| Domain | HCM2-specific fact | Suggested ontology IDs/terms | Evidence/qualification |
|---|---|---|---|
| Identity | Historical disease entity is **Hypertrophic cardiomyopathy 2 (HCM2)**, a **TNNT2-related familial hypertrophic cardiomyopathy** subtype; use disease-level resources with caution because many current sources collapse numbered subtypes into generic HCM. | **OMIM: 115195** (if using historical subtype mapping); **TNNT2 / HGNC:11949**; **MONDO caveat:** use generic **hypertrophic cardiomyopathy MONDO:0005045** when subtype MONDO is not confidently established | TNNT2 is an established HCM target/disease association; numbering/scope caveat because recent resources emphasize gene-defined sarcomeric HCM rather than historic subtype labels (pqac-00000000) |
| Synonyms | Suggested labels: **TNNT2-related hypertrophic cardiomyopathy**, **cardiac troponin T-associated hypertrophic cardiomyopathy**, **familial hypertrophic cardiomyopathy due to TNNT2** | MeSH/ICD not confidently subtype-specific here; retain free-text synonyms | Modern literature usually discusses TNNT2-positive HCM rather than “HCM2” as a primary label (pqac-00000000, pqac-00000004) |
| Etiology | Primary cause is **heterozygous germline pathogenic/likely pathogenic variants in TNNT2**, encoding cardiac troponin T, a thin-filament sarcomeric protein | **TNNT2 / HGNC:11949**; sarcomere/thin filament terms as annotations | Supported by disease-target evidence and TNNT2-specific primary studies/models (pqac-00000000, pqac-00000001, pqac-00000002, pqac-00000003) |
| Inheritance | Typically **autosomal dominant** with **age-dependent, incomplete penetrance** and variable expressivity | HPO inheritance term may be added locally if needed; no ID asserted here | General genetic HCM evidence; applies to TNNT2-positive families, with gene-specific penetrance estimates available (pqac-00000002, pqac-00000004) |
| Penetrance / natural history | Meta-analysis estimate for **TNNT2 penetrance ~60%** in nonproband relatives identified by cascade screening; mean age at HCM diagnosis ~**38 years**; phenotypic conversion across sarcomeric HCM about **15% over ~8 years** from subclinical state | Phenotype conversion / age-dependent penetrance annotations | Best recent quantitative estimate; this is family/clinical-context penetrance, not incidental population penetrance (pqac-00000004) |
| Variant classes | Reported pathogenic TNNT2 variants in HCM include **missense** and **small in-frame deletion** variants; notable research variants include **R92Q**, **I79N**, **Δ160E** | Sequence Ontology terms can be added locally (missense_variant, inframe_deletion) | Variant examples are from mechanistic/model papers; not an exhaustive clinical variant catalog (pqac-00000001, pqac-00000002, pqac-00000003) |
| Core phenotype | Unexplained **left ventricular hypertrophy** with familial sarcomeric cardiomyopathy features | **HP:0001712 Left ventricular hypertrophy** | TNNT2-specific and general HCM-defining feature; subtype-specific frequency not precisely quantified in retrieved evidence (pqac-00000003, pqac-00000014) |
| Arrhythmic phenotype | TNNT2 variants can confer **high arrhythmic risk and sudden death risk**, sometimes **despite mild hypertrophy** | **HP:0001645 Arrhythmia**; **HP:0001680 Ventricular arrhythmia**; **HP:0001644 Syncope**; **HP:0001699 Sudden cardiac death** | Strongly emphasized for TNNT2 variants, especially I79N and thin-filament HCM literature (pqac-00000002) |
| Diastolic/relaxation phenotype | Relaxation impairment and diastolic dysfunction are prominent early phenotypes linked to increased myofilament Ca2+ sensitivity | **HP:0005157 Abnormal left ventricular diastolic function** | Directly shown in TNNT2 Δ160E and zebrafish TNNT2 models (pqac-00000001, pqac-00000006) |
| Cellular hypertrophy | Mutant cardiomyocytes show increased cell size and hypertrophic signaling | **HP:0001639 Cardiomyocyte hypertrophy** if locally mapped; **HP:0000822?** not asserted if uncertain | Derived mainly from hESC/iPSC cardiomyocyte models; keep as experimental phenotype annotation (pqac-00000001, pqac-00000003) |
| Sarcomere disarray | TNNT2-HCM models show **myofilament/myofibrillar disarray** | **HP:0005179 Myocardial fiber disarray** (suggested if local ontology supports exact term) | Strong experimental support in TNNT2 R92Q and I79N models (pqac-00000002, pqac-00000003) |
| Biomarker phenotype | Natriuretic peptide and injury biomarker elevation may occur in HCM; TNNT2 I79N model showed **NPPA/NPPB upregulation** | **HP:0031185 Elevated circulating NT-proBNP level** (general-HCM extrapolation); transcript markers **NPPA/NPPB** | Direct TNNT2 evidence is transcriptomic/model-based; circulating biomarker use is broader HCM extrapolation (pqac-00000002, pqac-00000009, pqac-00000015) |
| Mechanism: primary biophysical defect | Upstream mechanism is **increased myofilament Ca2+ sensitivity** and **slower Ca2+ dissociation/off-rate** from thin filament regulation | **GO:0051592 response to calcium ion**; **GO:0006936 muscle contraction**; **GO:0030049 muscle filament sliding** | Core TNNT2 mechanism shown for I79N, Δ160E, and R92Q models (pqac-00000001, pqac-00000002, pqac-00000003) |
| Mechanism: calcium handling | Mutations drive **prolonged calcium decay**, intracellular Ca2+ retention/buffering abnormalities, and impaired relaxation | **GO:0051480 regulation of cytosolic calcium ion concentration**; **GO:1903779 regulation of cardiac conduction?** not asserted if uncertain | Strong TNNT2-specific model evidence (pqac-00000001, pqac-00000002, pqac-00000006) |
| Mechanism: hypertrophic signaling | Downstream signaling includes **NFATc1 nuclear translocation** and **increased CaMKIIδ / phospholamban phosphorylation** | **GO:0006468 protein phosphorylation**; **GO:0007205 protein kinase C-activating GPCR signaling?** not asserted; **GO:0006950 response to stress** if needed | Direct TNNT2 Δ160E evidence; useful for pathway annotation but not yet routine clinical biomarker use (pqac-00000001) |
| Mechanism: electrophysiology | Ca2+ dysregulation promotes **beat-to-beat instability**, **action-potential triangulation**, and **alternans**, creating an arrhythmic substrate/trigger | **GO:0086001 cardiac muscle cell action potential**; **GO:1903779 regulation of cardiac conduction** | Strong TNNT2 I79N hiPSC-CM evidence (pqac-00000002) |
| Mechanism: energetics / oxidative stress | Recent HCM work supports a broader sarcomeric-HCM mechanism in which increased Ca2+ sensitivity causes **bioenergetic mismatch**, **mitochondrial ROS**, spontaneous Ca2+ release, and arrhythmias | **GO:0006979 response to oxidative stress**; **GO:0042775 mitochondrial ATP synthesis coupled electron transport** | General-HCM extrapolation from HCM mouse models including TNNT2-I79N; promising but partly preprint-stage for 2024 evidence (pqac-00000007) |
| Tissue remodeling | Fibrosis/ECM-remodeling programs are downstream disease features; TNNT2 I79N transcriptomics showed ECM-remodeling signatures | **GO:0030198 extracellular matrix organization**; **GO:0061448 connective tissue development?** not asserted; **HP:0005680 Myocardial fibrosis** (suggested) | Direct transcriptomic/model support; clinical fibrosis imaging is often inferred from general HCM practice (pqac-00000002, pqac-00000010) |
| Cell types | Primary affected cell type is **cardiomyocyte**; fibroblasts and endothelial/immune compartments are likely secondary participants in remodeling/fibrosis | **CL:0002494 cardiomyocyte**; **CL:0000057 fibroblast**; endothelial cell term may be added locally if needed | Cardiomyocyte involvement is direct; fibroblast/endothelial participation is mainly general-HCM extrapolation from fibrosis literature (pqac-00000001, pqac-00000002, pqac-00000007) |
| Anatomy | Primary organ/site is **heart**, especially **left ventricular myocardium**; obstruction may involve **left ventricular outflow tract** in obstructive phenotypes | **UBERON:0000948 heart**; **UBERON:0002084 myocardium**; **UBERON:0002080 cardiac ventricle**; LVOT term add locally if curated | HCM-anatomy statements are partly generic HCM criteria because TNNT2-specific anatomy is not uniquely distinct (pqac-00000003, pqac-00000010, pqac-00000014) |
| Subcellular localization | Disease-relevant compartment is the **sarcomeric thin filament / myofilament complex** | GO cellular-component terms can be added locally, e.g. sarcomere/thin filament if curated from external ontology | Strong mechanistic fit, but specific GO CC IDs were not verified in retrieved context, so not asserted numerically |
| Diagnostics: clinical definition | HCM diagnosis in adults generally requires **unexplained LV wall thickness ≥15 mm**; **≥13 mm** in first-degree relatives can support diagnosis | Diagnostic threshold annotation; **HP:0001712** | **General-HCM extrapolation** from current diagnostic practice, applied to TNNT2-HCM when subtype-specific criteria are absent (pqac-00000014) |
| Diagnostics: imaging | **Transthoracic echocardiography** is first-line; **CMR** is recommended for morphology clarification, apical disease, aneurysm/thrombus detection, and fibrosis/LGE assessment; provocation/exercise testing is used when obstruction is suspected but absent at rest | NCIT-style labels: Echocardiography, Cardiac MRI, Exercise Testing | Guideline-review level evidence, largely generic HCM but clinically applicable to TNNT2-HCM (pqac-00000010, pqac-00000014) |
| Diagnostics: genetic testing | Multigene cardiomyopathy testing including **TNNT2** is recommended to support diagnosis, cascade screening, and phenocopy distinction | **TNNT2 / HGNC:11949**; NCIT-style labels: Molecular Genetic Testing, Cascade Screening | Strongly supported in guideline reviews; phenotype-negative relatives are not genetically “diagnosed” without a known familial variant (pqac-00000010, pqac-00000014) |
| Differential diagnosis | Exclude **HCM phenocopies** and secondary hypertrophy causes: amyloidosis, Fabry disease, glycogen storage disease, mitochondrial disease, RASopathy, valvular/loading conditions, athlete’s heart | Use generic phenocopy/differential labels locally | Mostly general-HCM evidence, important because numbered HCM subtype labels can obscure phenocopies (pqac-00000010, pqac-00000014) |
| Epidemiology | HCM prevalence broadly is about **1 in 500** in classic estimates; TNNT2-specific disease is a minority sarcomeric subset; one review/meta-analysis found TNNT2 penetrance around 60% in family screening context | Population prevalence annotation; gene-specific subset flag | **General-HCM extrapolation** for overall prevalence; TNNT2-specific frequency not robustly quantified in retrieved evidence (pqac-00000002, pqac-00000004) |
| Prognosis | Prognosis is variable; TNNT2 variants are notable for **arrhythmia/sudden death risk** and in some variants for adverse remodeling or systolic dysfunction | Sudden-death risk annotation; heart-failure progression annotation | Subtype-specific risk is variant-dependent; avoid overgeneralizing all TNNT2 variants as uniformly high risk (pqac-00000001, pqac-00000002) |
| Prevention / family management | **Cascade screening** of relatives is central; exercise should generally be encouraged at mild-moderate intensity, while high-risk/high-intensity activity decisions are individualized; pregnancy medication review is needed and **mavacamten is contraindicated in pregnancy** | NCIT-style labels: Genetic Counseling, Family Screening, Exercise Counseling, Pregnancy Counseling | Mostly general-HCM guideline extrapolation but directly useful in TNNT2-HCM care pathways (pqac-00000010) |
| Standard pharmacotherapy | First-line symptomatic therapy for obstructive HCM: **beta-blocker**; alternatives include **verapamil/diltiazem**; **disopyramide** can be added in selected obstructive cases | NCIT-style labels: **Beta Adrenergic Receptor Blockade**, **Verapamil Therapy**, **Diltiazem Therapy**, **Disopyramide Therapy** | General-HCM treatment extrapolation; no TNNT2-specific drug-response biomarker established in retrieved evidence (pqac-00000013, pqac-00000014) |
| Targeted therapy | **Mavacamten** is a cardiac myosin inhibitor for symptomatic obstructive HCM; EXPLORER-HCM primary endpoint achieved in **37% vs 17%** placebo; VALOR-HCM reduced SRT eligibility to **17.9% vs 76.8%** after 16 weeks | NCIT-style labels: **Mavacamten Therapy**, **Cardiac Myosin Inhibitor Therapy** | High-quality general-HCM evidence; not TNNT2-specific, but directly relevant to sarcomeric obstructive HCM clinical implementation (pqac-00000009, pqac-00000011, pqac-00000015) |
| Emerging targeted therapy | **Aficamten** is a next-generation cardiac myosin inhibitor with shorter half-life and favorable trial results in obstructive HCM | NCIT-style labels: **Aficamten Therapy**, **Cardiac Myosin Inhibitor Therapy** | General-HCM extrapolation; regulatory/implementation status continues to evolve (pqac-00000009, pqac-00000012) |
| Procedures | If severe obstructive symptoms persist despite drug therapy, **septal reduction therapy** (surgical myectomy or alcohol septal ablation) is standard | NCIT-style labels: **Surgical Septal Myectomy**, **Alcohol Septal Ablation**, **Septal Reduction Therapy** | General-HCM standard of care; not gene-specific (pqac-00000011, pqac-00000013) |
| Device therapy | **ICD** used for primary/secondary prevention based on sudden-death risk stratification; one guideline approach recommends ICD for **5-year SCD risk ≥6%** and consideration at **4–6%** | NCIT-style labels: **Implantable Cardioverter Defibrillator** | General-HCM extrapolation from guideline review; TNNT2 genotype may inform concern but ICD decisions remain phenotype/risk-marker led (pqac-00000010) |
| Advanced HF therapy | End-stage disease may require advanced heart-failure care, including transplant in rare progressed cases | NCIT-style labels: **Heart Transplantation** | General-HCM extrapolation; relevant because some TNNT2 variants can progress to systolic dysfunction (pqac-00000001) |
| Experimental / mechanism-based therapy | **Calcium desensitization** is mechanistically attractive in TNNT2-HCM; **epigallocatechin-3-gallate** improved calcium decay/relaxation in Δ160E iPSC-CMs | CHEBI/compound IDs not asserted here; experimental therapy label locally | Preclinical only in retrieved evidence (pqac-00000001) |
| Models: human cellular | Human **hiPSC-CM** and **hESC-CM** TNNT2 models recapitulate hypertrophy, calcium dysregulation, disarray, and pro-arrhythmic phenotypes; examples: **Δ160E**, **I79N**, **R92Q** | Model labels: hiPSC-derived cardiomyocyte, hESC-derived cardiomyocyte, engineered heart tissue | Strong direct disease-model evidence and useful for assay/drug screening annotation (pqac-00000001, pqac-00000002, pqac-00000003) |
| Models: animal | **Mouse** TNNT2 models (e.g., I79N, R92Q) and **zebrafish tnnt2a RK94del** model reproduce Ca2+ dysregulation, remodeling, fibrosis, and arrhythmogenic traits | Organism labels locally; NCBI Taxon IDs not asserted to avoid invention | Strong comparative evidence; supports mechanism and therapeutic screening (pqac-00000006, pqac-00000007) |
| Data provenance | This entry should be populated primarily from **aggregated disease-level resources and primary literature**, not solely EHR-derived observations | Evidence-source annotation | Important because subtype identity is historical and modern datasets often aggregate into generic HCM (pqac-00000000, pqac-00000004) |


*Table: This compact table summarizes key facts for Hypertrophic Cardiomyopathy 2 as TNNT2-related HCM, with ontology suggestions and evidence qualifiers for direct knowledge-base ingestion. It distinguishes TNNT2-specific findings from general-HCM extrapolations and flags uncertain identifiers to avoid over-assertion.*