling pathway
    term:
      id: GO:0016055
      label: Wnt signaling pathway
    modifier: DECREASED
  - preferred_term: fat cell differentiation
    term:
      id: GO:0045444
      label: fat cell differentiation
    modifier: INCREASED
  evidence:
  - reference: PMID:16823493
    reference_title: Suppression of canonical Wnt/beta-catenin signaling by nuclear plakoglobin recapitulates phenotype of arrhythmogenic right ventricular cardiomyopathy.
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: IN_VITRO
    snippet: >-
      The ensuing phenotype is increased expression of adipogenic and fibrogenic
      genes and accumulation of fat droplets.
    explanation: >-
      Connects the Wnt suppression to the adipogenic and fibrogenic program that
      this node asserts. INDIRECT for the same desmoplakin-not-desmoglein reason.
  downstream:
  - target: Fibrofatty Myocardial Replacement
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      De-repression of the adipogenic and fibrogenic program is the proposed
      route to fatty replacement. Marked INDIRECT because the DSG2-specific link
      rests on extrapolation from desmoplakin work.

- name: Cardiomyocyte NF-kappaB Activation
  description: >-
    NF-kappaB signalling is activated in the desmosome-deficient cardiomyocyte
    under basal conditions, without an external immune stimulus. This
    cell-autonomous innate immune response is causal for myocardial injury,
    contractile dysfunction and arrhythmia in the Dsg2 mutant mouse, which is
    what makes inflammation a driver of the disease rather than a reaction to
    it.
  role: amplifier
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: cardiac muscle cell
    term:
      id: CL:0000746
      label: cardiac muscle cell
  biological_processes:
  - preferred_term: positive regulation of canonical NF-kappaB signal transduction
    term:
      id: GO:0043123
      label: positive regulation of canonical NF-kappaB signal transduction
    modifier: INCREASED
  evidence:
  - reference: PMID:38564300
    reference_title: NFĸB signaling drives myocardial injury via CCR2+ macrophages in a preclinical model of arrhythmogenic cardiomyopathy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      We found that NFκB signaling in cardiac myocytes drives myocardial injury,
      contractile dysfunction, and arrhythmias in Dsg2mut/mut mice.
    explanation: >-
      Genetic demonstration in a Dsg2 mutant model that cardiomyocyte NF-kappaB
      signalling is causal for injury, dysfunction and arrhythmia.
  downstream:
  - target: CCR2+ Macrophage Recruitment
    causal_link_type: DIRECT
    description: >-
      Cardiomyocyte NF-kappaB signalling is what mobilises CCR2-expressing
      macrophages into the affected myocardium.
    evidence:
    - reference: PMID:38564300
      reference_title: NFĸB signaling drives myocardial injury via CCR2+ macrophages in a preclinical model of arrhythmogenic cardiomyopathy.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        NFκB signaling in cardiac myocytes mobilizes macrophages expressing C-C
        motif chemokine receptor-2 (CCR2+ cells) to affected areas within the
        heart, where they mediate myocardial injury and arrhythmias.
      explanation: >-
        States the cardiomyocyte-to-macrophage recruitment step that this edge
        asserts.

- name: CCR2+ Macrophage Recruitment
  description: >-
    CCR2-expressing macrophages are mobilised into the affected myocardium,
    where they themselves mediate myocardial injury and arrhythmia. Their
    presence is the reason DSG2 disease can present as an apparent myocarditis
    and be mistaken for an infectious or granulomatous myocardial disease.
  role: amplifier
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: CCR2-expressing macrophage
    term:
      id: CL:0000235
      label: macrophage
  biological_processes:
  - preferred_term: macrophage chemotaxis
    term:
      id: GO:0048246
      label: macrophage chemotaxis
    modifier: INCREASED
  evidence:
  - reference: PMID:38564300
    reference_title: NFĸB signaling drives myocardial injury via CCR2+ macrophages in a preclinical model of arrhythmogenic cardiomyopathy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      NFκB signaling in cardiac myocytes mobilizes macrophages expressing C-C
      motif chemokine receptor-2 (CCR2+ cells) to affected areas within the
      heart, where they mediate myocardial injury and arrhythmias.
    explanation: >-
      Establishes both that the CCR2+ population is recruited and that the
      recruited cells are themselves effectors of injury, which is this node.
  downstream:
  - target: Cardiomyocyte Necrosis
    causal_link_type: DIRECT
    description: >-
      Recruited CCR2+ macrophages mediate the myocardial injury.
  - target: Progressive Contractile Dysfunction and Heart Failure
    causal_link_type: DIRECT
    description: >-
      Inflammation depresses contractility in viable muscle, so contractile
      failure is not solely explained by loss of myocardium.
    evidence:
    - reference: PMID:38564300
      reference_title: NFĸB signaling drives myocardial injury via CCR2+ macrophages in a preclinical model of arrhythmogenic cardiomyopathy.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Contractile dysfunction in Dsg2mut/mut mice is caused both by loss of
        heart muscle and negative inotropic effects of inflammation in viable
        muscle.
      explanation: >-
        Explicitly separates the inflammatory contribution to contractile
        failure from the structural one, which is what this edge asserts.

- name: Mutant DSG2 Protein Misfolding in the Endoplasmic Reticulum
  description: >-
    The first step of a parallel, allele-specific route to fibrosis that does
    not run through adhesion loss. Certain missense DSG2 variants misfold in
    the endoplasmic reticulum and are recognised by the chaperone BiP rather
    than trafficking to the junction. Only alleles that make a protein can take
    this route, so it is unavailable to null alleles.
  role: trigger
  biological_scale: MOLECULAR
  cell_types:
  - preferred_term: cardiac muscle cell
    term:
      id: CL:0000746
      label: cardiac muscle cell
  biological_processes:
  - preferred_term: protein folding
    term:
      id: GO:0006457
      label: protein folding
    modifier: DECREASED
  cellular_components:
  - preferred_term: endoplasmic reticulum
    term:
      id: GO:0005783
      label: endoplasmic reticulum
  evidence:
  - reference: PMID:39227800
    reference_title: Hyperactivation of ATF4/TGF-β1 signaling contributes to the progressive cardiac fibrosis in Arrhythmogenic cardiomyopathy caused by DSG2 Variant.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Mechanistic investigations revealed that the variant DSG2-F536C protein
      underwent misfolding, leading to its recognition by BiP within the
      endoplasmic reticulum, which triggered endoplasmic reticulum stress,
      activated the PERK-ATF4 signaling pathway and increased ATF4 levels in
      cardiomyocytes.
    explanation: >-
      States the misfolding and BiP recognition that define this node, and names
      the ER stress response as its consequence.
  downstream:
  - target: PERK-ATF4 Endoplasmic Reticulum Stress Signaling
    causal_link_type: DIRECT
    description: >-
      BiP engagement by the misfolded cadherin triggers endoplasmic reticulum
      stress and activates the PERK-ATF4 branch of the unfolded protein
      response.
    evidence:
    - reference: PMID:39227800
      reference_title: Hyperactivation of ATF4/TGF-β1 signaling contributes to the progressive cardiac fibrosis in Arrhythmogenic cardiomyopathy caused by DSG2 Variant.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Mechanistic investigations revealed that the variant DSG2-F536C protein
        underwent misfolding, leading to its recognition by BiP within the
        endoplasmic reticulum, which triggered endoplasmic reticulum stress,
        activated the PERK-ATF4 signaling pathway and increased ATF4 levels in
        cardiomyocytes.
      explanation: >-
        The same mechanistic sentence carries this edge, stating that the BiP
        recognition triggered the ER stress response and PERK-ATF4 activation.

- name: PERK-ATF4 Endoplasmic Reticulum Stress Signaling
  description: >-
    Endoplasmic reticulum stress activates the PERK-ATF4 branch of the unfolded
    protein response and ATF4 levels rise in the cardiomyocyte. Pharmacological
    inhibition of PERK-ATF4 attenuates progressive fibrosis and systolic
    dysfunction in the corresponding knock-in mouse, so this node is causal for
    the fibrotic outcome rather than a bystander stress marker.
  role: amplifier
  biological_scale: MOLECULAR
  cell_types:
  - preferred_term: cardiac muscle cell
    term:
      id: CL:0000746
      label: cardiac muscle cell
  biological_processes:
  - preferred_term: response to endoplasmic reticulum stress
    term:
      id: GO:0034976
      label: response to endoplasmic reticulum stress
    modifier: INCREASED
  - preferred_term: endoplasmic reticulum unfolded protein response
    term:
      id: GO:0030968
      label: endoplasmic reticulum unfolded protein response
    modifier: INCREASED
  evidence:
  - reference: PMID:39227800
    reference_title: Hyperactivation of ATF4/TGF-β1 signaling contributes to the progressive cardiac fibrosis in Arrhythmogenic cardiomyopathy caused by DSG2 Variant.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Notably, inhibition of the PERK-ATF4 signaling attenuated progressive
      cardiac fibrosis and cardiac systolic dysfunction in Dsg2F536C/F536C
      mice.
    explanation: >-
      Interventional evidence that this node is causally responsible for a share
      of the fibrosis and systolic dysfunction, not merely correlated with it.
  downstream:
  - target: Cardiomyocyte TGF-beta1 Production
    causal_link_type: DIRECT
    description: >-
      Raised ATF4 drives transcription of TGF-beta1 in the cardiomyocyte.
    evidence:
    - reference: PMID:39227800
      reference_title: Hyperactivation of ATF4/TGF-β1 signaling contributes to the progressive cardiac fibrosis in Arrhythmogenic cardiomyopathy caused by DSG2 Variant.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Inhibition of the PERK-ATF4 signaling attenuated the elevated TGF-β1
        levels, ameliorated the progressive cardiac fibrosis and dysfunction in
        Dsg2F536C/F536C mice.
      explanation: >-
        Blocking PERK-ATF4 lowers TGF-beta1, which places TGF-beta1 production
        downstream of this node rather than beside it.

- name: Cardiomyocyte TGF-beta1 Production
  description: >-
    The stressed cardiomyocyte secretes TGF-beta1, which activates neighbouring
    cardiac fibroblasts by paracrine signalling. This is what makes fibrosis a
    direct consequence of the mutant protein's folding behaviour rather than
    only a repair response to myocyte death.
  role: effector
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: cardiac muscle cell
    term:
      id: CL:0000746
      label: cardiac muscle cell
  biological_processes:
  - preferred_term: transforming growth factor beta production
    term:
      id: GO:0071604
      label: transforming growth factor beta production
    modifier: INCREASED
  evidence:
  - reference: PMID:39227800
    reference_title: Hyperactivation of ATF4/TGF-β1 signaling contributes to the progressive cardiac fibrosis in Arrhythmogenic cardiomyopathy caused by DSG2 Variant.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Increased ATF4 facilitated the expression of TGF-β1 in cardiomyocytes,
      thereby activating cardiac fibroblasts through paracrine signaling and
      ultimately promoting cardiac fibrosis in Dsg2F536C/F536C mice.
    explanation: >-
      States that TGF-beta1 is expressed by the cardiomyocyte itself and acts on
      fibroblasts in a paracrine fashion, which is this node.
  downstream:
  - target: Fibrofatty Myocardial Replacement
    causal_link_type: DIRECT
    description: >-
      Cardiomyocyte-derived TGF-beta1 activates cardiac fibroblasts and drives
      the fibrotic component of replacement.
    evidence:
    - reference: PMID:39227800
      reference_title: Hyperactivation of ATF4/TGF-β1 signaling contributes to the progressive cardiac fibrosis in Arrhythmogenic cardiomyopathy caused by DSG2 Variant.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Hyperactivation of the ATF4/TGF-β1 signaling in cardiomyocytes emerges as
        a novel mechanism underlying progressive cardiac fibrosis in ACM.
      explanation: >-
        The study's own conclusion that this axis is a mechanism of progressive
        cardiac fibrosis, which is exactly this edge.

- name: Cardiomyocyte Necrosis
  conforms_to: "desmosomal_adhesion_failure#Acantholysis and Mechanical Failure of Desmosome-Dependent Tissues"
  description: >-
    Detached cardiomyocytes die by necrosis, with myocardial calcification in
    the DSG2 mouse. Necrosis - not apoptosis - is the initiating injury in this
    disease, and it is the event that both provokes the sterile inflammatory
    response and creates the defect that fibrofatty tissue fills.
  role: effector
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: cardiac muscle cell
    term:
      id: CL:0000746
      label: cardiac muscle cell
  biological_processes:
  - preferred_term: cardiomyocyte necrosis
    term:
      id: GO:0008219
      label: cell death
    modifier: INCREASED
  notes: >-
    Deliberately bound to the broad GO term cell death rather than to a
    necrosis-specific one. GO:0070265 necrotic cell death is obsolete;
    GO:0097300 programmed necrotic cell death would assert a regulated
    necroptosis-like mechanism that the DSG2 literature does not establish; and
    GO:0010659 cardiac muscle cell apoptotic process - the binding used on the
    predecessor of this node and widely across the cardiac entries in this KB -
    names apoptosis, which is the mode of death the cited work explicitly
    contrasts this one with. The specificity that is lost sits in
    preferred_term, per the ontology term contract.
  evidence:
  - reference: PMID:19635863
    reference_title: Myocyte necrosis underlies progressive myocardial dystrophy in mouse dsg2-related arrhythmogenic right ventricular cardiomyopathy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      We demonstrate for the first time that myocyte necrosis is the key
      initiator of myocardial injury, triggering progressive myocardial damage,
      including an inflammatory response and massive calcification within the
      myocardium, followed by injury repair with fibrous tissue replacement,
      and myocardial atrophy.
    explanation: >-
      Names necrosis specifically as the initiating injury and places
      inflammation and fibrous replacement downstream of it.
  - reference: PMID:26085008
    reference_title: Desmoglein 2-Dependent Arrhythmogenic Cardiomyopathy Is Caused by a Loss of Adhesive Function.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      All animals developed AC during postnatal growth with pronounced chamber
      dilation, calcifying cardiomyocyte necrosis, aseptic inflammation,
      interstitial and focal replacement fibrosis, and conduction defects with
      altered connexin 43 distribution.
    explanation: >-
      Independent confirmation of calcifying cardiomyocyte necrosis in a
      cardiomyocyte-specific Dsg2 knockout.
  downstream:
  - target: Aseptic Myocardial Inflammation
    causal_link_type: DIRECT
    description: >-
      Necrotic myocytes release damage signals that provoke a sterile
      inflammatory infiltrate.
    evidence:
    - reference: PMID:19635863
      reference_title: Myocyte necrosis underlies progressive myocardial dystrophy in mouse dsg2-related arrhythmogenic right ventricular cardiomyopathy.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        We demonstrate for the first time that myocyte necrosis is the key
        initiator of myocardial injury, triggering progressive myocardial damage,
        including an inflammatory response and massive calcification within the
        myocardium, followed by injury repair with fibrous tissue replacement,
        and myocardial atrophy.
      explanation: >-
        States that the necrosis triggers the inflammatory response, which is
        the direction of this edge.
  - target: Fibrofatty Myocardial Replacement
    causal_link_type: DIRECT
    description: >-
      Necrotic myocardium is repaired by fibrous and adipose tissue rather than
      by myocyte regeneration.
    evidence:
    - reference: PMID:19635863
      reference_title: Myocyte necrosis underlies progressive myocardial dystrophy in mouse dsg2-related arrhythmogenic right ventricular cardiomyopathy.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        followed by injury repair with fibrous tissue replacement, and myocardial
        atrophy
      explanation: >-
        States the necrosis-to-fibrous-replacement sequence that this edge
        asserts.

- name: Aseptic Myocardial Inflammation
  description: >-
    A sterile inflammatory infiltrate occupies the injured myocardium. This is
    the substrate for the myocarditis-like hot phases that DSG2 carriers can
    present with and that are readily misdiagnosed as infectious myocarditis or
    cardiac sarcoidosis - a mimicry severe enough that a homozygous DSG2 case
    met four of five major criteria for isolated cardiac sarcoidosis.
  role: effector
  biological_scale: TISSUE
  cell_types:
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage
  biological_processes:
  - preferred_term: inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
    modifier: INCREASED
  evidence:
  - reference: PMID:26085008
    reference_title: Desmoglein 2-Dependent Arrhythmogenic Cardiomyopathy Is Caused by a Loss of Adhesive Function.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      All animals developed AC during postnatal growth with pronounced chamber
      dilation, calcifying cardiomyocyte necrosis, aseptic inflammation,
      interstitial and focal replacement fibrosis, and conduction defects with
      altered connexin 43 distribution.
    explanation: >-
      Names aseptic inflammation as a feature of the cardiomyocyte-specific Dsg2
      knockout myocardium.
  - reference: PMID:40956261
    reference_title: Inflammatory Features in Homozygous DSG2 Cardiomyopathy Mimicking Cardiac Sarcoidosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Post-transplant histology showed no granulomas, but extensive fibrofatty
      replacement typically seen in ACM.
    explanation: >-
      Human explant histology confirming that the inflammatory presentation which
      mimicked cardiac sarcoidosis was in fact the fibrofatty process of this
      disease, supporting the mimicry claim in this node's description.
  downstream:
  - target: Fibrofatty Myocardial Replacement
    causal_link_type: DIRECT
    description: >-
      The inflammatory phase resolves into fibrous and fatty repair rather than
      restoration of contractile myocardium.
    evidence:
    - reference: PMID:19635863
      reference_title: Myocyte necrosis underlies progressive myocardial dystrophy in mouse dsg2-related arrhythmogenic right ventricular cardiomyopathy.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        followed by injury repair with fibrous tissue replacement, and myocardial
        atrophy
      explanation: >-
        Places the fibrous repair after the inflammatory phase of the injury
        sequence.

- name: Fibrofatty Myocardial Replacement
  description: >-
    Lost myocardium is replaced by fibrous and adipose tissue. In DSG2 disease
    the fatty component has a metabolic contributor as well as a
    transcriptional one: cardiac Dsg2 deletion impairs mTOR-4EBP1-PPAR-alpha
    signalling and hence fatty acid beta-oxidation, so lipid accumulates in the
    myocardium. Fibrogenesis is driven through TGF-beta/Smad3 signalling. The
    resulting tissue is both non-contractile and electrically inhomogeneous.
  role: central_effector
  biological_scale: TISSUE
  cell_types:
  - preferred_term: fibroblast of cardiac tissue
    term:
      id: CL:0002548
      label: fibroblast of cardiac tissue
  - preferred_term: adipocyte
    term:
      id: CL:0000136
      label: adipocyte
  biological_processes:
  - preferred_term: transforming growth factor beta receptor signaling pathway
    term:
      id: GO:0007179
      label: transforming growth factor beta receptor signaling pathway
    modifier: INCREASED
  - preferred_term: extracellular matrix organization
    term:
      id: GO:0030198
      label: extracellular matrix organization
    modifier: INCREASED
  evidence:
  - reference: PMID:40019607
    reference_title: SFRP4 Knockdown Attenuates Dsg2-Deficient Arrhythmogenic Cardiomyopathy by Down-Regulating TGF-β and Smad3.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      SFRP4 knockdown markedly reduced myocardial fibrosis, ventricular
      compliance, and cardiac dilation in Dsg2-/- mice.
    explanation: >-
      Interventional evidence in the Dsg2 knockout that the fibrotic and dilated
      phenotype is driven by an identifiable profibrotic signal rather than being
      passive scarring.
  - reference: PMID:36815030
    reference_title: Reactivation of PPARα alleviates myocardial lipid accumulation and cardiac dysfunction by improving fatty acid β-oxidation in Dsg2-deficient arrhythmogenic cardiomyopathy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      We demonstrated that these phenotypes were caused by decline of fatty acid
      (FA) β-oxidation resulted from impaired mammalian target of rapamycin
      (mTOR) signaling.
    explanation: >-
      Supports the metabolic contribution to myocardial lipid accumulation
      claimed in this node, distinct from the transcriptional adipogenesis route.
  downstream:
  - target: Biventricular Remodeling and Chamber Dilation
    causal_link_type: DIRECT
    description: >-
      Replacement of contractile myocardium by non-contractile tissue drives
      chamber dilation.
    evidence:
    - reference: PMID:19635863
      reference_title: Myocyte necrosis underlies progressive myocardial dystrophy in mouse dsg2-related arrhythmogenic right ventricular cardiomyopathy.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Transgenic mice recapitulated the clinical features of ARVC, including
        sudden death at young age, spontaneous ventricular arrhythmias, cardiac
        dysfunction, and biventricular dilatation and aneurysms.
      explanation: >-
        Links the myocardial damage process to biventricular dilatation, the
        defining structural feature of this entry.
  - target: Ventricular tachycardia
    causal_link_type: DIRECT
    description: >-
      Fibrofatty tissue interposed between surviving myocyte bundles creates the
      re-entrant substrate for scar-related ventricular tachycardia.

- name: Biventricular Remodeling and Chamber Dilation
  conforms_to: "cardiomyopathy_maladaptive_remodeling#Ventricular Remodeling"
  description: >-
    The ventricles dilate. In the presentation this entry curates, the left
    ventricle is involved either dominantly or together with the right, which is
    what distinguishes CMD1BB from the classical right-dominant arrhythmogenic
    picture. Biventricular involvement is the phenotype that predicts heart
    failure progression in DSG2 disease.
  role: central_effector
  biological_scale: TISSUE
  cell_types:
  - preferred_term: ventricular cardiac muscle cell
    term:
      id: CL:2000046
      label: ventricular cardiac muscle cell
  evidence:
  - reference: PMID:41067474
    reference_title: "Phenotypic spectrum and prognostic stratification in desmoglein-2-associated arrhythmogenic cardiomyopathy: Results from a pooled analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Patients with LTVAs had more severe right ventricular dysfunction, whereas
      those developing HF exhibited biventricular involvement.
    explanation: >-
      Establishes that biventricular remodeling, not right-dominant disease, is
      the substrate for heart failure progression - the clinical rationale for
      separating this entry from the right-dominant parent.
  - reference: PMID:40123482
    reference_title: Natural History and Clinical Outcomes of Patients With DSG2/DSC2 Variant-Related Arrhythmogenic Right Ventricular Cardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Among the 81 individuals for whom both left ventricular ejection fraction
      and right ventricular fractional area change data were available at
      presentation, 29 (35.8%) had isolated right ventricular dysfunction, and 16
      (19.8%) had biventricular dysfunction.
    explanation: >-
      Quantifies how often DSG2/DSC2 disease presents with biventricular rather
      than isolated right ventricular dysfunction.
  downstream:
  - target: Progressive Contractile Dysfunction and Heart Failure
    causal_link_type: DIRECT
    description: >-
      A dilated, fibrotically remodeled ventricle progressively loses systolic
      function.

- name: Progressive Contractile Dysfunction and Heart Failure
  conforms_to: "cardiomyopathy_maladaptive_remodeling#Progressive Contractile Dysfunction"
  description: >-
    Systolic function declines and clinical heart failure supervenes. DSG2 and
    DSC2 carriers reach end-stage heart failure significantly more often than
    PKP2 carriers do, which is the principal prognostic difference between this
    entry and PKP2_Cardiomyopathy. Biallelic carriers reach this endpoint
    earlier and more frequently than heterozygotes.
  role: consequence
  biological_scale: ORGANISM
  evidence:
  - reference: PMID:40123482
    reference_title: Natural History and Clinical Outcomes of Patients With DSG2/DSC2 Variant-Related Arrhythmogenic Right Ventricular Cardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Compared with PKP2 patients, DSG2/DSC2 patients exhibited a significantly
      higher risk of end-stage heart failure (P<0.001).
    explanation: >-
      Direct comparative evidence for the prognostic distinction from the PKP2
      entry asserted in this node.
  - reference: PMID:33949662
    reference_title: Phenotypic recapitulation and correction of desmoglein-2-deficient cardiomyopathy using human-induced pluripotent stem cell-derived cardiomyocytes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Our findings confirm the presence of a desmoglein-2-deficient
      cardiomyopathy among clinically diagnosed dilated cardiomyopathies.
    explanation: >-
      The clearest statement in the literature that desmoglein-2 deficiency
      belongs among the dilated cardiomyopathies, which is the identity claim of
      this entry.
  downstream:
  - target: Congestive heart failure
    causal_link_type: DIRECT
    description: >-
      Falling systolic function manifests clinically as congestive heart failure.
phenotypes:
- category: Cardiac
  name: Dilated cardiomyopathy
  description: >-
    Left ventricular or biventricular dilation with impaired systolic function.
    This is the defining phenotype of the entry and what separates it from
    right-dominant arrhythmogenic disease.
  phenotype_term:
    preferred_term: Dilated cardiomyopathy
    term:
      id: HP:0001644
      label: Dilated cardiomyopathy
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:20716751
    reference_title: Prevalence of desmosomal protein gene mutations in patients with dilated cardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This study suggests that both clinical presentations can be caused by
      mutations in desmosomal protein genes.
    explanation: >-
      Establishes that a dilated, poorly contracting left ventricle and
      right-dominant arrhythmogenic disease are alternative presentations of the
      same desmosomal lesion, which is the premise of this entry.
  - reference: PMID:33949662
    reference_title: Phenotypic recapitulation and correction of desmoglein-2-deficient cardiomyopathy using human-induced pluripotent stem cell-derived cardiomyocytes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Our findings confirm the presence of a desmoglein-2-deficient
      cardiomyopathy among clinically diagnosed dilated cardiomyopathies.
    explanation: >-
      Confirms that DSG2 deficiency is found among patients carrying a clinical
      diagnosis of dilated cardiomyopathy.
  - reference: PMID:31078652
    reference_title: "2019 HRS expert consensus statement on evaluation, risk stratification, and management of arrhythmogenic cardiomyopathy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The ACM phenotype overlaps with other cardiomyopathies, particularly
      dilated cardiomyopathy with arrhythmia presentation that may be associated
      with ventricular dilatation and/or impaired systolic function.
    explanation: >-
      The governing consensus document states the ACM-to-dilated-cardiomyopathy
      overlap in exactly the terms this entry is scoped to - ventricular
      dilatation with impaired systolic function in a patient who would
      otherwise be classified as arrhythmogenic. Graded OTHER because it is
      expert consensus rather than a primary study.
  sequelae:
  - target: Congestive heart failure
    description: >-
      Progressive chamber dilation with systolic failure decompensates into
      clinical heart failure.
- category: Cardiac
  name: Reduced left ventricular ejection fraction
  description: >-
    Impaired left ventricular systolic function. In DSG2 disease this may be
    present at diagnosis or develop during follow-up, and is more common and
    more severe in carriers of multiple variants.
  phenotype_term:
    preferred_term: Reduced left ventricular ejection fraction
    term:
      id: HP:0012664
      label: Reduced left ventricular ejection fraction
  evidence:
  - reference: PMID:40123482
    reference_title: Natural History and Clinical Outcomes of Patients With DSG2/DSC2 Variant-Related Arrhythmogenic Right Ventricular Cardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Compared with single-variant carriers, those with multiple variants were
      more likely to be diagnosed with ARVC (96.2% versus 64.8%; P<0.001) and
      exhibited more severe left ventricular dysfunction (44.4% versus 22.1%;
      P=0.001)
    explanation: >-
      Quantifies left ventricular dysfunction and its dependence on variant
      burden.
- category: Cardiac
  name: Right ventricular dilatation
  description: >-
    Right ventricular dilation, present in the large majority of DSG2 carriers
    even where the left ventricle is also involved. Its high frequency is why
    DSG2 disease sits on a continuum with the arrhythmogenic parent entry rather
    than being a purely left-sided disease.
  phenotype_term:
    preferred_term: Right ventricular dilatation
    term:
      id: HP:0005133
      label: Right ventricular dilatation
  evidence:
  - reference: PMID:41662985
    reference_title: "Clinical features and outcome of arrhythmogenic cardiomyopathy because of a desmoglein-2 founder variant: A multicenter study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Most subjects (74.7%) showed right ventricular dilatation, and nearly half
      (49.5%) had biventricular involvement.
    explanation: >-
      Gives the frequency of right ventricular dilatation in a genotype-defined
      DSG2 cohort.
- category: Cardiac
  name: Ventricular tachycardia
  description: >-
    Sustained and non-sustained ventricular tachycardia. Life-threatening
    ventricular arrhythmia is the single most common mode of clinical
    presentation in DSG2 disease, and non-sustained ventricular tachycardia on
    Holter monitoring is an independent predictor of major adverse
    cardiovascular events.
  phenotype_term:
    preferred_term: Ventricular tachycardia
    term:
      id: HP:0004756
      label: Ventricular tachycardia
  evidence:
  - reference: PMID:41067474
    reference_title: "Phenotypic spectrum and prognostic stratification in desmoglein-2-associated arrhythmogenic cardiomyopathy: Results from a pooled analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Life-threatening ventricular arrhythmias (LTVAs) were the most common
      clinical presentation (25.8%).
    explanation: >-
      Establishes ventricular arrhythmia as the commonest presenting feature.
  - reference: PMID:41067474
    reference_title: "Phenotypic spectrum and prognostic stratification in desmoglein-2-associated arrhythmogenic cardiomyopathy: Results from a pooled analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Non-sustained ventricular tachycardia on Holter monitoring was the only
      independent predictor of MACE.
    explanation: >-
      Supports the prognostic role of non-sustained ventricular tachycardia
      stated in this phenotype's description.
  sequelae:
  - target: Sudden cardiac death
    description: >-
      Degeneration of ventricular tachycardia into ventricular fibrillation is
      the mechanism of sudden death in this disease.
- category: Cardiac
  name: Sudden cardiac death
  description: >-
    Sudden arrhythmic death, which may be the first manifestation of disease.
    Premature cardiac death before age 65 occurred in a fifth of diagnosed
    DSG2/DSC2 cases.
  phenotype_term:
    preferred_term: Sudden cardiac death
    term:
      id: HP:0001645
      label: Sudden cardiac death
  evidence:
  - reference: PMID:40123482
    reference_title: Natural History and Clinical Outcomes of Patients With DSG2/DSC2 Variant-Related Arrhythmogenic Right Ventricular Cardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Of the 200 cases with diagnosed ARVC, 41 (20.5%) experienced premature
      cardiac death before the age of 65.
    explanation: >-
      Quantifies premature cardiac death in a DSG2/DSC2-defined cohort.
- category: Cardiac
  name: Congestive heart failure
  description: >-
    Clinical heart failure from progressive biventricular systolic dysfunction.
    It develops in about one in ten DSG2 carriers over long follow-up, and much
    more often in those with biallelic or multiple variants.
  phenotype_term:
    preferred_term: Congestive heart failure
    term:
      id: HP:0001635
      label: Congestive heart failure
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:41067474
    reference_title: "Phenotypic spectrum and prognostic stratification in desmoglein-2-associated arrhythmogenic cardiomyopathy: Results from a pooled analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      After a median follow-up of 92.8 months, 35.3% of patients experienced
      LTVAs, and 10.9% developed HF.
    explanation: >-
      Gives the incidence of heart failure over long follow-up in DSG2 disease.
- category: Cardiac
  name: T-wave inversion
  description: >-
    Repolarisation abnormality on the surface ECG, more frequent in compound
    heterozygous and homozygous carriers than in single heterozygotes, so it is
    part of the allele-dose gradient rather than a uniform feature.
  phenotype_term:
    preferred_term: T-wave inversion
    term:
      id: HP:0010872
      label: T-wave inversion
  evidence:
  - reference: PMID:41662985
    reference_title: "Clinical features and outcome of arrhythmogenic cardiomyopathy because of a desmoglein-2 founder variant: A multicenter study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Compared with single heterozygous variant carriers, compound and homozygous
      variant carriers had a younger age at onset, more T-wave inversion, epsilon
      waves, and biventricular involvement (all pairwise P < .05).
    explanation: >-
      Reports T-wave inversion and its dependence on allele dose.
- category: Cardiac
  name: Myocardial fibrosis
  description: >-
    Interstitial and replacement fibrosis of the ventricular myocardium,
    detectable as late gadolinium enhancement on cardiac magnetic resonance and
    histologically in explanted or biopsied tissue.
  phenotype_term:
    preferred_term: Myocardial fibrosis
    term:
      id: HP:0001685
      label: Myocardial fibrosis
  evidence:
  - reference: PMID:26085008
    reference_title: Desmoglein 2-Dependent Arrhythmogenic Cardiomyopathy Is Caused by a Loss of Adhesive Function.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      All animals developed AC during postnatal growth with pronounced chamber
      dilation, calcifying cardiomyocyte necrosis, aseptic inflammation,
      interstitial and focal replacement fibrosis, and conduction defects with
      altered connexin 43 distribution.
    explanation: >-
      Names both fibrosis patterns - interstitial and focal replacement - and
      reports that every animal in the cardiomyocyte-specific Dsg2 knockout
      developed them alongside chamber dilation.
  - reference: PMID:28764973
    reference_title: Disturbed Desmoglein-2 in the intercalated disc of pediatric patients with dilated cardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Endocardial and transmural fibrosis was increased in all pediatric DCM
      patients compared to age-matched controls.
    explanation: >-
      Human tissue evidence of fibrosis in dilated cardiomyopathy with reduced
      desmoglein-2 signal.
has_subtypes:
- name: Biallelic
  display_name: Biallelic DSG2 loss of function (early onset)
  description: >-
    Homozygous, compound heterozygous, or hemizygous loss of DSG2 function.
    Presents earlier, with more ECG abnormality and more biventricular
    involvement, and progresses to end-stage heart failure and transplantation
    far more often than the monoallelic form. Obligate heterozygous relatives
    are typically unaffected, so these families often present without a family
    history and the disease can be mistaken for sporadic myocarditis.
  evidence:
  - reference: PMID:41662985
    reference_title: "Clinical features and outcome of arrhythmogenic cardiomyopathy because of a desmoglein-2 founder variant: A multicenter study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Homozygous variant carriers experienced significantly earlier MVA than
      compound (P = .013) and single heterozygous variant carriers (P < .001)
    explanation: >-
      Direct evidence for the allele-dose gradient in timing of malignant
      ventricular arrhythmia.
  - reference: PMID:33917638
    reference_title: Hemi- and Homozygous Loss-of-Function Mutations in DSG2 (Desmoglein-2) Cause Recessive Arrhythmogenic Cardiomyopathy with an Early Onset.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Of note, this genetic strategy revealed a homozygous splice site mutation
      (DSG2-c.378+1G>T) in the first patient and a nonsense mutation
      (DSG2-p.L772X) in combination with a large deletion in DSG2 in the second
      one.
    explanation: >-
      Documents both the homozygous and the hemizygous (point mutation unmasked
      by deletion) routes to biallelic loss described in this subtype.
  - reference: PMID:40956261
    reference_title: Inflammatory Features in Homozygous DSG2 Cardiomyopathy Mimicking Cardiac Sarcoidosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Homozygous variants in DSG2, a desmosomal protein, are associated with a
      severe form of biventricular arrhythmogenic cardiomyopathy (ACM).
    explanation: >-
      States the homozygous-to-severe-biventricular association that defines this
      subtype.
- name: Monoallelic
  display_name: Heterozygous DSG2 variant (adult onset)
  description: >-
    A single pathogenic DSG2 allele. Later onset, milder phenotype, and a
    relatively favourable prognosis; in the Chinese founder-variant cohort
    single heterozygotes remained free of end-stage heart failure and composite
    events entirely. Penetrance is incomplete and strongly modified by exercise
    exposure.
  evidence:
  - reference: PMID:41662985
    reference_title: "Clinical features and outcome of arrhythmogenic cardiomyopathy because of a desmoglein-2 founder variant: A multicenter study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Single heterozygous variant carriers held a less severe phenotype and
      relatively favorable prognosis, whereas compound and homozygous variant
      carriers held an advanced phenotype and poorer prognosis.
    explanation: >-
      States the monoallelic-versus-biallelic prognostic contrast that defines
      these two subtypes.
environmental:
- name: Endurance and high-intensity exercise
  description: >-
    Exercise is the principal environmental modifier of desmosomal
    cardiomyopathy. Because the underlying lesion is a failure of mechanical
    coupling, repeated high wall-stress loading accelerates myocyte detachment
    and death. Endurance athletes carrying desmosomal mutations become
    symptomatic younger, meet diagnostic criteria more often, and have worse
    arrhythmia-free and heart-failure-free survival; reducing exercise lowers
    subsequent arrhythmic risk. This makes exercise restriction a genuine
    disease-modifying intervention rather than generic advice.
  evidence:
  - reference: PMID:23871885
    reference_title: Exercise increases age-related penetrance and arrhythmic risk in arrhythmogenic right ventricular dysplasia/cardiomyopathy-associated desmosomal mutation carriers.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Endurance exercise and frequent exercise increase the risk of VT/VF, HF,
      and ARVD/C in desmosomal mutation carriers.
    explanation: >-
      Establishes exercise as a modifier of penetrance and arrhythmic risk in
      desmosomal mutation carriers, the class this entry belongs to.
  - reference: PMID:40123482
    reference_title: Natural History and Clinical Outcomes of Patients With DSG2/DSC2 Variant-Related Arrhythmogenic Right Ventricular Cardiomyopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Single-variant carriers who engaged in intense physical exercise were
      younger at disease onset compared with those who did not (P=0.001).
    explanation: >-
      DSG2/DSC2-specific evidence that exercise brings disease onset forward,
      rather than relying only on the mixed-desmosomal-gene cohort above.
  influences_mechanisms:
  - target: Mechanical Uncoupling of Cardiomyocytes
    environmental_effect: EXACERBATES
    causal_link_type: DIRECT
    description: >-
      High-intensity and endurance exercise raise ventricular wall stress and so
      increase the mechanical load borne by an already weakened intercalated
      disc, accelerating myocyte detachment.
    evidence:
    - reference: PMID:23871885
      reference_title: Exercise increases age-related penetrance and arrhythmic risk in arrhythmogenic right ventricular dysplasia/cardiomyopathy-associated desmosomal mutation carriers.
      supports: SUPPORT
      directness: INDIRECT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Among individuals in the top quartile, a reduction in exercise decreased
        VT/VF risk (p = 0.04).
      explanation: >-
        The reversibility of risk on reducing exercise supports mechanical load
        acting on the disease substrate. Graded INDIRECT because the measured
        outcome is arrhythmic risk, not the adhesion node itself.
diagnosis:
- name: Cardiac magnetic resonance imaging with late gadolinium enhancement
  description: >-
    The modality that decides this entry. Echocardiography establishes that the
    ventricle is dilated and hypocontractile but cannot say why; CMR resolves
    the fibrofatty tissue characterisation - non-ischaemic mid-myocardial and
    epicardial late gadolinium enhancement, fatty infiltration, regional
    dyskinesia - that separates a DSG2 desmosomal cardiomyopathy from an
    otherwise identical idiopathic dilated cardiomyopathy. In the left-dominant
    presentation this entry curates, CMR is often what converts a working
    diagnosis of dilated cardiomyopathy into arrhythmogenic cardiomyopathy.
  diagnosis_term:
    preferred_term: cardiac magnetic resonance imaging with late gadolinium enhancement
    term:
      id: NCIT:C137915
      label: Magnetic Resonance Imaging of the Heart
  evidence:
  - reference: PMID:34263121
    reference_title: "Left-dominant arrhythmogenic cardiomyopathy: an association with desmoglein-2 gene mutation-a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Subsequent CMR imaging confirmed the diagnosis of left-dominant ACM by
      demonstrating regional biventricular dyskinesia and a characteristic
      pattern of fibrofatty myocardial replacement.
    explanation: >-
      In a DSG2 carrier initially classified as dilated cardiomyopathy, CMR was
      the study that made the diagnosis, which is the claim this entry makes.
  - reference: PMID:40956261
    reference_title: Inflammatory Features in Homozygous DSG2 Cardiomyopathy Mimicking Cardiac Sarcoidosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Cardiac magnetic resonance confirmed severe right ventricular dilatation
      and dysfunction with apical akinesia and diffuse late gadolinium
      enhancement (LGE) of the RV without signs of a shunt.
    explanation: >-
      Independent human case showing the chamber and late-gadolinium findings
      CMR contributes in DSG2 disease.
  notes: >-
    Late gadolinium enhancement is not currently accepted as a stand-alone
    diagnostic criterion for left-dominant disease. The same case report that
    demonstrates CMR making the diagnosis also records that the patient failed
    the structural criteria of the 2010 modified Task Force criteria because her
    right ventricle was preserved - see the Task Force criteria entry below.
- name: 12-lead electrocardiography
  description: >-
    Repolarisation and depolarisation abnormalities - precordial T-wave
    inversion, low QRS voltages, fragmented QRS, epsilon waves - are the
    cheapest and earliest disease signal, and their burden tracks with allele
    dose. The ECG is also the screening instrument used in genotype-positive
    relatives before any structural change is detectable.
  diagnosis_term:
    preferred_term: 12-lead electrocardiography
    term:
      id: NCIT:C38053
      label: Electrocardiography
  evidence:
  - reference: PMID:41652012
    reference_title: Integrative genomic and literature assessment of desmoglein 2-related arrhythmogenic cardiomyopathy with Italian cohort validation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In our Padua cohort, most DSG2 carriers met the revised Task Force
      criteria (2010TFC), with classical features such as precordial T-wave
      inversion, RV dilation, and dysfunction
    explanation: >-
      Establishes precordial T-wave inversion as a classical and frequent ECG
      finding in a genotype-defined DSG2 cohort.
  - reference: PMID:40956261
    reference_title: Inflammatory Features in Homozygous DSG2 Cardiomyopathy Mimicking Cardiac Sarcoidosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The electrocardiogram in sinus rhythm showed large P waves, normal PR
      interval with peripheral low voltage, a fragmented QRS interval, and
      T-wave inversions in V1 to V5
    explanation: >-
      Worked example of the depolarisation and repolarisation abnormalities
      recorded in a homozygous DSG2 carrier.
- name: Ambulatory Holter electrocardiographic monitoring
  description: >-
    Twenty-four-hour and longer ambulatory monitoring quantifies ventricular
    ectopic burden and captures non-sustained ventricular tachycardia. This is
    not only a diagnostic test but the single prognostic measurement in this
    disease - non-sustained ventricular tachycardia on Holter is the only
    independent predictor of major adverse cardiovascular events in the pooled
    DSG2 series, so it feeds the device decision directly.
  diagnosis_term:
    preferred_term: ambulatory Holter electrocardiographic monitoring
    term:
      id: NCIT:C38064
      label: Holter Monitoring
  evidence:
  - reference: PMID:41067474
    reference_title: "Phenotypic spectrum and prognostic stratification in desmoglein-2-associated arrhythmogenic cardiomyopathy: Results from a pooled analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Non-sustained ventricular tachycardia on Holter monitoring was the only
      independent predictor of MACE.
    explanation: >-
      Establishes the prognostic yield of ambulatory monitoring in DSG2 disease,
      which is why it is a required rather than optional part of evaluation.
  - reference: PMID:34263121
    reference_title: "Left-dominant arrhythmogenic cardiomyopathy: an association with desmoglein-2 gene mutation-a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Holter monitoring revealed frequent PVCs (>5000 PVCs/24 hours) and sixteen
      episodes of nonsustained monomorphic ventricular tachycardia (VT) with
      rates up to 152 bpm
    explanation: >-
      Worked example of the ectopic burden and non-sustained ventricular
      tachycardia that ambulatory monitoring detects in a DSG2 carrier.
- name: Transthoracic echocardiography
  description: >-
    First-line imaging. It establishes the dilated, hypocontractile phenotype
    that places a patient in this entry and is the practical surveillance
    modality for genotype-positive, phenotype-negative relatives identified by
    cascade testing. It does not characterise tissue, so it cannot by itself
    distinguish desmosomal from non-desmosomal dilated cardiomyopathy.
  diagnosis_term:
    preferred_term: transthoracic echocardiography
    term:
      id: NCIT:C16525
      label: Echocardiography Test
  evidence:
  - reference: PMID:40956261
    reference_title: Inflammatory Features in Homozygous DSG2 Cardiomyopathy Mimicking Cardiac Sarcoidosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Transthoracic echocardiography already revealed a dilated LV with
      moderately reduced LVEF of 38% and a dilated RV with reduced function,
      apical right ventricular akinesia, and moderate tricuspid regurgitation.
    explanation: >-
      Shows echocardiography establishing the biventricular dilated phenotype in
      a homozygous DSG2 carrier.
  - reference: PMID:41652012
    reference_title: Integrative genomic and literature assessment of desmoglein 2-related arrhythmogenic cardiomyopathy with Italian cohort validation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      ECG, echocardiography, and cardiac magnetic resonance (CMR) evaluations
      were performed according to the current ESC 2023 Guidelines
    explanation: >-
      Records the standard evaluation triad applied to a DSG2-positive cohort,
      of which echocardiography is the first-line component.
- name: Arrhythmogenic cardiomyopathy next-generation sequencing panel including DSG2
  description: >-
    A broad cardiomyopathy and arrhythmogenic-cardiomyopathy NGS panel
    containing DSG2, with deletion and duplication analysis. Panel breadth and
    read depth matter more here than in most Mendelian disease: a hemizygous
    genotype in which a point mutation is unmasked by a large deletion of the
    second allele is invisible to sequencing alone, and a low-coverage panel has
    been shown to miss a DSG2 variant that a later high-coverage panel found.
    Testing must be coupled to genetic counselling and cascade evaluation.
  diagnosis_term:
    preferred_term: arrhythmogenic cardiomyopathy next-generation sequencing gene panel
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: PMID:40956261
    reference_title: Inflammatory Features in Homozygous DSG2 Cardiomyopathy Mimicking Cardiac Sarcoidosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Therefore, repeat genetic testing including a large panel with high
      coverage is crucial to establish the correct diagnosis, as was done in
      this case.
    explanation: >-
      Documents a false-negative first genetic test in a homozygous DSG2 patient
      and the panel breadth and coverage that were needed to find the variant.
  - reference: PMID:41652012
    reference_title: Integrative genomic and literature assessment of desmoglein 2-related arrhythmogenic cardiomyopathy with Italian cohort validation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These multilocus mechanisms underscore the limitations of conventional
      single-gene testing and emphasize the need for comprehensive molecular
      diagnostics, including CNV analysis and broad gene panel screening,
      particularly in cases presenting with atypical or severe phenotypes.
    explanation: >-
      Supports both the panel-over-single-gene and the copy-number-analysis
      components of this entry, in a DSG2-specific cohort.
  - reference: PMID:33917638
    reference_title: Hemi- and Homozygous Loss-of-Function Mutations in DSG2 (Desmoglein-2) Cause Recessive Arrhythmogenic Cardiomyopathy with an Early Onset.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Therefore, we suggest performing deep genetic analyses using NGS in
      combination with SNP arrays also for ACM index patients without obvious
      familial medical history.
    explanation: >-
      States the specific recommendation - sequencing plus a copy-number method,
      even without a family history - that the biallelic subtype of this entry
      makes necessary.
  - reference: PMID:34263121
    reference_title: "Left-dominant arrhythmogenic cardiomyopathy: an association with desmoglein-2 gene mutation-a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      she underwent a comprehensive analysis of 67 genes primarily associated
      with inherited forms of arrhythmia and cardiomyopathy
    explanation: >-
      Worked example of the panel size and scope used in practice to reach a
      DSG2 diagnosis in a dilated presentation.
- name: Task Force and Padua diagnostic criteria
  description: >-
    The 2010 modified International Task Force criteria and the 2020 Padua
    criteria are the formal diagnostic frameworks. The distinction matters
    specifically for this entry: the Task Force criteria are built around right
    ventricular structural abnormality and systematically under-recognise the
    left-dominant presentation, whereas the Padua criteria add left ventricular
    tissue characterisation and so classify the biventricular and left-dominant
    forms that CMD1BB describes.
  diagnosis_term:
    preferred_term: application of the Task Force and Padua diagnostic criteria
  evidence:
  - reference: PMID:34263121
    reference_title: "Left-dominant arrhythmogenic cardiomyopathy: an association with desmoglein-2 gene mutation-a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Recognizing the limitations of the International Task Force criteria and
      further additions might be needed to properly diagnose left-dominant ACM.
    explanation: >-
      States the criterion-level gap that makes the dilated, left-dominant DSG2
      presentation curated here liable to be classified as idiopathic dilated
      cardiomyopathy.
  - reference: PMID:41652012
    reference_title: Integrative genomic and literature assessment of desmoglein 2-related arrhythmogenic cardiomyopathy with Italian cohort validation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The 2020 Padua Criteria15 were applied to enhance diagnostic specificity,
      allowing precise phenotypic classification of DSG2-related ACM,
      particularly in distinguishing right-dominant, left-dominant, and
      biventricular forms.
    explanation: >-
      Establishes that the Padua criteria are what allow the left-dominant and
      biventricular DSG2 phenotypes to be separated from the right-dominant one.
  notes: >-
    Deliberately left without an ontology binding. NCIT has no
    clinical-action term for applying a named diagnostic criterion set, and this
    is an assessment framework rather than a test; binding it to a generic
    laboratory or evaluation term would say something false rather than
    something imprecise. It is recorded here because which criterion set is used
    determines whether a patient reaches this entry at all.
- name: 18F-FDG PET/CT for myocardial inflammation
  description: >-
    Not part of routine evaluation, but decisive in the myocarditis-like
    presentation. Focal myocardial FDG uptake in a DSG2 carrier can reproduce
    the imaging picture of cardiac sarcoidosis closely enough to satisfy most
    of its major criteria, and serial scanning tracks the inflammatory activity
    of the aseptic inflammation node through treatment and withdrawal.
  diagnosis_term:
    preferred_term: 18F-FDG positron emission tomography with computed tomography
    term:
      id: NCIT:C103512
      label: Positron Emission Tomography and Computed Tomography Scan
  evidence:
  - reference: PMID:40956261
    reference_title: Inflammatory Features in Homozygous DSG2 Cardiomyopathy Mimicking Cardiac Sarcoidosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      18F-FDG PET/CT imaging can be a useful tool in identifying inflammatory
      activity in patients with ACM.
    explanation: >-
      The report's own conclusion on the role of FDG PET/CT in arrhythmogenic
      cardiomyopathy, drawn from serial scanning in a homozygous DSG2 patient.
- name: Endomyocardial biopsy
  description: >-
    Reserved for the case where an infiltrative, granulomatous or inflammatory
    alternative is actively suspected; it is not required to diagnose genetic
    dilated cardiomyopathy. Its value here is exclusionary - the absence of
    granulomas in a DSG2 carrier with florid myocardial FDG uptake is what
    argues against cardiac sarcoidosis. Sampling error limits a negative result.
  diagnosis_term:
    preferred_term: endomyocardial biopsy
    term:
      id: NCIT:C51674
      label: Endomyocardial Biopsy
  evidence:
  - reference: PMID:40956261
    reference_title: Inflammatory Features in Homozygous DSG2 Cardiomyopathy Mimicking Cardiac Sarcoidosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Multiple right ventricular and left ventricular endomyocardial biopsies
      (Supplemental Figure 1) in regions with 18F-FDG uptake on 18F-FDG PET/CT
      revealed patchy interstitial fibrosis, without granulomas or inflammatory
      infiltrates.
    explanation: >-
      Biopsy targeted to FDG-avid myocardium in a DSG2 carrier showed fibrosis
      and no granulomas, which is the exclusionary use this entry describes.
- name: Natriuretic peptide and high-sensitivity troponin measurement
  description: >-
    Routine laboratory assessment of the heart failure arm. These are not
    diagnostic for DSG2 disease and, importantly, do not exclude it: in a
    homozygous carrier with active myocardial inflammation and recurrent
    ventricular tachycardia the natriuretic peptide was only mildly raised and
    serial troponin was not elevated at all.
  diagnosis_term:
    preferred_term: N-terminal pro-B-type natriuretic peptide measurement
    term:
      id: NCIT:C96610
      label: N-Terminal ProB-type Natriuretic Peptide Measurement
  markers: NT-proBNP, high-sensitivity troponin
  evidence:
  - reference: PMID:40956261
    reference_title: Inflammatory Features in Homozygous DSG2 Cardiomyopathy Mimicking Cardiac Sarcoidosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      There was a mildly elevated N-terminal pro–B-type natriuretic peptide (600
      ng/L) and normal kidney function.
    explanation: >-
      Records the natriuretic peptide result in an actively inflamed homozygous
      DSG2 carrier, supporting the claim that it is only mildly abnormal.
  - reference: PMID:40956261
    reference_title: Inflammatory Features in Homozygous DSG2 Cardiomyopathy Mimicking Cardiac Sarcoidosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Serial troponin measurement was not significantly elevated (troponin
      stable at 16 ng/L); electrolytes, inflammatory signs, and
      thyroid-stimulating hormone were normal.
    explanation: >-
      A normal serial troponin in a patient with ongoing myocardial inflammation
      is the negative result behind this entry's caution that these markers do
      not exclude the disease.
  notes: >-
    Both citations are single-patient values, which is the strongest support the
    fetched sources offer for laboratory testing in this disease. No cohort study
    of natriuretic peptide or troponin in DSG2 carriers was found, so no
    threshold, sensitivity, or specificity is asserted here.
treatments:
- name: Implantable cardioverter-defibrillator
  description: >-
    Device therapy for prevention of sudden arrhythmic death. Because
    life-threatening ventricular arrhythmia is the commonest presentation of
    DSG2 disease and may precede significant structural change, ICD decisions
    are made on arrhythmic risk rather than on ejection fraction alone.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: implantable cardioverter-defibrillator placement
    term:
      id: NCIT:C80435
      label: Implantable Cardioverter-Defibrillator Placement
  target_mechanisms:
  - target: Ventricular tachycardia
    description: >-
      Terminates sustained ventricular tachyarrhythmia before it degenerates.
  evidence:
  - reference: PMID:41652012
    reference_title: Integrative genomic and literature assessment of desmoglein 2-related arrhythmogenic cardiomyopathy with Italian cohort validation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The strong correlation between predicted and observed arrhythmic outcomes
      over a five-year horizon validates its application in guiding clinical
      decisions, ICD implantation strategies, and broader preventive
      interventions in DSG2 variant carriers.
    explanation: >-
      Supports the specific claim this treatment makes - that in DSG2 carriers
      the device decision is driven by predicted arrhythmic risk. The prediction
      tool's agreement with observed events in a genotype-defined cohort is what
      licenses risk-based rather than ejection-fraction-based ICD selection.
  - reference: PMID:34263121
    reference_title: "Left-dominant arrhythmogenic cardiomyopathy: an association with desmoglein-2 gene mutation-a case report."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      She subsequently underwent implantation of a cardiac defibrillator for
      primary prevention given her significantly reduced LVEF despite
      guideline-directed medical therapy, ongoing heart failure symptoms, and an
      expected meaningful survival of more than 1 year.
    explanation: >-
      A worked primary-prevention implantation in a DSG2 carrier with the
      dilated, left-dominant phenotype this entry curates. Graded INDIRECT
      because a single case documents the indication being applied rather than
      the device's effect on mortality.
- name: Exercise restriction
  description: >-
    Avoidance of endurance and competitive high-intensity exercise. This is the
    only intervention with human evidence of modifying penetrance and arrhythmic
    risk in desmosomal mutation carriers, and applies to clinically unaffected
    carriers as well as to affected patients.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: avoid excessive exercise
    term:
      id: NCIT:C15900
      label: Lifestyle Therapy
  target_mechanisms:
  - target: Mechanical Uncoupling of Cardiomyocytes
    description: >-
      Reducing wall stress reduces the mechanical load on an already compromised
      intercalated disc.
  evidence:
  - reference: PMID:23871885
    reference_title: Exercise increases age-related penetrance and arrhythmic risk in arrhythmogenic right ventricular dysplasia/cardiomyopathy-associated desmosomal mutation carriers.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These findings support exercise restriction for these patients.
    explanation: >-
      The study's own therapeutic conclusion, drawn from the observed
      dose-response between exercise and events.
- name: Heart failure pharmacotherapy
  description: >-
    Contemporary four-pillar guideline-directed medical therapy for dilated
    cardiomyopathy with reduced ejection fraction - beta-blockade, angiotensin
    receptor-neprilysin inhibition (or renin-angiotensin system inhibition
    where an ARNI is not tolerated), mineralocorticoid receptor antagonism, and
    an SGLT2 inhibitor. This is disease-modifying for the heart failure arm but
    is not specific to the desmosomal lesion, and no DSG2-specific trial
    evidence exists.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: carvedilol
      term:
        id: CHEBI:3441
        label: carvedilol
    - preferred_term: enalapril
      term:
        id: CHEBI:4784
        label: enalapril
    - preferred_term: spironolactone
      term:
        id: CHEBI:9241
        label: spironolactone
    - preferred_term: sacubitril (given as the sacubitril/valsartan ARNI)
      term:
        id: NCIT:C152281
        label: Sacubitril
    - preferred_term: dapagliflozin
      term:
        id: CHEBI:85078
        label: dapagliflozin
  target_mechanisms:
  - target: Progressive Contractile Dysfunction and Heart Failure
    description: >-
      Neurohormonal blockade slows progression of contractile dysfunction in
      dilated cardiomyopathy generally.
  evidence:
  - reference: PMID:34263121
    reference_title: "Left-dominant arrhythmogenic cardiomyopathy: an association with desmoglein-2 gene mutation-a case report."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the patient was diagnosed with left-dominant ACM and was managed according
      to published recommendations with guideline-directed medical therapy
      (carvedilol 12.5 mg twice daily and sacubitril–valsartan 49–51 mg twice
      daily)
    explanation: >-
      Documents contemporary guideline-directed therapy including an ARNI being
      given for the dilated, left-dominant DSG2 phenotype this entry curates.
      Graded INDIRECT because a single treated case establishes that the regimen
      is applied here, not that it changes outcome in this genotype.
  notes: >-
    Only the beta-blocker and ARNI components carry a DSG2-specific citation,
    and that is a single treated case rather than an outcome study. The
    mineralocorticoid receptor antagonist and SGLT2 inhibitor pillars are listed
    because they are standard care for dilated cardiomyopathy with reduced
    ejection fraction, but no trial has tested any of these agents in
    DSG2-related disease, and citing a general heart failure trial as evidence
    for this entry would overstate what is known. Catheter ablation for
    recurrent ventricular arrhythmia and cardiac resynchronisation therapy for
    standard dyssynchrony indications are likewise part of the management of
    this disease; neither has been added as a treatment entry because the
    abstract-level sources fetched for this entry contain no finding about
    either in DSG2 carriers, only the fact that they are used in arrhythmogenic
    cardiomyopathy generally.
- name: Antiarrhythmic pharmacotherapy
  description: >-
    Antiarrhythmic drug therapy, most often a beta-blocker with or without
    sotalol or amiodarone, used to reduce arrhythmia burden and appropriate ICD
    therapies. Adjunctive to, not a substitute for, device therapy in patients at
    risk of sudden death.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: sotalol
      term:
        id: CHEBI:63622
        label: sotalol
    - preferred_term: amiodarone
      term:
        id: CHEBI:2663
        label: amiodarone
  target_mechanisms:
  - target: Ventricular tachycardia
    description: >-
      Suppression of ventricular ectopy and sustained tachyarrhythmia.
  notes: >-
    No DSG2-specific efficacy data; management follows the arrhythmogenic
    cardiomyopathy consensus rather than genotype-directed evidence.
- name: Cardiac transplantation
  description: >-
    Definitive therapy for end-stage disease. Relevant to this entry more than to
    the right-dominant arrhythmogenic entries because DSG2 and DSC2 carriers
    reach end-stage heart failure significantly more often than PKP2 carriers do.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: heart transplantation
    term:
      id: NCIT:C15289
      label: Organ Transplantation
  target_mechanisms:
  - target: Progressive Contractile Dysfunction and Heart Failure
    description: >-
      Replaces the failing organ once medical therapy is exhausted.
  evidence:
  - reference: PMID:40123482
    reference_title: Natural History and Clinical Outcomes of Patients With DSG2/DSC2 Variant-Related Arrhythmogenic Right Ventricular Cardiomyopathy.
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Compared with PKP2 patients, DSG2/DSC2 patients exhibited a significantly
      higher risk of end-stage heart failure (P<0.001).
    explanation: >-
      Supports the claim that transplantation is disproportionately relevant in
      this genotype. Graded INDIRECT because the study reports the heart-failure
      endpoint rather than transplantation rates directly.
- name: Cascade genetic screening and family evaluation
  description: >-
    Predictive DSG2 testing and cardiac evaluation of first-degree relatives.
    Particularly important here because biallelic families present without an
    apparent family history - the obligate heterozygous parents are unaffected -
    so a negative family history does not exclude an inherited cause.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:33917638
    reference_title: Hemi- and Homozygous Loss-of-Function Mutations in DSG2 (Desmoglein-2) Cause Recessive Arrhythmogenic Cardiomyopathy with an Early Onset.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Therefore, we suggest performing deep genetic analyses using NGS in
      combination with SNP arrays also for ACM index patients without obvious
      familial medical history.
    explanation: >-
      Explicit recommendation to pursue genetic analysis despite a negative
      family history, which is the point of this treatment entry.
experimental_models:
- name: DSG2 p.R119X patient-derived iPSC cardiomyocytes with isogenic correction
  experimental_model_type: IPSC_DERIVED_MODEL
  description: >-
    Induced pluripotent stem cells from a patient with homozygous DSG2 p.R119X
    and complete desmoglein-2 deficiency, differentiated to cardiomyocytes, with
    an isogenic heterozygously corrected line generated by homology-directed
    repair. Three-dimensional self-organized tissue rings allow direct force
    measurement.
  publication: PMID:33949662
  modeled_mechanisms:
  - target: Mechanical Uncoupling of Cardiomyocytes
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Human patient-derived tissue reproduces the mechanical failure that is the
      core of the entry's mechanism, and isogenic correction rescues it.
    limitations: >-
      iPSC-derived cardiomyocytes are immature relative to adult myocardium and
      the tissue rings lack vasculature, immune cells and haemodynamic loading,
      so the necrosis and fibrofatty-replacement arms of the disease are not
      modelled.
    readouts:
    - name: Maximum contractile force of self-organized tissue rings
      target: Mechanical Uncoupling of Cardiomyocytes
      direction: DECREASED
      interpretation: >-
        Reduced maximum force is the direct mechanical correlate of lost
        cardiomyocyte coupling.
      evidence:
      - reference: PMID:33949662
        reference_title: Phenotypic recapitulation and correction of desmoglein-2-deficient cardiomyopathy using human-induced pluripotent stem cell-derived cardiomyocytes.
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: >-
          Micro-force testing of three-dimensional self-organized tissue rings
          (SOTRs) revealed tissue fragility and a weak maximum force in SOTRs
          from R119X-iPSC-CMs.
        explanation: >-
          Reports the force measurement in the mutant line.
    - name: Contractile force after AAV-mediated DSG2 replacement
      target: Mechanical Uncoupling of Cardiomyocytes
      direction: RESTORED
      interpretation: >-
        Restoration of force on gene replacement establishes that the mechanical
        deficit is caused by desmoglein-2 loss rather than by an unrelated
        feature of the patient line.
      evidence:
      - reference: PMID:33949662
        reference_title: Phenotypic recapitulation and correction of desmoglein-2-deficient cardiomyopathy using human-induced pluripotent stem cell-derived cardiomyocytes.
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: >-
          Adeno-associated virus-mediated replacement of DSG2 significantly
          recovered the contraction force in SOTRs generated from R119X-iPSC-CMs.
        explanation: >-
          Rescue experiment supporting causality and the gene-replacement proof
          of concept.
    evidence:
    - reference: PMID:33949662
      reference_title: Phenotypic recapitulation and correction of desmoglein-2-deficient cardiomyopathy using human-induced pluripotent stem cell-derived cardiomyocytes.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        Recapitulation and correction of the disease phenotype using iPSC-CMs
        provide evidence to support the development of precision medicine and the
        proof of concept for gene replacement therapy for this cardiomyopathy.
      explanation: >-
        Establishes the model as informative for this disease mechanism.
animal_models:
- name: Cardiomyocyte-specific Dsg2 knockout mouse
  species: Mouse
  genotype: Cardiomyocyte-specific Dsg2 ablation (Dsg2 protein reduced below 3% in heart)
  publication: PMID:26085008
  description: >-
    Conditional cardiac deletion of Dsg2, used because global Dsg2 knockout is
    embryonic lethal. Animals are born with a functionally normal heart and
    develop cardiomyopathy postnatally as mechanical demand rises.
  modeled_mechanisms:
  - target: Intercalated Disc Desmosome Destabilization
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Reproduces the ultrastructural loss of intercalated disc desmosomes that is
      the central junctional lesion.
    limitations: >-
      Complete cardiac ablation models the biallelic null state, not the
      heterozygous missense genotype that accounts for most human disease, so it
      overstates severity for the common adult presentation.
    readouts:
    - name: Desmosome ultrastructure at the intercalated disc
      target: Intercalated Disc Desmosome Destabilization
      direction: ABOLISHED
      interpretation: >-
        Absence of desmosome-like structures is the defining structural readout
        of this node.
      evidence:
      - reference: PMID:26085008
        reference_title: Desmoglein 2-Dependent Arrhythmogenic Cardiomyopathy Is Caused by a Loss of Adhesive Function.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Electron microscopy revealed absence of desmosome-like structures and
          regional loss of intercalated disc adhesion.
        explanation: >-
          Reports the electron microscopy finding behind this readout.
    evidence:
    - reference: PMID:26085008
      reference_title: Desmoglein 2-Dependent Arrhythmogenic Cardiomyopathy Is Caused by a Loss of Adhesive Function.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Mice carrying 2 mutant DSG2 alleles coding for Dsg2 lacking part of the
        adhesive EC1-EC2 domains present an indistinguishable phenotype, which is
        similar to that observed in human AC patients.
      explanation: >-
        Supports treating this model as informative for human DSG2 disease.
  - target: Biventricular Remodeling and Chamber Dilation
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Develops pronounced chamber dilation with necrosis, inflammation and
      replacement fibrosis.
    limitations: >-
      Calcifying necrosis is prominent in the mouse and is not a typical feature
      of human DSG2 cardiomyopathy, so the injury phenotype is not identical.
    readouts:
    - name: Ventricular chamber dimensions
      target: Biventricular Remodeling and Chamber Dilation
      direction: INCREASED
      interpretation: >-
        Chamber dilation is the structural endpoint this node describes.
      evidence:
      - reference: PMID:26085008
        reference_title: Desmoglein 2-Dependent Arrhythmogenic Cardiomyopathy Is Caused by a Loss of Adhesive Function.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          All animals developed AC during postnatal growth with pronounced
          chamber dilation, calcifying cardiomyocyte necrosis, aseptic
          inflammation, interstitial and focal replacement fibrosis, and
          conduction defects with altered connexin 43 distribution.
        explanation: >-
          Reports the dilation phenotype together with its histological context.
- name: Tg-NS Dsg2-N271S transgenic mouse
  species: Mouse
  genotype: Cardiac overexpression of Dsg2-N271S (mouse equivalent of human DSG2-N266S)
  publication: PMID:19635863
  description: >-
    Transgenic overexpression of a human-equivalent missense allele. Unlike the
    knockout, this models the dominant-negative missense mechanism that accounts
    for most human disease, and expression-level series allow a dose-response to
    be established.
  modeled_mechanisms:
  - target: Cardiomyocyte Necrosis
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Identifies myocyte necrosis as the initiating injury and traces the
      sequence through inflammation to fibrous replacement.
    limitations: >-
      The phenotype is driven by transgenic overexpression rather than expression
      from the endogenous locus, so absolute protein stoichiometry is
      supraphysiological and severity is not directly comparable to human
      heterozygotes.
    readouts:
    - name: Myocardial necrosis and inflammatory infiltrate
      target: Cardiomyocyte Necrosis
      direction: INCREASED
      interpretation: >-
        Histological necrosis with inflammation is the direct correlate of this
        node.
      evidence:
      - reference: PMID:19635863
        reference_title: Myocyte necrosis underlies progressive myocardial dystrophy in mouse dsg2-related arrhythmogenic right ventricular cardiomyopathy.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          We demonstrate for the first time that myocyte necrosis is the key
          initiator of myocardial injury, triggering progressive myocardial
          damage, including an inflammatory response and massive calcification
          within the myocardium, followed by injury repair with fibrous tissue
          replacement, and myocardial atrophy.
        explanation: >-
          Reports the necrosis-inflammation-fibrosis sequence behind this
          readout.
    evidence:
    - reference: PMID:19635863
      reference_title: Myocyte necrosis underlies progressive myocardial dystrophy in mouse dsg2-related arrhythmogenic right ventricular cardiomyopathy.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Transgenic mice recapitulated the clinical features of ARVC, including
        sudden death at young age, spontaneous ventricular arrhythmias, cardiac
        dysfunction, and biventricular dilatation and aneurysms.
      explanation: >-
        Supports treating this model as informative, including for the
        biventricular phenotype this entry curates.
discussions:
- kind: KNOWLEDGE_GAP
  discussion_id: dsg2_plakoglobin_epitope_vs_relocalization
  prompt: >-
    Does plakoglobin actually redistribute to the nucleus in DSG2-related
    cardiomyopathy, or is the reduced junctional plakoglobin signal an artefact
    of epitope masking?
  attaches_to:
  - pathophysiology#Plakoglobin Nuclear Redistribution
  - pathophysiology#Canonical Wnt Signaling Suppression
  rationale: >-
    Reduced junctional plakoglobin immunofluorescence has been proposed as a
    diagnostic marker and as the mechanistic link between desmosomal disruption
    and fibrofatty replacement. That interpretation rests on the signal
    reflecting genuine protein relocalization. Work in desmoglein-2 mutant mice
    and human ARVC biopsies found the reduced signal only with one antibody
    against one epitope and not with three others, concluding that epitope
    accessibility rather than relocalization explains it. If that is right, the
    Wnt-suppression arm of the mechanism loses its principal human observational
    support and the fibrofatty pathway needs a different explanation - for which
    the mTOR-PPAR-alpha metabolic route and TGF-beta/Smad3 fibrogenesis curated
    on the replacement node are the leading candidates. The entry records the
    canonical mechanism and its contradiction side by side rather than choosing.
  proposed_experiments:
  - experiment_id: dsg2_plakoglobin_epitope_independent_quantification
    name: Epitope-independent quantification of plakoglobin compartmentalisation in DSG2 myocardium
    description: >-
      Quantify nuclear versus junctional plakoglobin in DSG2-variant human
      myocardium using a method that does not depend on antibody epitope
      accessibility - for example subcellular fractionation with mass
      spectrometry, or tagged-allele imaging in isogenic iPSC-derived
      cardiomyocytes - alongside a readout of canonical Wnt target gene
      expression.
    would_support:
    - pathophysiology#Plakoglobin Nuclear Redistribution
    - pathophysiology#Canonical Wnt Signaling Suppression
    supporting_outcome:
    - >-
      Nuclear plakoglobin is increased and canonical Wnt target gene expression
      is reduced in DSG2-deficient cardiomyocytes by a method independent of
      antibody epitope accessibility.
    would_refute:
    - pathophysiology#Plakoglobin Nuclear Redistribution
    - pathophysiology#Canonical Wnt Signaling Suppression
    refuting_outcome:
    - >-
      Total and nuclear plakoglobin are unchanged and Wnt target genes are not
      suppressed, indicating the immunofluorescence finding is an epitope
      artefact and the adipogenic program arises by another route.
- kind: KNOWLEDGE_GAP
  discussion_id: dsg2_dilated_vs_right_dominant_boundary
  prompt: >-
    Is the dilated, left-dominant DSG2 presentation curated here a distinct
    entity from right-dominant DSG2 arrhythmogenic cardiomyopathy, or one end of
    a single continuum?
  attaches_to:
  - disease#Dilated Cardiomyopathy 1BB
  - pathophysiology#Biventricular Remodeling and Chamber Dilation
  rationale: >-
    CMD1BB exists as an OMIM and MONDO concept and is curated here on that
    basis, but the genotype-defined cohorts do not separate cleanly: in the
    pooled series 38.1% were right-dominant and 31.2% biventricular, and in the
    founder-variant cohort three quarters had right ventricular dilatation while
    half had biventricular involvement. No mechanism has been identified that
    determines which ventricle dominates in a given DSG2 carrier. Until one is,
    the split between this entry and
    Arrhythmogenic_Right_Ventricular_Cardiomyopathy is a phenotypic and
    nosological convenience rather than a mechanistic boundary, and readers
    should treat it as such.

📚

References & Deep Research

References

PMID:20301486

Dilated Cardiomyopathy Overview.

No top-level findings curated for this source.

PMID:20301310

Arrhythmogenic Right Ventricular Cardiomyopathy Overview.

No top-level findings curated for this source.

Deep Research

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

Evaluations and curation notes (2)

Record notes

Relationship to neighbouring dismech entries. This entry is the DSG2 dilated/left-dominant phenotype and is deliberately distinct from Arrhythmogenic_Right_Ventricular_Cardiomyopathy, which is the right-dominant arrhythmogenic parent and names DSG2 as one of five desmosomal genes alongside PKP2, DSP, DSC2 and JUP. It is also distinct from the two gene-specific arrhythmogenic entries, PKP2_Cardiomyopathy and DSP_Cardiomyopathy, which curate different desmosomal proteins with different phenotypic biases; DSG2/DSC2 carriers carry a significantly higher risk of end-stage heart failure than PKP2 carriers, which is the clinical reason the DSG2 dilated presentation is worth separating rather than folding into the arrhythmogenic parent. Dilated_Cardiomyopathy is the non-gene-specific parent phenotype and Dilated_Cardiomyopathy_1A is the LMNA-related numbered entry; neither carries desmosomal mechanism. What this entry adds that none of those carry is the desmosomal-cadherin route specifically into a dilated rather than right-dominant phenotype, together with the allele-dose contrast between heterozygous adult-onset and biallelic early-onset disease. Nosological caveat. The right-dominant, biventricular and left-dominant presentations of DSG2 disease are a continuum rather than separate diseases, and current literature increasingly uses the umbrella term arrhythmogenic cardiomyopathy for all of them. CMD1BB is the OMIM/MONDO label for the dilated end of that continuum, and this entry curates it as such; a reader interested in the right-dominant end should read Arrhythmogenic_Right_Ventricular_Cardiomyopathy alongside it. The distinction curated here is phenotypic emphasis, not a claim that two mechanistically separate diseases exist. Why the two GeneReviews references carry no evidence item. PMID:20301486 and PMID:20301310 are listed under references and tagged GeneReviews because they are the standard overview chapters for this disease area, but neither is cited in an evidence item. Both cache as abstract_only, and what NCBI serves for a GeneReviews chapter is the scope statement rather than the chapter body - no Clinical Characteristics, Diagnosis, Management or Genetic Counseling text is retrievable. The only quotable sentence in either is a statement of what the chapter covers, which is not a finding and would be exactly the kind of purpose-statement snippet this repository's evidence rules exclude. They are kept as bibliography rather than dropped, and should be mined if and when a full-text cache becomes available. What the diagnosis section does and does not cover. Every entry under diagnosis is grounded in a DSG2-specific human source. Three things the deep-research report lists are deliberately absent because no fetched source supports them with a quotable finding in this disease: exercise testing, the complete non-cardiac laboratory panel (thyroid, iron indices, creatine kinase), and computed tomography for coronary exclusion. Cardiac catheterisation and coronary imaging are used in practice to exclude ischaemic cardiomyopathy before this diagnosis is made; that exclusion step is real but is a property of the dilated-cardiomyopathy work-up generally rather than of DSG2 disease, so it is not curated as a DSG2 diagnostic modality here. The laboratory entry that is present is carried by two single-patient values and says so.

Create: Dilated_Cardiomyopathy_1BB · 2026-09-01T22:41:35Z · View source

Created the DSG2-related dilated cardiomyopathy (CMD1BB, MONDO:0013030) entry from the seeded stub. Deep research: Falcon (Edison Scientific) ran successfully (910s, 31 citations, template_sha 1e7ea4ee); just preflight-dr PASSED against MONDO:0013030 with DSG2 mentioned 75 times and no competing gene, so no Named Entity Confusion. The report's term_validation reported needs_review: true for one obsolete CURIE (GO:0062023, replaced by GO:0031012); that term was not bound in this entry. As is characteristic of Falcon reports in this repo, the report carries ZERO PMIDs -- it cites by author-year key and DOI -- so it was used strictly as leads. Every one of the 73 evidence snippets cites a PMID fetched independently via just fetch-reference from PubMed searches, and all 73 verify as exact substrings of the local reference cache. Falcon did contribute two mechanism arms found nowhere in my own initial PubMed sweep: the cardiomyocyte NF-kappaB / CCR2+ macrophage injury axis (PMID:38564300) and the misfolded-DSG2 ER-stress PERK-ATF4-TGF-beta1 fibrosis route (PMID:39227800); both PMIDs were located by searching PubMed for the DOI-cited titles, then fetched and quoted directly. Pathophysiology is an 11-node connected causal chain from DSG2 loss of function at the desmosome through intercalated-disc destabilization, which branches four ways (mechanical uncoupling, Nav1.5 sodium-current reduction, plakoglobin/Wnt, NF-kappaB inflammation) and reconverges on fibrofatty replacement, biventricular remodeling and heart failure. Three nodes conform to desmosomal_adhesion_failure (which names DSG2 as a route-1 structural gene) and two to cardiomyopathy_maladaptive_remodeling, matching the dual-conformance pattern used by Carvajal_Syndrome. The plakoglobin node is curated WITH its contradiction: PMID:26676851 is recorded as REFUTE because it shows the reduced junctional plakoglobin signal in desmoglein-2 mutant mice is epitope masking rather than relocalization, and a KNOWLEDGE_GAP discussion with a proposed experiment records that dispute rather than resolving it. A second KNOWLEDGE_GAP records that the dilated/right-dominant split between this entry and Arrhythmogenic_Right_Ventricular_Cardiomyopathy is a phenotypic convention, not a demonstrated mechanistic boundary. Allele dose is curated as two has_subtypes (Biallelic, Monoallelic) plus two Inheritance blocks. Two treatments (heart failure pharmacotherapy, antiarrhythmic pharmacotherapy) deliberately carry NO evidence item, with the reason in notes: no DSG2-specific trial exists and citing a general heart-failure trial would overstate what is known. NOT curated: datasets, biochemical, clinical_trials (Falcon found no DSG2-specific registered interventional trial), histopathology, definitions. Validation run and passed: validate, validate-terms, count-verified-snippets (73/73), check-duplicate-keys, check-entity-refs, check-causal-targets, check-qualifier-terms, check-enum-values, check-stubs, check-folded-hyphens, check-snippet-length, check-title-snippets, check-snippet-grading, check-environmental-evidence, and the batched validate-disorders gate.

Falcon ▸

Disease Characteristics Research Template

Edison Scientific Literature 31 citations 2026-09-01T16:29:10.612881

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on: 1. Key concepts and definitions with current understanding 2. Recent developments and latest research (prioritize 2023-2024 sources) 3. Current applications and real-world implementations 4. Expert opinions and analysis from authoritative sources 5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available. Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Disease Characteristics Research Template

Target Disease

Disease Name: Dilated Cardiomyopathy 1BB
MONDO ID: (if available)
Category: Genetic

Research Objectives

Please provide a comprehensive research report on Dilated Cardiomyopathy 1BB covering all of the disease characteristics listed below. This report will be used to populate a disease knowledge base entry. Be thorough and cite primary literature (PMID preferred) for all claims.

For each section, suggested databases/resources are listed. These are the first places you should search for information on each topic.

1. Disease Information

Search first: OMIM, Orphanet, ICD-10/ICD-11, MeSH, PubMed

What is the disease? Provide a concise overview.
What are the key identifiers? (OMIM, Orphanet, ICD-10/ICD-11, MeSH, Mondo)
What are the common synonyms and alternative names?
Is the information derived from individual patients (e.g., EHR) or aggregated disease-level resources?

2. Etiology

Disease Causal Factors: What are the primary causes? (genetic, environmental, infectious, mechanistic)
Risk Factors:

Search first: PubMed, Cochrane Library, UpToDate, clinical guidelines, ClinVar, ClinGen, GWAS Catalog, PheGenI, CTD, CDC, WHO, epidemiological databases
Genetic risk factors (causal variants, susceptibility loci, modifier genes)
Environmental risk factors (toxins, lifestyle, occupational exposures, age, sex, family history)
Protective Factors:

Search first: PubMed, Cochrane Library, clinical trial databases, GWAS Catalog, gnomAD, WHO, CDC, nutrition databases
Genetic protective factors (protective variants, modifier alleles)
Environmental protective factors (diet, lifestyle, exposures that reduce risk)
Gene-Environment Interactions: How do genetic and environmental factors interact to influence disease?

Search first: CTD, PubMed, PheGenI, GxE databases

3. Phenotypes

Search first: HPO (Human Phenotype Ontology), OMIM, Orphanet, PubMed, clinicaltrials.gov, MedDRA, SNOMED CT, DECIPHER, LOINC

For each phenotype, provide: - Phenotype type: symptoms, clinical signs, physical manifestations, behavioral changes, or laboratory abnormalities

For symptoms/signs: HPO, OMIM, Orphanet, PubMed For behavioral changes: HPO, DSM, RDoC (Research Domain Criteria), PubMed For laboratory abnormalities: LOINC, SNOMED CT, LabTests Online, PubMed - Phenotype characteristics: Search first: OMIM, Orphanet, HPO, PubMed - Age of symptom onset (neonatal, childhood, adult-onset, late-onset) - Symptom severity (mild, moderate, severe, variable) - Symptom progression (stable, progressive, episodic, fluctuating) - Frequency among affected individuals (percentage or qualitative) - Quality of life impact: Effects on daily functioning and well-being (per-phenotype when possible) Search first: EQ-5D database, SF-36, WHO QOL databases, PubMed - Suggest HPO (Human Phenotype Ontology) terms for each phenotype

4. Genetic/Molecular Information

Causal Genes: Gene mutations or chromosomal abnormalities responsible for disease (gene symbols, OMIM IDs)

Search first: OMIM, ClinVar, HGMD, Ensembl, NCBI Gene
Pathogenic Variants:
Affected genes (gene symbols, HGNC IDs) > Search first: OMIM, NCBI Gene, Ensembl, HGNC, UniProt, GeneCards
Variant classification (pathogenic, likely pathogenic, VUS per ACMG/AMP guidelines) > Search first: ClinVar, ClinGen, ACMG/AMP guidelines, VarSome
Variant type/class (missense, frameshift, nonsense, splice-site, structural)
Allele frequency in population databases > Search first: gnomAD, 1000 Genomes, ExAC, TOPMed, dbSNP
Somatic vs germline origin > Search first: COSMIC (somatic), ClinVar, ICGC, TCGA
Functional consequences (loss of function, gain of function, dominant negative)
Modifier Genes: Genes that modify disease severity or expression
Epigenetic Information: DNA methylation, histone modifications, chromatin changes affecting disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Chromosomal Abnormalities: Large-scale genetic changes (aneuploidy, translocations, inversions)

Search first: DECIPHER, ClinVar, ECARUCA, UCSC Genome Browser

5. Environmental Information

Environmental Factors: Non-genetic contributing factors (toxins, radiation, pollution, occupational exposure)

Search first: CTD (Comparative Toxicogenomics Database), TOXNET, PubMed, EPA databases
Lifestyle Factors: Behavioral factors (smoking, diet, exercise, alcohol consumption)

Search first: CDC databases, WHO, PubMed, NHANES
Infectious Agents: If applicable, pathogens causing or triggering disease (bacteria, viruses, fungi, parasites)

Search first: NCBI Taxonomy, ViPR, BV-BRC, MicrobeDB, GIDEON

6. Mechanism / Pathophysiology

Present this section as an ordered causal chain first, then the detail below. Open with a numbered sequence of mechanistic steps running from the initiating lesion (mutation, exposure, infection) to the clinical manifestation, one step per line, each naming what it causes next. State the causal verb explicitly ("leads to", "results in") and say where a step is inferred rather than demonstrated. Where the mechanism branches, show the branch. The categories below are a checklist of what to cover within those steps, not the organizing structure — a step may draw on several of them, and a category may contribute to several steps.

Molecular Pathways: Specific signaling cascades or biochemical pathways involved (Wnt, MAPK, mTOR, PI3K-AKT, etc.)

Search first: KEGG, Reactome, WikiPathways, PathBank, BioCyc
Cellular Processes: Cell-level mechanisms (apoptosis, autophagy, cell cycle dysregulation, inflammation, etc.)

Search first: Gene Ontology (GO), Reactome, KEGG, PubMed
Protein Dysfunction: How protein structure or function is altered (misfolding, aggregation, loss of function, gain of function)

Search first: UniProt, PDB (Protein Data Bank), InterPro, Pfam, AlphaFold
Metabolic Changes: Alterations in metabolic processes (energy metabolism, lipid metabolism, amino acid metabolism)

Search first: KEGG, BioCyc, HMDB (Human Metabolome Database), BRENDA
Immune System Involvement: Role of immune response (autoimmunity, immunodeficiency, chronic inflammation)

Search first: ImmPort, Immunome Database, IEDB, Gene Ontology
Tissue Damage Mechanisms: How tissues/ are injured (oxidative stress, ischemia, fibrosis, necrosis)

Search first: PubMed, Gene Ontology, Reactome
Biochemical Abnormalities: Specific molecular defects (enzyme deficiencies, receptor dysfunction, ion channel defects)

Search first: BRENDA, UniProt, KEGG, OMIM, PubMed
Epigenetic Changes: DNA methylation, histone modifications affecting gene expression in disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Molecular Profiling (if available):
Transcriptomics/gene expression changes > Search first: GEO (Gene Expression Omnibus), ArrayExpress, GTEx, Human Cell Atlas, SRA
Proteomics findings > Search first: PRIDE, ProteomeXchange, Human Protein Atlas, STRING, BioGRID
Metabolomics signatures > Search first: MetaboLights, Metabolomics Workbench, HMDB, METLIN
Lipidomics alterations > Search first: LIPID MAPS, SwissLipids, LipidHome, Metabolomics Workbench
Genomic structural features > Search first: UCSC Genome Browser, Ensembl, NCBI, dbVar, DGV
Advanced Technologies (if applicable):
Single-cell analysis findings (cell-type specific mechanisms, cellular heterogeneity) > Search first: Human Cell Atlas, Single Cell Portal, GEO, CELLxGENE
Spatial transcriptomics findings > Search first: GEO, Spatial Research, Vizgen, 10x Genomics data
Multi-omics integration results > Search first: TCGA, ICGC, cBioPortal, LinkedOmics, PubMed
Functional genomics screens (CRISPR, RNAi) > Search first: DepMap, GenomeRNAi, PubMed, BioGRID ORCS

For each mechanism, describe: - The causal chain from initial trigger to clinical manifestation - Which mechanisms are upstream vs downstream - What cell types and biological processes are involved - Suggest GO terms for biological processes and CL terms for cell types

7. Anatomical Structures Affected

Organ Level:
Primary organs directly affected
Secondary organ involvement (complications, secondary effects)
Body systems involved (cardiovascular, nervous, digestive, respiratory, endocrine, etc.)

Search first: Uberon, FMA (Foundational Model of Anatomy), OMIM, HPO, ICD-11, MeSH, SNOMED CT
Tissue and Cell Level:
Specific tissue types affected (epithelial, connective, muscle, nervous)
Specific cell populations targeted (with Cell Ontology terms)

Search first: Uberon, Human Protein Atlas, Cell Ontology, Human Cell Atlas, CellMarker, PanglaoDB
Subcellular Level:
Cellular compartments involved (mitochondria, nucleus, ER, lysosomes) (with GO Cellular Component terms)

Search first: Gene Ontology (Cellular Component), UniProt, Human Protein Atlas
Localization:
Specific anatomical sites (with UBERON terms) > Search first: FMA, Uberon, NeuroNames (for brain), SNOMED CT
Lateralization (unilateral, bilateral, asymmetric) > Search first: HPO, clinical literature, imaging databases

8. Temporal Development

Onset:
Typical age of onset (congenital, pediatric, adult, geriatric)
Onset pattern (acute, subacute, chronic, insidious)

Search first: OMIM, Orphanet, HPO, PubMed
Progression:
Disease stages (early, intermediate, advanced, end-stage) > Search first: Cancer Staging Manual (AJCC), WHO classifications, PubMed
Progression rate (rapid, slow, variable)
Disease course pattern (episodic, relapsing-remitting, progressive, stable)
Disease duration (self-limited, chronic lifelong)

Search first: Disease registries, longitudinal cohort databases, natural history studies, PubMed, Orphanet, OMIM
Patterns:
Remission patterns (spontaneous, treatment-induced) > Search first: Clinical trial databases, disease registries, PubMed
Critical periods (time windows of vulnerability or opportunity for intervention) > Search first: PubMed, developmental biology databases, clinical guidelines

9. Inheritance and Population

Epidemiology:
Prevalence (cases per 100,000 at given time)
Incidence (new cases per 100,000 per year)

Search first: Orphanet, CDC, WHO, GBD (Global Burden of Disease), national registries, SEER, disease registries
For Genetic Etiology:
Inheritance pattern (AD, AR, X-linked, mitochondrial, multifactorial, polygenic) > Search first: OMIM, Orphanet, ClinVar, GTR (Genetic Testing Registry)
Penetrance (complete, incomplete, age-dependent) > Search first: ClinVar, OMIM, PubMed, ClinGen
Expressivity (variable, consistent) > Search first: OMIM, ClinVar, PubMed
Genetic anticipation (increasing severity in successive generations) > Search first: OMIM, PubMed (especially for repeat expansion disorders)
Germline mosaicism > Search first: ClinVar, OMIM, genetic counseling literature, PubMed
Founder effects (population-specific mutations) > Search first: gnomAD, population genetics databases, PubMed
Consanguinity role > Search first: OMIM, population studies, genetic counseling resources
Carrier frequency > Search first: gnomAD, carrier screening databases, GeneReviews, GTR
Population Demographics:
Affected populations (ethnic or demographic groups with higher prevalence) > Search first: gnomAD, 1000 Genomes, PAGE Study, PubMed, population registries
Geographic distribution (endemic areas, regional variation) > Search first: WHO, CDC, GBD, Orphanet, geographic epidemiology databases
Geographic distribution of specific variants
Sex ratio (male:female) > Search first: Disease registries, OMIM, PubMed, epidemiological databases
Age distribution of affected individuals > Search first: CDC, disease registries, SEER, Orphanet

10. Diagnostics

Clinical Tests:
Laboratory tests (blood, urine, tissue chemistry, specific enzyme assays) > Search first: LOINC, LabTests Online, PubMed
Biomarkers (proteins, metabolites, genetic markers, circulating biomarkers) > Search first: FDA Biomarker List, BEST (Biomarkers, EndpointS, and other Tools), PubMed
Imaging studies (X-ray, CT, MRI, PET, ultrasound) > Search first: RadLex, DICOM, Radiopaedia, imaging databases
Functional tests (pulmonary function, cardiac stress tests) > Search first: LOINC, clinical guidelines, PubMed
Electrophysiology (EEG, EMG, ECG, nerve conduction studies) > Search first: LOINC, clinical neurophysiology databases, PubMed
Biopsy findings (histopathology, immunohistochemistry) > Search first: SNOMED CT, College of American Pathologists resources, PubMed
Pathology findings (microscopic examination) > Search first: SNOMED CT, Digital Pathology databases, PubMed
Genetic Testing:

Search first: GTR (Genetic Testing Registry), GeneReviews, ClinGen
Overview of recommended genetic testing approach
Whole genome sequencing (WGS) utility > Search first: GTR, ClinVar, GEL (Genomics England), gnomAD
Whole exome sequencing (WES) utility > Search first: GTR, ClinVar, OMIM, GeneMatcher
Gene panels (which panels, which genes) > Search first: GTR, ClinVar, laboratory-specific databases
Single gene testing > Search first: GTR, ClinVar, OMIM, GeneReviews
Chromosomal microarray (CMA) > Search first: DECIPHER, ClinVar, dbVar, ECARUCA
Karyotyping > Search first: Chromosome Abnormality Database, ClinVar, cytogenetics resources
FISH > Search first: ClinVar, cytogenetics databases, PubMed
Mitochondrial DNA testing > Search first: MITOMAP, MSeqDR, ClinVar, GTR
Repeat expansion testing > Search first: GTR, ClinVar, repeat expansion databases, PubMed
Omics-Based Diagnostics (if applicable):
RNA sequencing / transcriptomics > Search first: GEO, ArrayExpress, GTEx, RNA-seq databases
Proteomics > Search first: PRIDE, ProteomeXchange, FDA Biomarker database
Metabolomics > Search first: MetaboLights, Metabolomics Workbench, HMDB
Epigenomics > Search first: GEO, ENCODE, Roadmap Epigenomics, MethBase
Liquid biopsy > Search first: COSMIC, ClinVar, liquid biopsy databases, PubMed
Clinical Criteria:
Standardized diagnostic criteria (DSM, ICD, society guidelines) > Search first: DSM-5, ICD-11, clinical society guidelines, UpToDate
Differential diagnosis (other conditions to rule out, with distinguishing features) > Search first: DynaMed, UpToDate, clinical decision support systems
Screening:
Screening methods for asymptomatic individuals (newborn screening, carrier screening, cascade screening) > Search first: ACMG recommendations, CDC newborn screening, GTR

11. Outcome/Prognosis

Survival and Mortality:
Survival rate (5-year, 10-year, overall) > Search first: SEER, cancer registries, disease-specific registries, PubMed
Life expectancy (with and without treatment if applicable) > Search first: Orphanet, disease registries, actuarial databases, PubMed
Mortality rate > Search first: CDC, WHO, GBD, national mortality databases
Disease-specific mortality (deaths directly attributable to disease) > Search first: Disease registries, CDC Wonder, GBD, PubMed
Morbidity and Function:
Morbidity (disease-related disability and health impacts) > Search first: GBD, WHO, disability databases, PubMed
Disability outcomes (long-term functional impairments) > Search first: ICF (International Classification of Functioning), disability registries
Quality of life measures (EQ-5D, SF-36, PROMIS, disease-specific tools) > Search first: EQ-5D database, SF-36, PROMIS, PubMed
Disease Course:
Complications (secondary problems: infections, organ failure, etc.) > Search first: ICD codes, disease registries, clinical databases, PubMed
Recovery potential (likelihood and extent of recovery, with vs without treatment) > Search first: Natural history studies, rehabilitation databases, PubMed
Prediction:
Prognostic factors (age, disease severity, biomarkers, treatment response) > Search first: Prognostic models databases, clinical calculators, PubMed
Prognostic biomarkers (molecular markers predicting disease course) > Search first: FDA Biomarker database, PubMed, cancer prognostic databases

12. Treatment

Pharmacotherapy:
Pharmacological treatments (drug names, drug classes, mechanisms of action) > Search first: DrugBank, RxNorm, ATC classification, DailyMed, FDA databases
Pharmacogenomics (how genetic variants affect drug metabolism, efficacy, toxicity) > Search first: PharmGKB, CPIC (Clinical Pharmacogenetics), FDA Table of PGx Biomarkers
Advanced Therapeutics:
Gene therapy (viral vectors, CRISPR, gene replacement, gene editing) > Search first: ClinicalTrials.gov, FDA gene therapy database, ASGCT resources
Cell therapy (stem cell transplant, CAR-T, cellular therapeutics) > Search first: ClinicalTrials.gov, FDA cell therapy database, FACT standards
RNA-based therapies (ASOs, siRNA, mRNA therapies) > Search first: ClinicalTrials.gov, FDA approvals, PubMed
Targeted therapies (treatments directed at specific molecular targets) > Search first: My Cancer Genome, OncoKB, ClinicalTrials.gov, FDA approvals
Immunotherapies (checkpoint inhibitors, monoclonal antibodies) > Search first: Cancer Immunotherapy Database, FDA approvals, ClinicalTrials.gov
Surgical and Interventional:
Surgical interventions (types of surgery, timing, outcomes) > Search first: CPT codes, surgical registries, clinical guidelines, PubMed
Supportive and Rehabilitative:
Supportive care (symptom management, pain control, nutrition) > Search first: Clinical guidelines, Cochrane Library, PubMed
Rehabilitation (physical therapy, occupational therapy, speech therapy) > Search first: Rehabilitation medicine databases, clinical guidelines, PubMed
Experimental:
Experimental treatments in clinical trials (with NCT identifiers if available) > Search first: ClinicalTrials.gov, EU Clinical Trials Register, WHO ICTRP
Treatment Outcomes:
Treatment response rates > Search first: Clinical trial databases, FDA reviews, systematic reviews, PubMed
Side effects and adverse events > Search first: FDA Adverse Event Reporting System (FAERS), MedWatch, PubMed
Treatment Strategy:
Treatment algorithms (clinical pathways, decision trees) > Search first: Clinical practice guidelines, NCCN Guidelines, UpToDate
Combination therapies > Search first: ClinicalTrials.gov, treatment guidelines, PubMed
Personalized medicine approaches (genotype-guided treatment) > Search first: My Cancer Genome, CIViC, PharmGKB, precision medicine databases

For each treatment, suggest NCIT (NCI Thesaurus) clinical-intervention terms where applicable.

13. Prevention

Prevention Levels:
Primary prevention (preventing disease occurrence: vaccination, risk factor modification) > Search first: CDC, WHO, USPSTF recommendations, Cochrane Library
Secondary prevention (early detection and treatment: screening programs, early intervention) > Search first: USPSTF, CDC screening guidelines, WHO
Tertiary prevention (preventing complications in those with disease) > Search first: Clinical guidelines, disease management protocols, PubMed
Immunization: Vaccine strategies (if applicable)

Search first: CDC vaccine schedules, WHO immunization, FDA vaccine database
Screening and Early Detection:
Screening programs (population-based: newborn screening, cancer screening) > Search first: CDC screening programs, USPSTF, cancer screening databases
Genetic screening (carrier screening, preimplantation genetic diagnosis, prenatal testing) > Search first: ACMG recommendations, ACOG guidelines, GTR
Risk stratification (identifying high-risk individuals for targeted prevention) > Search first: Risk prediction models, clinical calculators, PubMed
Behavioral Interventions: Lifestyle modifications to reduce risk

Search first: CDC, WHO, behavioral intervention databases, Cochrane Library
Counseling: Genetic counseling (risk assessment, family planning guidance)

Search first: NSGC resources, ACMG guidelines, GeneReviews
Public Health:
Public health interventions (sanitation, vector control, health education) > Search first: CDC, WHO, public health databases, PubMed
Environmental interventions (reducing environmental risk factors) > Search first: EPA databases, WHO environmental health, PubMed
Prophylaxis: Preventive medications or procedures

Search first: Clinical guidelines, FDA approvals, PubMed

14. Other Species / Natural Disease

Taxonomy: Species affected (with NCBI Taxon identifiers)

Search first: NCBI Taxonomy
Breed: Specific breeds affected (with VBO identifiers if applicable)

Search first: VBO (Vertebrate Breed Ontology)
Gene: Orthologous genes in other species (with NCBI Gene IDs)

Search first: NCBI Gene
Natural Disease:
Naturally occurring disease in other species (companion animals, wildlife) > Search first: OMIA (Online Mendelian Inheritance in Animals), VetCompass, PubMed
Veterinary relevance and importance in animal health > Search first: OMIA, veterinary databases, PubMed
Comparative Biology:
Comparative pathology (similarities and differences across species) > Search first: OMIA, comparative pathology databases, PubMed
Evolutionary conservation of disease mechanisms > Search first: HomoloGene, OrthoMCL, Alliance of Genome Resources
Transmission (if applicable):
Zoonotic potential > Search first: CDC zoonotic diseases, WHO zoonoses, GIDEON
Cross-species susceptibility > Search first: NCBI Taxonomy, veterinary databases, PubMed

15. Model Organisms

Model Types:
Model organism type (mammalian, invertebrate, cellular, in vitro) > Search first: Alliance of Genome Resources, model organism databases
Specific model systems (mouse, rat, zebrafish, Drosophila, C. elegans, yeast, cell lines, organoids, iPSCs) > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, SGD, ATCC, Cellosaurus
Induced models (drug treatment, surgical intervention, environmental manipulation) > Search first: MGI, model organism databases, PubMed
Genetic Models:
Types available (knockout, knock-in, transgenic, conditional, humanized) > Search first: MGI, IMPC, KOMP, EuMMCR, IMSR
Model Characteristics:
Phenotype recapitulation (how well model reproduces human disease features) > Search first: Model organism databases, comparative studies, PubMed
Model limitations (aspects of human disease not captured) > Search first: Model organism databases, PubMed, review articles
Applications:
Research applications (what aspects of disease can be studied) > Search first: Model organism databases, PubMed
Resources:
Model databases > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, IMSR, EMMA, MMRRC

Citation Requirements

Cite primary literature (PMID preferred) for all mechanistic and clinical claims
Prioritize recent reviews and landmark papers
Include direct quotes from abstracts where possible to support key statements
Distinguish evidence source types: human clinical, model organism, in vitro, computational

Output Format

Structure your response as a comprehensive narrative organized by the sections above. For each section, provide: - Factual content with specific details (numbers, percentages, gene names, variant nomenclature) - Ontology term suggestions (HPO, GO, CL, UBERON, CHEBI, NCIT, MONDO) where applicable - Evidence citations with PMIDs - Direct quotes from abstracts to support key claims - Clear indication when information is not available or not applicable for this disease

This report will be used to populate a disease knowledge base entry with: - Pathophysiology descriptions with causal chains - Gene/protein annotations (HGNC, GO terms) - Phenotype associations (HP terms) with frequencies - Cell type involvement (CL terms) - Anatomical locations (UBERON terms) - Chemical entities (CHEBI terms) - Treatment annotations (NCIT terms) - Evidence items with PMIDs and exact abstract quotes - Epidemiology, prognosis, diagnostic, and prevention information - Animal model descriptions with phenotype recapitulation details

Dilated Cardiomyopathy 1BB (DSG2-associated cardiomyopathy): comprehensive disease-characteristics report

Executive summary and scope

Dilated cardiomyopathy 1BB (DCM1BB) is a rare genetic cardiomyopathy associated with DSG2, which encodes the desmosomal cadherin desmoglein-2. The specific ontology entry is MONDO:0013030. Modern evidence indicates substantial overlap among DSG2-associated dilated, biventricular, and arrhythmogenic cardiomyopathy phenotypes; therefore, “DCM1BB” should not be treated as a completely discrete clinicopathological entity. Direct DCM1BB evidence is limited, and much of the mechanistic and natural-history evidence comes from broader DSG2-associated arrhythmogenic cardiomyopathy (ACM), human myocardial specimens, induced pluripotent stem-cell cardiomyocytes (iPSC-CMs), and Dsg2 mouse models. Open Targets links MONDO:0013030 specifically to DSG2 and cites supporting literature including PMIDs 18678517, 23500315, 27532257, and 29567486. (OpenTargets Search: Dilated cardiomyopathy 1BB)

The strongest current interpretation is that pathogenic DSG2 variants impair cardiomyocyte–cardiomyocyte adhesion and intercalated-disc organization, producing electrical instability, cardiomyocyte injury, inflammation, fibrosis, ventricular dilation, and systolic failure. Monoallelic variants often have incomplete, age-dependent penetrance and can require genetic or environmental modifiers; biallelic loss-of-function or severe missense genotypes generally produce earlier and more severe biventricular disease. (shiba2021phenotypicrecapitulationand pages 2-3, pinci2026integrativegenomicand pages 1-6, zhang2024hyperactivationofatf4tgfβ1 pages 1-2, sumida2024fourcardiomyopathypatients pages 1-2)

The following evidence map summarizes the distinction between direct DCM1BB evidence and broader DSG2-ACM extrapolation.

Domain	Disease-specific finding	Evidence type	Key quantitative detail	Source/year
Identity	Dilated cardiomyopathy 1BB is mapped to MONDO:0013030 and linked to DSG2 (desmoglein-2); evidence base is small and overlaps strongly with broader DSG2-associated arrhythmogenic cardiomyopathy literature	Curated disease-target association	1 disease-target association listed for DCM1BB: DSG2	Open Targets disease-target mapping (OpenTargets Search: Dilated cardiomyopathy 1BB)
Human genetics: p.Arg119Ter	Heterozygous DSG2 p.Arg119Ter occurs in cardiomyopathy patients with variable phenotypes including DCM; supports desmosomal impairment as a contributor/exacerbator rather than proving fully penetrant monogenic DCM1BB alone	Human cohort/case series	4 unrelated carriers among 808 nonischemic cardiomyopathy patients; cohort allele frequency 0.0037; described as >50-fold above general Japanese population; diagnoses included ARVC, DCM after VSD repair, DCM, end-stage HCM	Sumida et al., 2024 (sumida2024fourcardiomyopathypatients pages 1-2)
Human genetics: p.Phe531Cys family	Homozygous DSG2 p.Phe531Cys / F531C segregated with severe familial ACM featuring fibrosis/dysfunction; highly informative for DSG2 biology, but broader ACM evidence rather than direct DCM1BB nomenclature	Human family study + knock-in model	8 affected family members, all homozygous; desmosomal-gene variants account for ~two-thirds of ACM; DSG2 described as second most prevalent ACM gene	Zhang et al., 2024 (zhang2024hyperactivationofatf4tgfβ1 pages 1-2)
Human cellular disease model	Complete DSG2 deficiency can present clinically as severe juvenile-onset biventricular cardiomyopathy diagnosed as idiopathic DCM, supporting DSG2-deficient DCM as a real disease mechanism	Human case + iPSC-derived cardiomyocytes	Homozygous c.355C>T (p.R119X); VAD implantation at age 21; heterozygous parents unaffected; mutant tissue-ring force reduced and corrected after repair	Shiba et al., 2021 (shiba2021phenotypicrecapitulationand pages 2-3, shiba2021phenotypicrecapitulationand pages 1-1)
iPSC correction / AAV rescue	Disease phenotypes from DSG2 deficiency were reversed by isogenic correction and improved by AAV-mediated DSG2 replacement, providing preclinical precision-medicine proof of concept	Human iPSC-CM and engineered tissue	Contractile force improved from 49 ± 6 to 86 ± 1 μN after correction; AAV-mediated DSG2 replacement significantly recovered contraction force	Shiba et al., 2021 (shiba2021phenotypicrecapitulationand pages 10-11, shiba2021phenotypicrecapitulationand pages 1-1)
2024 immune mechanism	In DSG2-mutant mouse ACM, NFκB signaling in cardiomyocytes recruits CCR2+ macrophages, driving myocardial injury, dysfunction, arrhythmias, and fibro-inflammatory remodeling; mechanistically relevant but preclinical and broader ACM	Mouse genetics + single-nucleus/single-cell profiling	Disease prevented/attenuated when cardiac-myocyte NFκB signaling was blocked; snRNA-seq/CITE-seq implicated cardiomyocytes, fibroblasts, and CCR2+ macrophages	Chelko et al., 2024 (chelko2024nfĸbsignalingdrives pages 1-2)
2024 fibrosis mechanism	Variant DSG2 protein can misfold in the ER, activate BiP → PERK → ATF4 → TGF-β1, and stimulate fibroblasts paracrinally, explaining progressive fibrosis in DSG2 cardiomyopathy	Human family-supported mouse/mechanistic study	Inhibition of PERK-ATF4 attenuated fibrosis and systolic dysfunction in Dsg2F536C/F536C mice	Zhang et al., 2024 (zhang2024hyperactivationofatf4tgfβ1 pages 1-2)
2024 exercise interaction	Endurance training can unmask a right-ventricular arrhythmogenic phenotype in heterozygous Dsg2 mice; relevant gene-environment interaction for DSG2 disease counseling	Mouse exercise model	DSG2 mutations reported in 5–10% of ARVC; training increased RV diameter, decreased RV function, prolonged activation times, and induced pacing-triggered arrhythmia without obvious fibrosis/inflammation	Fabritz et al., 2024 (sumida2024fourcardiomyopathypatients pages 1-2)
Diagnostic implementation	Current care relies on phenotype-first cardiomyopathy workup with echocardiography, CMR, ECG/Holter, biomarkers, pedigree analysis, and genetic testing/counseling; DCM1BB has no standalone diagnostic criteria beyond inherited cardiomyopathy practice	Guideline/review	Genetic testing is described as a first-tier diagnostic test for every patient with DCM; CMR is gold standard for fibrosis/phenotyping; imaging + genetics guide ICD decisions	Stroeks et al., 2023; Grasso et al., 2024; Gasior, 2024 (stroeks2023diagnosticandprognostic pages 1-2, grasso2024thenew2023 pages 1-2, gasior2024advancesincardiac pages 1-2)
Epidemiology caveat	There are no subtype-specific prevalence/incidence data for DCM1BB; only broader DCM/ACM estimates are available, so population burden must be inferred cautiously	Review / broader disease epidemiology	ACM prevalence estimated 1:2000–1:5000; DCM prevalence estimated ~1:220 to 1:250 in modern datasets, far higher than older ~1:2500 estimates	Vencato et al., 2024; Newman & Burke, 2024 (vencato2024animalmodelsand pages 1-2, newman2024dilatedcardiomyopathya pages 1-2)
Therapy status	No DSG2-specific approved therapy and no DSG2-specific registered interventional clinical trial were identified; current treatment remains standard HF/arrhythmia management, while gene therapy evidence is preclinical	Clinical-trial search + literature	Identified ACM trials were observational or targeted other genes/inflammatory pathways (e.g., PKP2 gene therapy), not DSG2-specific	Clinical-trial search context + field literature (OpenTargets Search: Dilated cardiomyopathy 1BB)

Table: This table summarizes the most decision-relevant evidence for DSG2-associated dilated cardiomyopathy 1BB, distinguishing direct DCM1BB findings from broader DSG2-arrhythmogenic cardiomyopathy data. It is useful for rapidly identifying what is established in humans, what remains preclinical, and where evidence gaps persist.

1. Disease information

Definition

DCM is defined clinically by left-ventricular or biventricular dilation and systolic dysfunction not sufficiently explained by coronary artery disease or abnormal loading conditions such as hypertension or valvular disease. The 2023 ESC framework defines cardiomyopathies as myocardial disorders with structural or functional abnormality in the absence of coronary, hypertensive, valvular, or congenital disease sufficient to explain it. (grasso2024thenew2023 pages 1-2, stroeks2023diagnosticandprognostic pages 1-2)

DCM1BB denotes the DSG2-associated genetic form. Because DSG2 disease often combines dilation, fibrosis, ventricular arrhythmias, and right-ventricular involvement, affected patients may instead receive diagnoses of DCM, arrhythmogenic right-ventricular cardiomyopathy (ARVC), arrhythmogenic biventricular cardiomyopathy, or end-stage cardiomyopathy. A 2024 series found the same heterozygous p.Arg119Ter allele among patients diagnosed with ARVC, two forms of DCM, and end-stage hypertrophic cardiomyopathy, illustrating this phenotypic continuum. (sumida2024fourcardiomyopathypatients pages 1-2)

Identifiers and synonyms

MONDO: MONDO:0013030.
Causal gene: DSG2, desmoglein-2; Ensembl ENSG00000046604. (OpenTargets Search: Dilated cardiomyopathy 1BB)
Common names: dilated cardiomyopathy 1BB; DCM1BB; DSG2-related dilated cardiomyopathy; desmoglein-2 cardiomyopathy; DSG2-associated cardiomyopathy.
Overlapping clinical terms: DSG2-related arrhythmogenic cardiomyopathy, arrhythmogenic right-ventricular cardiomyopathy, biventricular arrhythmogenic cardiomyopathy.
Broader coding: ICD-10-CM I42.0, dilated cardiomyopathy; I42.8/I42.9 may be used depending on local phenotype and coding practice. ICD-11 and MeSH generally classify the phenotype under dilated or arrhythmogenic cardiomyopathy rather than a DCM1BB-specific code.
OMIM/Orphanet: A separate subtype-level identifier was not verified in the retrieved full-text evidence. Knowledge-base implementations should retain MONDO:0013030 and link DSG2-associated ARVC/ACM records rather than infer an unverified number.

This report synthesizes aggregated disease resources and published cohorts, not individual EHR records. Some primary evidence derives from individual patients or families, notably the homozygous p.Arg119Ter patient and the p.Phe531Cys pedigree. (shiba2021phenotypicrecapitulationand pages 2-3, zhang2024hyperactivationofatf4tgfβ1 pages 1-2)

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

Causal factors

The initiating lesion is a germline pathogenic or likely pathogenic variant in DSG2. Desmoglein-2 is a calcium-dependent transmembrane cadherin at cardiac desmosomes and the area composita of intercalated discs. DSG2 and desmocollin-2 connect neighboring cardiomyocytes extracellularly and anchor through armadillo/plakin proteins to the cytoskeleton. (vencato2024animalmodelsand pages 1-2)

Disease-associated classes include missense substitutions affecting extracellular calcium-binding or adhesive domains, premature-termination variants, splice variants, frameshifts, and copy-number loss. Functional consequences vary and include reduced abundance, nonsense-mediated decay/haploinsufficiency, complete deficiency in biallelic loss, dominant-negative adhesive dysfunction, protein misfolding, and impaired cytoskeletal anchoring. (pinci2026integrativegenomicand pages 26-31, shiba2021phenotypicrecapitulationand pages 2-3, zhang2024hyperactivationofatf4tgfβ1 pages 1-2)

Genetic risk factors and modifiers

Allele dosage: Biallelic or multilocus genotypes are associated with earlier onset, greater biventricular involvement, and more complete penetrance than isolated monoallelic variants. (pinci2026integrativegenomicand pages 1-6)
Second variants: In the 2024 p.Arg119Ter series, one patient also carried DSG2 p.Arg292Cys and another carried BAG3 p.His166SerfsTer6, supporting oligogenic modification. (sumida2024fourcardiomyopathypatients pages 1-2)
Variant location: Extracellular calcium-binding residues, the furin-cleavage region, and intracellular PKP2-binding/cytoskeletal anchoring regions are enriched for clinically important variants. (pinci2026integrativegenomicand pages 26-31)
General DCM architecture: Up to 40% of idiopathic DCM may be attributable to a core set of causal genes, but more than 200 genes have been reported and evidence for many is weak. This cautions against attributing disease to a DSG2 VUS without segregation or functional evidence. (newman2024dilatedcardiomyopathya pages 1-2, stroeks2023diagnosticandprognostic pages 1-2)

Environmental and lifestyle risk factors

High-intensity or endurance exercise is the best-supported environmental accelerator for desmosomal ACM. A 2024 review reports up to a fivefold greater sudden-death risk in affected athletes, although this estimate is for ACM generally and is not DCM1BB-specific. (vencato2024animalmodelsand pages 1-2)

Sports, hypertension, diabetes, obesity, pregnancy, and toxic exposures can modulate dilation, dysfunction, and arrhythmia expression in cardiomyopathy broadly. Alcohol, cardiotoxic chemotherapy, myocarditis/infection, nutritional deficiency, and autoimmune disease are important alternative or interacting causes of DCM and should be assessed rather than assumed causal in an individual DSG2 carrier. (newman2024dilatedcardiomyopathya pages 1-2, gasior2024advancesincardiac pages 1-2)

The 2024 p.Arg119Ter investigators explicitly concluded that desmosomal impairment combined with additional genetic or environmental factors may promote dysfunction. In Dsg2 heterozygous mice, endurance training increased right-ventricular size, reduced right-ventricular function, prolonged activation, and increased inducible ventricular arrhythmia, supporting a mechanically mediated gene–exercise interaction, although translation to humans remains inferential. (sumida2024fourcardiomyopathypatients pages 1-2)

Protective factors

No validated protective DSG2 allele, diet, supplement, or chemopreventive agent is established. Avoidance of competitive/high-intensity endurance exercise is the principal modifiable protective strategy extrapolated from ACM data. Control of hypertension, obesity, diabetes, alcohol exposure, and cardiotoxic drugs plausibly reduces additional myocardial stress but has not been quantified specifically for DCM1BB. Preload reduction prevented exercise-induced disease features in heterozygous Dsg2 mice, but this remains preclinical. (gasior2024advancesincardiac pages 1-2, vencato2024animalmodelsand pages 1-2)

3. Phenotypes

The phenotype is heterogeneous, age-dependent, and progressive. Frequencies below are generally unavailable for DCM1BB specifically.

Manifestation	Type/course	Suggested HPO term
Left-ventricular dilation	Imaging sign; progressive/variable	HP:0001644, Dilated cardiomyopathy
Reduced LV systolic function	Imaging/functional abnormality	HP:0001686, Loss of left ventricular function
Biventricular dilation/dysfunction	Severe structural-functional sign; common in biallelic cases	HP:0001717, Right ventricular dilatation; HP:0001644
Heart failure	Symptom/sign; exertional limitation to end-stage failure	HP:0001635, Congestive heart failure
Ventricular arrhythmia/tachycardia	Electrophysiological sign; may precede dilation	HP:0004308, Ventricular arrhythmia; HP:0004756, Ventricular tachycardia
Palpitations, syncope	Symptoms, episodic	HP:0001962, Palpitations; HP:0001279, Syncope
Sudden cardiac arrest/death	Severe outcome; sometimes first manifestation in ACM spectrum	HP:0001699, Sudden death
Myocardial fibrosis/scarring	CMR/pathology finding; progressive	HP:0001685, Myocardial fibrosis
Abnormal ECG/conduction	Electrophysiological sign	HP:0003115, Abnormal EKG; HP:0031546, Abnormal cardiac conduction
Cardiomegaly	Imaging/physical sign	HP:0001640, Cardiomegaly
Exercise intolerance/dyspnea/fatigue	Symptoms affecting daily activity	HP:0003546, Exercise intolerance; HP:0002094, Dyspnea; HP:0012378, Fatigue

The homozygous p.Arg119Ter case was normal at birth but developed juvenile-onset severe biventricular failure, uncontrolled ventricular arrhythmia, progressive dilation, and required ventricular-assist-device implantation at 21 years. Both heterozygous parents were reportedly unaffected, supporting recessive severe disease for complete deficiency. (shiba2021phenotypicrecapitulationand pages 9-10, shiba2021phenotypicrecapitulationand pages 2-3)

Quality-of-life studies specific to DCM1BB were not found. Expected impacts include reduced exercise capacity, medication and surveillance burden, driving/employment restrictions after arrhythmia, ICD shocks, hospitalization, and advanced-HF disability. These are extrapolated from DCM/ACM rather than measured with EQ-5D or SF-36 in DCM1BB.

4. Genetic and molecular information

Gene and protein

DSG2 encodes desmoglein-2, a calcium-binding desmosomal cadherin enriched in myocardium. The protein spans extracellular cadherin domains, a transmembrane region, and a cytoplasmic region that participates in desmosomal assembly and linkage to plakoglobin/plakophilin/desmoplakin and the intermediate-filament cytoskeleton. (pinci2026integrativegenomicand pages 26-31, vencato2024animalmodelsand pages 1-2)

Suggested annotations include GO:0007155 cell adhesion, GO:0098609 cell–cell adhesion, GO:0005916 fascia adherens, GO:0030057 desmosome, GO:0005911 cell–cell junction, and GO:0009986 cell surface.

Representative variants

NM_001943.5:c.355C>T, p.Arg119Ter (R119X): stop-gain. Homozygosity caused complete DSG2 deficiency and severe juvenile biventricular cardiomyopathy. Heterozygous pathogenicity is less certain and may act as an incompletely penetrant risk/exacerbating allele. (shiba2021phenotypicrecapitulationand pages 2-3, sumida2024fourcardiomyopathypatients pages 1-2)
p.Phe531Cys (F531C; reported c.1592T>G): homozygous missense variant in a five-generation family with eight affected members. The protein misfolded and activated ER-stress signaling in the corresponding knock-in model. (zhang2024hyperactivationofatf4tgfβ1 pages 1-2)
p.Asn266Ser: experimentally associated with dose-dependent dominant-negative disease and provides foundational mechanistic evidence, although the retrieved primary support is mainly in the broader DSG2-ACM literature.
Other reported truncating examples include E418fsX419, G678fsX681, and Q558X. (shiba2021phenotypicrecapitulationand pages 10-11)
Copy-number variants and compound heterozygous combinations may be especially severe; complete deletion/splice combinations have been described in recessive early-onset ACM.

In the 2024 Japanese study, p.Arg119Ter had a worldwide gnomAD MAF of approximately 9.297×10⁻⁶; reported counts included 9/44,826 East-Asian alleles and 6/1,179,852 non-Finnish European alleles. Japanese jMorp frequency was 7/108,574, approximately 6.9-fold above total gnomAD. Among 808 nonischemic-cardiomyopathy patients, four unrelated carriers produced a study allele frequency of 0.0037, described as over 50-fold above the general Japanese population. (sumida2024fourcardiomyopathypatients pages 1-2)

All known causal variants are germline; no somatic DSG2 mechanism is established for DCM1BB. Variant assertions should follow ACMG/AMP criteria with ClinGen disease-specific evidence, segregation, population frequency, transcript consequence, and functional studies. A VUS must not be used alone for predictive cascade testing or irreversible management decisions. Expanded testing from 48 to 299 genes in 225 panel-negative DCM patients produced many VUSs—186 in 127 patients—but only one newly found variant clearly explained phenotype, supporting focused use of robust genes and careful VUS interpretation. (stroeks2023diagnosticandprognostic pages 1-2)

Epigenetics and structural abnormalities

No reproducible DCM1BB-specific DNA-methylation, histone, chromatin, aneuploidy, translocation, or inversion signature is established. DSG2 deletions/CNVs are relevant and require CNV-capable sequencing or array analysis. Epigenetic findings in generic DCM/ACM should not be entered as DCM1BB-specific without direct evidence.

5. Environmental information

There is no infectious agent, toxin, radiation exposure, or occupational exposure that independently causes DCM1BB. Viral myocarditis, alcohol, cocaine/amphetamines, anthracyclines, trastuzumab, nutritional deficiency, pregnancy, and autoimmune disease are clinically important triggers, modifiers, or differentials for a DSG2 carrier. The evidence for a direct DSG2-specific interaction is strongest for mechanical load/endurance exercise. (newman2024dilatedcardiomyopathya pages 1-2, gasior2024advancesincardiac pages 1-2, vencato2024animalmodelsand pages 1-2)

Smoking cessation, moderation/avoidance of alcohol, weight and blood-pressure control, vaccination and infection prevention, and avoidance of nonessential cardiotoxins follow general heart-failure prevention principles. They are sensible but not demonstrated as genotype-specific protective interventions.

6. Mechanism and pathophysiology

Ordered causal chain

A pathogenic germline DSG2 variant leads to reduced, absent, mislocalized, structurally unstable, or misfolded desmoglein-2.
Altered desmoglein-2 leads to defective calcium-dependent desmosomal adhesion and disturbed assembly of the intercalated disc/area composita.
Junctional disruption leads to reduced mechanical cohesion during contraction and secondary abnormalities in desmocollin-2, desmoplakin, connexin-43, and electrical coupling; some channel effects remain inferred rather than demonstrated in every human genotype. (shiba2021phenotypicrecapitulationand pages 10-11, shiba2021phenotypicrecapitulationand pages 1-1, vencato2024animalmodelsand pages 1-2, sumida2024fourcardiomyopathypatients pages 1-2)
Mechanical and electro-coupling failure leads to two interacting branches:
Branch A: conduction slowing and heterogeneous propagation lead to ventricular ectopy, tachycardia, syncope, and sudden-death risk;
Branch B: mechanical stress and tissue fragility lead to cardiomyocyte apoptosis/necrosis and loss of contractile myocardium.
Cardiomyocyte injury leads to release of damage signals and cardiomyocyte-intrinsic NF-κB activation, which results in CCL2/CCR2-positive monocyte/macrophage recruitment and fibro-inflammatory crosstalk; this is strongly demonstrated in Dsg2 mice and supported in patient-derived iPSC-CMs. (chelko2024nfĸbsignalingdrives pages 1-2)
In susceptible missense variants, DSG2 misfolding leads to BiP recognition and ER stress, which activates PERK–ATF4 signaling; ATF4 increases cardiomyocyte TGF-β1, which activates fibroblasts by paracrine signaling. This branch is demonstrated for p.Phe531Cys/F531C and should not automatically be generalized to all variants. (zhang2024hyperactivationofatf4tgfβ1 pages 1-2)
Inflammation, TGF-β signaling, and repair lead to replacement/interstitial fibrosis and, in the ACM spectrum, possible fibrofatty remodeling. Wnt/β-catenin inhibition with Hippo and TGF-β activation is supported mainly by animal models and remains partly inferential for human DCM1BB. (zhang2024hyperactivationofatf4tgfβ1 pages 1-2, vencato2024animalmodelsand pages 1-2, chelko2024nfĸbsignalingdrives pages 1-2)
Myocyte loss plus fibrosis leads to reduced force, chamber dilation, neurohormonal activation, and progressive left- or biventricular systolic failure.
Fibrosis and ventricular dilation further lead to electrical heterogeneity, valvular regurgitation, thromboembolic risk, end-stage heart failure, transplantation/VAD requirement, or death.
Endurance exercise and other hemodynamic stressors lead to greater junctional load and can accelerate the electrical and structural branches in genetically susceptible individuals. (vencato2024animalmodelsand pages 1-2)

Human tissue and cellular evidence

The p.Arg119Ter patient’s myocardium showed abnormal cytoplasmic deposition of desmosomal proteins, disrupted intercalated discs, vacuoles, and absent desmoglein-2 staining. Patient-derived iPSC-CMs reproduced abnormal excitation, disrupted desmosomes, tissue fragility, and weak force. Isogenic HDR correction restored DSG2 expression and improved force from approximately 49±6 to 86±1 μN in engineered tissue, establishing causality at the cellular level. AAV-mediated DSG2 replacement also improved contraction. (shiba2021phenotypicrecapitulationand pages 10-11, shiba2021phenotypicrecapitulationand pages 2-3, shiba2021phenotypicrecapitulationand pages 1-1)

A direct abstract quotation is: “Adeno-associated virus-mediated replacement of DSG2 significantly recovered the contraction force” in patient-derived tissue rings. This is proof of concept, not evidence of human therapeutic safety or efficacy. (shiba2021phenotypicrecapitulationand pages 10-11)

2024 mechanistic advances

Zhang et al. connected DSG2 protein misfolding to fibrosis through BiP–PERK–ATF4–TGF-β1. Their abstract states: “Increased ATF4 facilitated the expression of TGF-β1 in cardiomyocytes, thereby activating cardiac fibroblasts through paracrine signaling.” Pharmacological/genetic pathway inhibition attenuated fibrosis and systolic dysfunction in knock-in mice. Published September 2024, DOI: https://doi.org/10.1186/s12916-024-03593-8. (zhang2024hyperactivationofatf4tgfβ1 pages 1-2)

Chelko et al. used genetic perturbation, single-nucleus RNA-seq, and CITE-seq in Dsg2-mutant mice. Their central result was that cardiomyocyte NF-κB mobilizes CCR2-positive macrophages, which mediate injury and arrhythmia; transcriptional changes involved cardiomyocytes, fibroblasts, and macrophages. Published April 2, 2024, DOI: https://doi.org/10.1172/JCI172014. This is advanced preclinical evidence, not yet a validated treatment pathway in people. (chelko2024nfĸbsignalingdrives pages 1-2)

Suggested GO terms include GO:0007155 cell adhesion, GO:0007162 negative regulation of cell adhesion, GO:0008219 cell death, GO:0006915 apoptotic process, GO:0006954 inflammatory response, GO:0006955 immune response, GO:0062023 collagen-containing extracellular matrix organization, GO:0048771 tissue remodeling, GO:0030199 collagen fibril organization, GO:0034976 response to endoplasmic-reticulum stress, GO:0006986 response to unfolded protein, GO:0030511 positive regulation of TGF-β receptor signaling, and GO:0060048 cardiac muscle contraction.

Suggested Cell Ontology annotations are CL:0000746 cardiac muscle cell/cardiomyocyte, CL:0000057 fibroblast, CL:0000863 inflammatory macrophage, CL:0000235 macrophage, CL:0000576 monocyte, CL:0000775 neutrophil, and cardiac conduction-system cardiomyocyte terms where supported.

7. Anatomical structures affected

The primary organ is the heart (UBERON:0000948), particularly ventricular myocardium (UBERON:0002349 myocardium), left ventricle (UBERON:0002084), right ventricle (UBERON:0002080), and interventricular/biventricular myocardium. Disease is not inherently lateralized. Intercalated discs and desmosomes are the principal subcellular sites; the ER is additionally implicated for misfolding variants. (zhang2024hyperactivationofatf4tgfβ1 pages 1-2, vencato2024animalmodelsand pages 1-2)

At tissue level, cardiomyocytes are primarily injured, with secondary activation of resident/recruited macrophages and cardiac fibroblasts. At organ level, advanced low-output failure can secondarily affect lungs, liver, kidneys, skeletal muscle, and brain through congestion, hypoperfusion, embolism, or arrhythmic syncope; these are complications rather than primary DSG2 targets.

Suggested GO cellular components are GO:0030057 desmosome, GO:0030018 Z disc where relevant, GO:0005911 cell–cell junction, GO:0070161 anchoring junction, GO:0005783 endoplasmic reticulum, GO:0005886 plasma membrane, and GO:0030315 T-tubule only if specifically demonstrated.

8. Temporal development

Onset ranges from juvenile to adult and may be insidious. A “concealed” electrical phase can precede overt dilation or systolic failure. Biallelic loss can present early and progress rapidly, whereas heterozygous carriers may remain asymptomatic for decades or develop arrhythmia, fibrosis, or systolic dysfunction later. The homozygous p.Arg119Ter patient was normal at birth, developed juvenile disease, and required VAD support by 21; this suggests postnatal mechanical load can expose deficient junctional reserve. (shiba2021phenotypicrecapitulationand pages 9-10, shiba2021phenotypicrecapitulationand pages 2-3)

A practical temporal model is: genotype-positive/phenotype-negative → early ECG or CMR abnormalities → ventricular arrhythmia and/or regional fibrosis → LV or biventricular dilation and systolic dysfunction → advanced HF, ICD therapies, VAD/transplantation, or death. Progression is variable and not inevitably linear.

Reverse remodeling can occur with guideline-directed HF therapy, but genetic myocardial substrate and scar may persist. There is no reliable spontaneous-remission rate for DCM1BB. Critical opportunities are presymptomatic cascade detection, avoidance of high-intensity exercise, treatment at the first evidence of ventricular dysfunction, and timely sudden-death risk assessment.

9. Inheritance and population

Inheritance

Both autosomal-dominant, incompletely penetrant and autosomal-recessive/biallelic severe patterns occur across DSG2 cardiomyopathy. Monoallelic missense or truncating variants may act dominantly, sometimes with oligogenic or environmental modifiers. Homozygous or compound heterozygous loss-of-function variants can produce early, severe biventricular disease. (shiba2021phenotypicrecapitulationand pages 2-3, pinci2026integrativegenomicand pages 1-6, zhang2024hyperactivationofatf4tgfβ1 pages 1-2, sumida2024fourcardiomyopathypatients pages 1-2)

Penetrance is age-dependent and variable. A recent integrated DSG2 cohort estimated approximately 42% penetrance among genotype-positive relatives; in 95 carriers, 13% had major ventricular arrhythmias, 3% underwent transplantation, and 3% died. These 2026 data are informative but postdate the user’s preferred 2023–2024 window and concern broader DSG2-ACM rather than DCM1BB alone. (pinci2026integrativegenomicand pages 1-6)

No convincing genetic anticipation is established. Germline mosaicism is biologically possible but not a defining feature. Founder effects may occur for individual variants, but no universal DCM1BB founder population is known. Consanguinity increases the likelihood of biallelic disease. Carrier frequency is variant- and ancestry-specific and cannot be inferred from DCM prevalence.

Epidemiology

Subtype-specific incidence and prevalence are unknown. Broader modern DCM prevalence is approximately 1 in 220–250 (0.4–0.45%), with older incidence estimates around 6–8 per 100,000 person-years; these numbers must not be assigned directly to DCM1BB. In a UK Biobank CMR analysis, DCM prevalence was 1 in 220, 0.45% (95% CI 0.39–0.53%). Broader ACM prevalence is estimated at 1:2,000–1:5,000. (newman2024dilatedcardiomyopathya pages 1-2, vencato2024animalmodelsand pages 1-2)

No reliable DCM1BB sex ratio, age distribution, or geographic distribution exists. Male sex often increases penetrance and arrhythmic expression in desmosomal ACM generally, but a DSG2-specific quantitative estimate was not verified here.

10. Diagnostics

Clinical evaluation

Diagnosis requires confirmation of the cardiomyopathy phenotype and exclusion of sufficient acquired causes. Recommended assessment includes:

Three-generation pedigree, personal history, exercise exposure, pregnancy, alcohol, cardiotoxic drugs, infection/myocarditis, and neuromuscular/cutaneous findings.
Physical examination and 12-lead ECG.
Ambulatory ECG/Holter for premature ventricular complexes, nonsustained/sustained VT, and conduction disease.
Transthoracic echocardiography for LV/RV dimensions, ejection fraction, strain, valvular regurgitation, and hemodynamics.
CMR for chamber phenotype, function, edema, and late-gadolinium-enhancement fibrosis; contemporary reviews regard CMR as the reference noninvasive modality for scar and tissue phenotyping. (gasior2024advancesincardiac pages 1-2)
Laboratory testing: BNP/NT-proBNP, high-sensitivity troponin, complete blood count, electrolytes, renal/liver function, thyroid studies, iron indices, creatine kinase, and directed infectious/autoimmune/metabolic tests.
Exercise testing when clinically safe for functional and arrhythmic assessment, not to provoke maximal athletic exposure.
Endomyocardial biopsy only when myocarditis, infiltrative/storage disease, or another biopsy-actionable diagnosis is suspected; it is not routinely required for genetic DCM. (grasso2024thenew2023 pages 1-2)

Genetic testing

A cardiomyopathy/arrhythmogenic-cardiomyopathy NGS panel containing DSG2 and other robust genes is preferred, with deletion/duplication analysis. Testing should include genes for overlapping DCM/ACM phenotypes—at minimum major desmosomal genes and robust DCM genes—and must be coupled to genetic counseling. Genetic testing is considered a first-tier DCM investigation, but indiscriminately larger panels increase VUS burden more than diagnostic yield. (grasso2024thenew2023 pages 1-2, stroeks2023diagnosticandprognostic pages 1-2)

Single-gene DSG2 testing is reasonable when a known familial variant exists. WES/WGS is useful after a negative high-quality panel, in severe early-onset disease, consanguinity, suspected oligogenic disease, or when CNV/noncoding analysis is needed. WGS may detect structural and deep intronic variants but does not eliminate interpretation uncertainty. CMA can detect larger deletions but is not first-line for an isolated sequence-level disorder. Karyotyping, FISH, mitochondrial sequencing, and repeat-expansion testing are not routine unless another syndrome is suspected.

RNA sequencing from blood may be uninformative if DSG2 is poorly expressed; myocardial or iPSC RNA studies can clarify splicing but remain specialized. Proteomics, metabolomics, epigenomics, and liquid biopsy have no validated diagnostic role.

Differential diagnosis

Exclude ischemic cardiomyopathy; myocarditis/sarcoidosis; alcohol or stimulant toxicity; anthracycline/trastuzumab injury; peripartum cardiomyopathy; tachycardia-mediated cardiomyopathy; valvular/hypertensive disease; congenital shunts; endocrine, iron, nutritional, mitochondrial, and neuromuscular disease; and other genetic cardiomyopathies such as TTN, LMNA, FLNC, RBM20, DSP, PKP2, DSC2, BAG3, DES, and PLN disease.

Family screening should combine cascade genetic testing for a confirmed P/LP familial variant with serial ECG, ambulatory monitoring, echocardiography, and selective CMR. A negative targeted familial test generally releases a relative from genotype-specific surveillance, whereas a VUS should not drive predictive testing.

11. Outcomes and prognosis

There are no robust 5- or 10-year survival estimates specific to DCM1BB. Outcomes range from lifelong phenotype negativity to sudden arrhythmic death or end-stage biventricular failure. Adverse features plausibly include biallelic/multilocus disease, early onset, ventricular arrhythmia, extensive CMR fibrosis, reduced LV/RV ejection fraction, recurrent myocarditis-like injury, high exercise exposure, and progressive HF. (pinci2026integrativegenomicand pages 1-6, zhang2024hyperactivationofatf4tgfβ1 pages 1-2, vencato2024animalmodelsand pages 1-2)

For broader nonischemic DCM, approximately 50% experienced life-threatening arrhythmia, unplanned cardiovascular hospitalization, or cardiovascular death over 12 years in one contemporary long-term dataset; 17% experienced death, transplantation, or VAD implantation over eight years in another. These are context estimates, not DCM1BB-specific. Pathogenic/likely pathogenic variants generally confer worse prognosis than gene-elusive DCM. (newman2024dilatedcardiomyopathya pages 1-2)

Morbidity includes exercise limitation, recurrent arrhythmia, ICD implantation and shocks, hospitalization, thromboembolism, progressive HF, VAD, and transplantation. Recovery of ejection fraction is possible with treatment, but treatment withdrawal is generally inappropriate in genetic DCM because relapse risk persists.

12. Treatment and current applications

Current standard care

There is no approved DSG2-corrective therapy. Management follows DCM/HFrEF and ACM principles:

ARNI sacubitril/valsartan or an ACE inhibitor/ARB; NCIT concept: angiotensin-receptor/neprilysin inhibitor or renin–angiotensin-system inhibitor.
Evidence-based beta-blocker.
Mineralocorticoid-receptor antagonist such as spironolactone or eplerenone.
SGLT2 inhibitor such as dapagliflozin or empagliflozin.
Loop diuretic for congestion.
Anticoagulation for atrial fibrillation, intracardiac thrombus, or another standard indication—not solely for DSG2 status.
Antiarrhythmics and catheter ablation for recurrent ventricular arrhythmia, recognizing recurrence can occur as disease progresses.
ICD for secondary prevention and selected primary prevention based on ventricular function, scar, arrhythmic history, syncope, and overall genotype/phenotype risk.
CRT for standard electrical/mechanical dyssynchrony indications.
VAD and heart transplantation for refractory advanced HF.

No CPIC or PharmGKB genotype-guided dosing recommendation specific to DSG2 was identified. Treatment should be phenotype- and risk-guided rather than based on a DSG2 VUS.

Lifestyle and rehabilitation

Competitive and high-intensity endurance exercise should generally be avoided in affected individuals and discussed cautiously in genotype-positive relatives. Stable patients may undertake individualized low-to-moderate activity through cardiology/cardiac-rehabilitation supervision; complete inactivity has its own harms. Sodium/fluid advice, vaccination, weight control, smoking cessation, and psychosocial support follow HF standards. (gasior2024advancesincardiac pages 1-2, vencato2024animalmodelsand pages 1-2)

Experimental therapy

Human DSG2-deficient iPSC-CMs provide proof of concept for HDR correction and AAV-mediated gene replacement, with restoration of desmosomes, electrophysiology, tissue strength, and contractile force. These experiments support precision-therapy development but do not establish clinical feasibility, dosing, durability, immunogenicity, or safety. (shiba2021phenotypicrecapitulationand pages 10-11, shiba2021phenotypicrecapitulationand pages 2-3, shiba2021phenotypicrecapitulationand pages 1-1)

Potential preclinical targets include PERK–ATF4–TGF-β1, NF-κB/CCR2 macrophage signaling, Wnt/Hippo balance, connexin-43, and fibrosis pathways. The 2024 studies make ATF4/TGF-β1 and NF-κB/CCR2 especially compelling, but systemic immune or ER-stress inhibition could have substantial off-target effects. (zhang2024hyperactivationofatf4tgfβ1 pages 1-2, chelko2024nfĸbsignalingdrives pages 1-2)

No DSG2-specific interventional clinical trial was identified in the trial search. Current gene-therapy trials in ACM target PKP2, not DSG2; these demonstrate field momentum but should not be represented as DCM1BB treatments. Relevant field studies include NCT06109181 and NCT05885412 (PKP2 gene replacement), NCT05569356 (observational ACM study), and NCT06275893 (anti-inflammatory intervention). ClinicalTrials.gov URLs follow the form https://clinicaltrials.gov/study/NCT06109181.

13. Prevention

Primary prevention

The germline variant cannot currently be prevented after conception. Reproductive options include preconception genetic counseling, partner testing when recessive disease is possible, preimplantation genetic testing for a known familial P/LP variant, and prenatal diagnosis after informed counseling. Population or newborn screening for DSG2 is not currently recommended.

Secondary prevention

Cascade testing and longitudinal phenotyping are the most important preventive measures. Early ECG, Holter, echocardiography, and CMR can identify electrical disease, scar, or ventricular dysfunction before symptoms. Surveillance intervals should be individualized by age, genotype, family history, exercise, and prior findings.

Tertiary prevention

Guideline-directed HF therapy, exercise restriction, ICD selection, arrhythmia treatment, vaccination, management of pregnancy risk, and timely referral for advanced HF reduce complications. There is no disease-specific vaccine or prophylactic medication. Genetic counseling should explain incomplete penetrance, variable expressivity, uncertain significance of many variants, and the possibility of biallelic or multilocus inheritance.

14. Other species and natural disease

Orthologous Dsg2 is conserved across vertebrates, reflecting the conserved requirement for desmosomal adhesion in mechanically stressed tissues. Naturally occurring dilated or arrhythmogenic cardiomyopathy occurs in dogs and other mammals, but a verified naturally occurring DSG2-defined veterinary counterpart with breed/VBO identifier was not established from the retrieved evidence. No zoonotic transmission is possible because this is an inherited, noninfectious disorder.

Suggested taxa for experimental comparative annotation include Homo sapiens, NCBI Taxon 9606 and Mus musculus, NCBI Taxon 10090. Orthologue-specific NCBI Gene identifiers should be retrieved directly from NCBI Gene before production ingestion rather than inferred here.

15. Model organisms and experimental systems

Mouse models

Available models include homozygous and heterozygous knock-in mutants, cardiac-specific knockout, and variant-overexpression models. They reproduce combinations of cardiomyocyte death, inflammation, fibrosis, ventricular dilation, reduced function, conduction delay, ventricular arrhythmia, and premature death. (shiba2021phenotypicrecapitulationand pages 1-2, zhang2024hyperactivationofatf4tgfβ1 pages 1-2, chelko2024nfĸbsignalingdrives pages 1-2)

The Dsg2F536C/F536C knock-in model reproduces the human F531C family’s cardiac enlargement, biventricular fibrosis, and dysfunction and enabled transcriptomic and mass-spectrometric discovery of PERK–ATF4–TGF-β1 signaling. (zhang2024hyperactivationofatf4tgfβ1 pages 1-2)

The Dsg2mut/mut model supports single-cell resolution of cardiomyocyte–macrophage–fibroblast interactions. Blocking cardiomyocyte NF-κB or CCR2-positive-cell recruitment attenuated injury, demonstrating causal immune participation. (chelko2024nfĸbsignalingdrives pages 1-2)

Heterozygous Dsg2 mice have limited spontaneous phenotype but develop RV dilation, dysfunction, activation delay, and inducible arrhythmia after endurance training. This model is useful for incomplete penetrance and gene–environment studies. (vencato2024animalmodelsand pages 1-2)

Limitations include species differences in cardiac loading, electrophysiology, lifespan, allele dosage, and adipose remodeling. Complete DSG2 deficiency can have different developmental consequences in mice and humans; therefore, mouse rescue cannot be assumed to predict clinical efficacy. (shiba2021phenotypicrecapitulationand pages 9-10)

Human cellular models

Patient-derived p.Arg119Ter iPSC-CMs and isogenic HDR-corrected controls are the most disease-specific platform. They reproduce abnormal excitation, desmosomal ultrastructure, reduced desmocollin-2, tissue fragility, and weak contraction, while correction or AAV replacement rescues key phenotypes. (shiba2021phenotypicrecapitulationand pages 10-11, shiba2021phenotypicrecapitulationand pages 4-5, shiba2021phenotypicrecapitulationand pages 1-1)

Limitations include fetal-like iPSC-CM maturation, absent systemic immunity and neurohormonal loading, variable cell composition, and short experimental duration. Three-dimensional tissues, electrical/mechanical conditioning, multicellular organoids, and isogenic controls improve relevance.

Key 2023–2024 developments and authoritative interpretation

December 20, 2024—p.Arg119Ter human cohort: Four carriers among 808 nonischemic-cardiomyopathy patients demonstrated broad phenotypic expression and ultrastructural desmosomal disruption. The authors concluded that the allele may be a latent exacerbating factor rather than uniformly sufficient monoallelic disease. DOI: https://doi.org/10.1038/s41439-024-00304-w. Their abstract reports “pale and fragmented desmosomes and widened gaps between intercalated discs.” (sumida2024fourcardiomyopathypatients pages 1-2)
September 2024—variant-specific fibrosis pathway: F531C misfolding linked DSG2 to BiP/PERK/ATF4/TGF-β1 and paracrine fibroblast activation. DOI: https://doi.org/10.1186/s12916-024-03593-8. (zhang2024hyperactivationofatf4tgfβ1 pages 1-2)
April 2, 2024—single-cell immune mechanism: Cardiomyocyte NF-κB and recruited CCR2-positive macrophages were shown to drive injury and arrhythmia in Dsg2 mice. DOI: https://doi.org/10.1172/JCI172014. (chelko2024nfĸbsignalingdrives pages 1-2)
June 5, 2024—model synthesis: Contemporary review emphasized Wnt/β-catenin inhibition, Hippo/TGF-β activation, intercalated-disc biology, and exercise as an ACM accelerator. DOI: https://doi.org/10.3390/ijms25116208. (vencato2024animalmodelsand pages 1-2)
2023–2024 clinical implementation: ESC-informed practice now integrates deep phenotype, CMR, pedigree, and genetic testing, rather than using morphology or genotype alone. Large uncurated panels add VUSs with little incremental diagnostic yield. DOI: https://doi.org/10.1038/s41431-023-01384-y; https://doi.org/10.1093/eurheartjsupp/suae002; https://doi.org/10.3390/jcm13237166. (grasso2024thenew2023 pages 1-2, stroeks2023diagnosticandprognostic pages 1-2, gasior2024advancesincardiac pages 1-2)

Evidence-quality assessment and major gaps

Strongest disease-specific evidence: human genotype–phenotype observations, myocardial pathology, p.Arg119Ter iPSC-CM disease reproduction, and isogenic correction. Strong mechanistic but preclinical evidence: Dsg2 knock-in/knockout mice, single-cell immune profiling, ER-stress signaling, and exercise loading. Broader extrapolation: prevalence, exercise-risk magnitude, HF outcomes, and treatment response are derived largely from general DCM or ACM.

Critical gaps are: no population prevalence for DCM1BB; no prospective DSG2-only natural-history cohort in the 2023–2024 literature; uncertain pathogenic sufficiency of many monoallelic variants; no validated DSG2-specific biomarker; sparse sex- and ancestry-stratified penetrance; no subtype-specific quality-of-life data; no approved molecular therapy; and no DSG2-targeted interventional trial. Consequently, knowledge-base entries should encode evidence provenance and avoid transferring generic ACM frequencies or mouse pathways to every DSG2 variant without qualification.

References

(OpenTargets Search: Dilated cardiomyopathy 1BB): Open Targets Query (Dilated cardiomyopathy 1BB, 1 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(shiba2021phenotypicrecapitulationand pages 2-3): Mikio Shiba, Shuichiro Higo, Takumi Kondo, Junjun Li, Li Liu, Yoshihiko Ikeda, Yasuaki Kohama, Satoshi Kameda, Tomoka Tabata, Hiroyuki Inoue, Satoki Nakamura, Maki Takeda, Emiko Ito, Seiji Takashima, Shigeru Miyagawa, Yoshiki Sawa, Shungo Hikoso, and Yasushi Sakata. Phenotypic recapitulation and correction of desmoglein-2-deficient cardiomyopathy using human-induced pluripotent stem cell-derived cardiomyocytes. Human Molecular Genetics, 30:1384-1397, May 2021. URL: https://doi.org/10.1093/hmg/ddab127, doi:10.1093/hmg/ddab127. This article has 41 citations and is from a domain leading peer-reviewed journal.
(pinci2026integrativegenomicand pages 1-6): Serena Pinci, Rudy Celeghin, Marika Martini, Monica De Gaspari, Maria Bueno Marinas, Giulia Tosato, Francesca Dalla Zanna, Marco Cason, Ilaria Rigato, Gaetano Thiene, Stefania Rizzo, Domenico Corrado, Cristina Basso, Barbara Bauce, and Kalliopi Pilichou. Integrative genomic and literature assessment of desmoglein 2-related arrhythmogenic cardiomyopathy with italian cohort validation. Communications Medicine, Feb 2026. URL: https://doi.org/10.1038/s43856-026-01416-w, doi:10.1038/s43856-026-01416-w. This article has 1 citations and is from a peer-reviewed journal.
(zhang2024hyperactivationofatf4tgfβ1 pages 1-2): Baowei Zhang, Yizhang Wu, Chunjiang Zhou, Jiaxi Xie, Youming Zhang, Xingbo Yang, Jing Xiao, Dao Wu Wang, Congjia Shan, Xiujuan Zhou, Yaozu Xiang, and Bing Yang. Hyperactivation of atf4/tgf-β1 signaling contributes to the progressive cardiac fibrosis in arrhythmogenic cardiomyopathy caused by dsg2 variant. BMC Medicine, Sep 2024. URL: https://doi.org/10.1186/s12916-024-03593-8, doi:10.1186/s12916-024-03593-8. This article has 18 citations and is from a domain leading peer-reviewed journal.
(sumida2024fourcardiomyopathypatients pages 1-2): Takuya Sumida, Shou Ogawa, Shuichiro Higo, Yuki Kuramoto, Ryo Eto, Yoshihiko Ikeda, Congcong Sun, Junjun Li, Li Liu, Tomoka Tabata, Yoshihiro Asano, Mikio Shiba, Yasuhiro Akazawa, Daisuke Nakamura, Takafumi Oka, Tomohito Ohtani, and Yasushi Sakata. Four cardiomyopathy patients with a heterozygous dsg2 p.arg119ter variant. Human Genome Variation, Dec 2024. URL: https://doi.org/10.1038/s41439-024-00304-w, doi:10.1038/s41439-024-00304-w. This article has 2 citations.
(shiba2021phenotypicrecapitulationand pages 1-1): Mikio Shiba, Shuichiro Higo, Takumi Kondo, Junjun Li, Li Liu, Yoshihiko Ikeda, Yasuaki Kohama, Satoshi Kameda, Tomoka Tabata, Hiroyuki Inoue, Satoki Nakamura, Maki Takeda, Emiko Ito, Seiji Takashima, Shigeru Miyagawa, Yoshiki Sawa, Shungo Hikoso, and Yasushi Sakata. Phenotypic recapitulation and correction of desmoglein-2-deficient cardiomyopathy using human-induced pluripotent stem cell-derived cardiomyocytes. Human Molecular Genetics, 30:1384-1397, May 2021. URL: https://doi.org/10.1093/hmg/ddab127, doi:10.1093/hmg/ddab127. This article has 41 citations and is from a domain leading peer-reviewed journal.
(shiba2021phenotypicrecapitulationand pages 10-11): Mikio Shiba, Shuichiro Higo, Takumi Kondo, Junjun Li, Li Liu, Yoshihiko Ikeda, Yasuaki Kohama, Satoshi Kameda, Tomoka Tabata, Hiroyuki Inoue, Satoki Nakamura, Maki Takeda, Emiko Ito, Seiji Takashima, Shigeru Miyagawa, Yoshiki Sawa, Shungo Hikoso, and Yasushi Sakata. Phenotypic recapitulation and correction of desmoglein-2-deficient cardiomyopathy using human-induced pluripotent stem cell-derived cardiomyocytes. Human Molecular Genetics, 30:1384-1397, May 2021. URL: https://doi.org/10.1093/hmg/ddab127, doi:10.1093/hmg/ddab127. This article has 41 citations and is from a domain leading peer-reviewed journal.
(chelko2024nfĸbsignalingdrives pages 1-2): Stephen P. Chelko, Vinay R. Penna, Morgan Engel, Emily A. Shiel, Ann M. Centner, Waleed Farra, Elisa N. Cannon, Maicon Landim-Vieira, Niccole Schaible, Kory Lavine, and Jeffrey E. Saffitz. Nfĸb signaling drives myocardial injury via ccr2+ macrophages in a preclinical model of arrhythmogenic cardiomyopathy. The Journal of Clinical Investigation, Jul 2024. URL: https://doi.org/10.1172/jci183441, doi:10.1172/jci183441. This article has 48 citations.
(stroeks2023diagnosticandprognostic pages 1-2): Sophie L. V. M. Stroeks, Debby Hellebrekers, Godelieve R. F. Claes, Ingrid P. C. Krapels, Michiel H. T. M. Henkens, Maurits Sikking, Els K. Vanhoutte, Apollonia Helderman-van den Enden, Han G. Brunner, Arthur van den Wijngaard, and Job A. J. Verdonschot. Diagnostic and prognostic relevance of using large gene panels in the genetic testing of patients with dilated cardiomyopathy. European Journal of Human Genetics, 31:776-783, May 2023. URL: https://doi.org/10.1038/s41431-023-01384-y, doi:10.1038/s41431-023-01384-y. This article has 10 citations and is from a domain leading peer-reviewed journal.
(grasso2024thenew2023 pages 1-2): Maurizia Grasso, Davide Bondavalli, Viviana Vilardo, Claudia Cavaliere, Ilaria Gatti, Alessandro Di Toro, Lorenzo Giuliani, Mario Urtis, Michela Ferrari, Barbara Cattadori, Alessandra Serio, Carlo Pellegrini, and Eloisa Arbustini. The new 2023 esc guidelines for the management of cardiomyopathies: a guiding path for cardiologist decisions. European Heart Journal Supplements : Journal of the European Society of Cardiology, 26:i1-i5, Apr 2024. URL: https://doi.org/10.1093/eurheartjsupp/suae002, doi:10.1093/eurheartjsupp/suae002. This article has 18 citations.
(gasior2024advancesincardiac pages 1-2): Tomasz Gasior. Advances in cardiac imaging and genetic testing for diagnosis and risk stratification in cardiomyopathies: 2024 update. Journal of Clinical Medicine, 13:7166, Nov 2024. URL: https://doi.org/10.3390/jcm13237166, doi:10.3390/jcm13237166. This article has 12 citations.
(vencato2024animalmodelsand pages 1-2): Sara Vencato, Chiara Romanato, Alessandra Rampazzo, and Martina Calore. Animal models and molecular pathogenesis of arrhythmogenic cardiomyopathy associated with pathogenic variants in intercalated disc genes. Jun 2024. URL: https://doi.org/10.3390/ijms25116208, doi:10.3390/ijms25116208. This article has 10 citations.
(newman2024dilatedcardiomyopathya pages 1-2): Noah A. Newman and Michael A. Burke. Dilated cardiomyopathy: a genetic journey from past to future. International Journal of Molecular Sciences, 25:11460, Oct 2024. URL: https://doi.org/10.3390/ijms252111460, doi:10.3390/ijms252111460. This article has 28 citations.
(pinci2026integrativegenomicand pages 26-31): Serena Pinci, Rudy Celeghin, Marika Martini, Monica De Gaspari, Maria Bueno Marinas, Giulia Tosato, Francesca Dalla Zanna, Marco Cason, Ilaria Rigato, Gaetano Thiene, Stefania Rizzo, Domenico Corrado, Cristina Basso, Barbara Bauce, and Kalliopi Pilichou. Integrative genomic and literature assessment of desmoglein 2-related arrhythmogenic cardiomyopathy with italian cohort validation. Communications Medicine, Feb 2026. URL: https://doi.org/10.1038/s43856-026-01416-w, doi:10.1038/s43856-026-01416-w. This article has 1 citations and is from a peer-reviewed journal.
(shiba2021phenotypicrecapitulationand pages 9-10): Mikio Shiba, Shuichiro Higo, Takumi Kondo, Junjun Li, Li Liu, Yoshihiko Ikeda, Yasuaki Kohama, Satoshi Kameda, Tomoka Tabata, Hiroyuki Inoue, Satoki Nakamura, Maki Takeda, Emiko Ito, Seiji Takashima, Shigeru Miyagawa, Yoshiki Sawa, Shungo Hikoso, and Yasushi Sakata. Phenotypic recapitulation and correction of desmoglein-2-deficient cardiomyopathy using human-induced pluripotent stem cell-derived cardiomyocytes. Human Molecular Genetics, 30:1384-1397, May 2021. URL: https://doi.org/10.1093/hmg/ddab127, doi:10.1093/hmg/ddab127. This article has 41 citations and is from a domain leading peer-reviewed journal.
(shiba2021phenotypicrecapitulationand pages 1-2): Mikio Shiba, Shuichiro Higo, Takumi Kondo, Junjun Li, Li Liu, Yoshihiko Ikeda, Yasuaki Kohama, Satoshi Kameda, Tomoka Tabata, Hiroyuki Inoue, Satoki Nakamura, Maki Takeda, Emiko Ito, Seiji Takashima, Shigeru Miyagawa, Yoshiki Sawa, Shungo Hikoso, and Yasushi Sakata. Phenotypic recapitulation and correction of desmoglein-2-deficient cardiomyopathy using human-induced pluripotent stem cell-derived cardiomyocytes. Human Molecular Genetics, 30:1384-1397, May 2021. URL: https://doi.org/10.1093/hmg/ddab127, doi:10.1093/hmg/ddab127. This article has 41 citations and is from a domain leading peer-reviewed journal.
(shiba2021phenotypicrecapitulationand pages 4-5): Mikio Shiba, Shuichiro Higo, Takumi Kondo, Junjun Li, Li Liu, Yoshihiko Ikeda, Yasuaki Kohama, Satoshi Kameda, Tomoka Tabata, Hiroyuki Inoue, Satoki Nakamura, Maki Takeda, Emiko Ito, Seiji Takashima, Shigeru Miyagawa, Yoshiki Sawa, Shungo Hikoso, and Yasushi Sakata. Phenotypic recapitulation and correction of desmoglein-2-deficient cardiomyopathy using human-induced pluripotent stem cell-derived cardiomyocytes. Human Molecular Genetics, 30:1384-1397, May 2021. URL: https://doi.org/10.1093/hmg/ddab127, doi:10.1093/hmg/ddab127. This article has 41 citations and is from a domain leading peer-reviewed journal.

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Unresolved (possible confabulation)	0
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References weighed for topical relevance	11
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Dilated Cardiomyopathy 1BB (DSG2-associated cardiomyopathy): comprehensive disease-characteristics report

Executive summary and scope

1. Disease information

Definition

Identifiers and synonyms

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

Causal factors

Genetic risk factors and modifiers

Environmental and lifestyle risk factors

Protective factors

3. Phenotypes

4. Genetic and molecular information

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5. Environmental information

6. Mechanism and pathophysiology

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2024 mechanistic advances

7. Anatomical structures affected

8. Temporal development

9. Inheritance and population

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10. Diagnostics

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11. Outcomes and prognosis

12. Treatment and current applications

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