Dilated Cardiomyopathy 1II: Comprehensive Disease-Characteristics Report

Executive summary and evidence boundary

Dilated cardiomyopathy 1II (DCM1II) is a very rare, usually autosomal-dominant dilated-cardiomyopathy subtype associated with heterozygous variants in CRYAB/HSPB5, which encodes the small heat-shock protein αB-crystallin. The strongest disease-specific literature consists of a few patients or families—particularly those carrying p.Arg157His (R157H) or p.Gly154Ser (G154S)—plus biochemical experiments. Most detailed mechanistic work instead uses p.Arg120Gly (R120G), an αB-crystallinopathy allele primarily associated with desmin-related myofibrillar disease. Accordingly, R120G findings are supportive pathway evidence, not proof that every DCM1II variant acts through aggregation. Open Targets maps MONDO:0014073 specifically to CRYAB and links the association to PMID 16793013 and PMID 16483541. (OpenTargets Search: Dilated cardiomyopathy 1II, thorkelsson2024roleofthe pages 5-6, thorkelsson2024roleofthe pages 6-8)

The most useful database-ready summary is provided below.

Table: Compact curation of the identity, genetics, phenotype, mechanism, diagnosis, treatment, ontology mappings, and major evidence limitations of CRYAB-associated dilated cardiomyopathy 1II.

1. Disease information

Definition

DCM is defined clinically by left-ventricular or biventricular dilation and systolic dysfunction not sufficiently explained by coronary artery disease, hypertension, abnormal loading, congenital disease, or valvular disease. DCM1II is the CRYAB-associated molecular subtype. The phenotype can be predominantly cardiac, although other CRYAB alleles produce cataract, myofibrillar/distal myopathy, respiratory disease, restrictive cardiomyopathy, or hypertrophic cardiomyopathy. “αB-crystallinopathy” is therefore broader than DCM1II. (thorkelsson2024roleofthe pages 5-6, sarparanta2020neuromusculardiseasesdue pages 17-19, sorella2025diagnosisandmanagement pages 1-2)

Identifiers and synonyms

• MONDO: MONDO:0014073.
• Disease name: Dilated cardiomyopathy 1II.
• Synonyms: cardiomyopathy, dilated, 1II; DCM1II; CRYAB-related DCM; αB-crystallin-related dilated cardiomyopathy.
• Causal association: CRYAB, Ensembl target ENSG00000109846. (OpenTargets Search: Dilated cardiomyopathy 1II)
• OMIM: the retrieved evidence did not expose the disease’s OMIM accession; it should be verified directly in OMIM rather than inferred.
• Orphanet: no subtype-specific Orphanet identifier was recovered.
• ICD-10: no unique DCM1II code; use the jurisdiction-appropriate dilated-cardiomyopathy code, commonly I42.0, supplemented by the molecular diagnosis.
• ICD-11/MeSH: no subtype-specific identifier was established in the retrieved material; map to the parent DCM concept and retain MONDO plus gene/variant fields.

Data provenance

The disease definition and gene mapping are aggregated resource-level assertions, whereas phenotype, onset, and variant evidence largely derive from individual patients or small pedigrees. A 200-proband DCM screen reported CRYAB variants to be uncommon, emphasizing the absence of a subtype registry or adequately powered cohort. (thorkelsson2024roleofthe pages 12-13)

2. Etiology, risk, protective factors, and gene–environment interaction

Primary cause

DCM1II is caused by pathogenic or likely pathogenic germline CRYAB variants, generally heterozygous missense alleles with dominant inheritance. αB-crystallin normally limits protein misfolding, stabilizes desmin and other cytoskeletal/sarcomeric proteins, protects titin domains, regulates stress responses, and opposes apoptosis. Disease mechanisms are allele dependent. (thorkelsson2024roleofthe pages 4-5, sarparanta2020neuromusculardiseasesdue pages 17-19, thorkelsson2024roleofthe pages 2-4)

Genetic risk factors

• p.Arg157His: reported in a 71-year-old person with DCM and a family history of DCM and sudden cardiac death. Its best-supported functional defect is impaired interaction with cardiac titin N2B rather than overt aggregation. (thorkelsson2024roleofthe pages 5-6, thorkelsson2024roleofthe pages 6-8)
• p.Gly154Ser: reported in a 48-year-old woman with DCM and an affected father; the phenotype included mild LV dilation, moderately reduced ejection fraction, and mildly increased creatine kinase. This allele can also cause late-onset distal myopathy and respiratory involvement, indicating variable expressivity. (thorkelsson2024roleofthe pages 5-6)
• Other CRYAB variants can produce restrictive, hypertrophic, myofibrillar, ocular, or multisystem phenotypes and should not automatically be curated as DCM1II. (sarparanta2020neuromusculardiseasesdue pages 17-19, thorkelsson2024roleofthe pages 2-4)

No disease-specific modifier gene, founder variant, carrier frequency, or validated protective allele has been established. Recent general-DCM GWAS work supports a polygenic contribution to penetrance, but this has not been demonstrated specifically in CRYAB families. General DCM data indicate that polygenic background modifies penetrance of rare variants and that higher body weight and systolic blood pressure are potentially actionable causal contributors; these should be treated as plausible DCM1II modifiers, not proven subtype-specific risks. (ramoslopez2026epidemiologyofnonischaemic pages 12-13)

Environmental and lifestyle risks

For DCM generally, viral/autoimmune inflammation, alcohol, cardiotoxic drugs, metabolic disorders, hypertension, obesity, pregnancy, and sustained tachyarrhythmia may act as causes or “second hits.” No CRYAB-specific exposure effect size is available. Because αB-crystallin is stress inducible, oxidative, mechanical, metabolic, or proteotoxic stress could plausibly expose reduced chaperone reserve, but direct human G×E evidence in DCM1II is absent. (thorkelsson2024roleofthe pages 2-4, chao2024researchlandscapeof pages 1-2, ramoslopez2026epidemiologyofnonischaemic pages 12-13)

Protective factors

There are no validated genetic or environmental protective factors specific to DCM1II. Avoiding alcohol excess, cardiotoxic drugs, uncontrolled blood pressure, obesity, and illicit stimulants is rational general DCM prevention. Exercise activates αB-crystallin in healthy muscle, but this does not establish vigorous exercise as protective in CRYAB carriers; exercise prescriptions should follow cardiomyopathy risk assessment.

3. Phenotypes

Subtype-specific frequencies cannot be calculated from the small number of reported patients.

• Dilated cardiomyopathy — sign/imaging phenotype. Adult-to-late onset in the principal reports; severity ranges from mild LV dilation and moderately depressed EF to advanced biventricular disease. Suggested HPO: HP:0001644. (thorkelsson2024roleofthe pages 5-6, orlando2025anunusualcase pages 1-2)
• Reduced LV systolic function — imaging/functional abnormality. Usually progressive or variable; causes reduced exercise tolerance and heart-failure symptoms. Suggested HPO: decreased left-ventricular ejection fraction.
• Heart failure — symptom/sign complex. Dyspnea, fatigue, exercise intolerance, edema, and orthopnea are expected when systolic dysfunction becomes clinically important. Suggested HPO: congestive heart failure, exercise intolerance, dyspnea.
• Arrhythmia/conduction disease and sudden cardiac death — electrophysiological outcome. A family history of sudden death was reported with R157H, but subtype-specific incidence is unknown. Suggested HPO: cardiac arrhythmia, sudden cardiac death. (thorkelsson2024roleofthe pages 5-6)
• Cardiac fibrosis — CMR/histopathology. A newer CRYAB case had diffuse endocardial/subendocardial fibrosis, altered fiber architecture, and anisonucleosis. Suggested HPO: myocardial fibrosis. (orlando2025anunusualcase pages 2-4)
• Atrioventricular-valve regurgitation — secondary manifestation. Functional mitral and tricuspid regurgitation may result from chamber remodeling; severe disease can require intervention. (orlando2025anunusualcase pages 2-4, orlando2025anunusualcase pages 1-2)
• Elevated CK — laboratory abnormality. Mild elevation occurred in the G154S DCM patient and may indicate subclinical skeletal-muscle involvement. Suggested HPO: elevated serum creatine kinase. (thorkelsson2024roleofthe pages 5-6)
• Distal myopathy, respiratory insufficiency, and cataract — allele-dependent extracardiac phenotypes. These are αB-crystallinopathy features, not obligatory DCM1II findings. Suggested HPO: distal muscle weakness, respiratory insufficiency, cataract. (sarparanta2020neuromusculardiseasesdue pages 17-19, thorkelsson2024roleofthe pages 5-6)

Quality of life: no DCM1II-specific EQ-5D, SF-36, KCCQ, or PROMIS study exists. General systolic-HF evidence indicates that higher NYHA class, breathlessness, fatigue, and inability to maintain usual activities are major determinants of impaired health-related quality of life; extrapolation should be labeled general HF evidence.

4. Genetic and molecular information

Gene and protein

• Gene: CRYAB; alias HSPB5.
• Protein: αB-crystallin, a small heat-shock protein and ATP-independent molecular chaperone.
• Location: chromosome 11; one source describes the gene as approximately 3.2 kb. Exact HGNC ID, cytoband, canonical transcript, and genome-build coordinates should be normalized directly against current HGNC/Ensembl records before ingestion. (orlando2025anunusualcase pages 1-2)
• Expression: particularly abundant in cardiac and skeletal muscle—reported at up to 3% of soluble protein—and localized to cytoplasm, Z-discs, I-bands, and cardiac intercalated discs. (sarparanta2020neuromusculardiseasesdue pages 17-19)

Pathogenic variants and interpretation

(thorkelsson2024roleofthe pages 5-6, thorkelsson2024roleofthe pages 6-8, sarparanta2020neuromusculardiseasesdue pages 19-20, cannone2023humanmutatedmyot pages 12-13)

Allele frequencies were not available in the retrieved evidence. Causal DCM alleles are expected to be rare, but gnomAD ancestry-specific frequency, read quality, transcript consequence, ClinVar assertions, familial segregation, and phenotype compatibility must be reviewed for each patient. All established inherited cases are germline; there is no evidence that somatic CRYAB mutation causes DCM1II.

Functional consequence

R157H chiefly appears to produce a selective protein-interaction defect, whereas R120G produces dominant-negative chaperone dysfunction and proteotoxic aggregation. G154S may perturb myofibrillar proteostasis, but its cardiac mechanism remains underdefined. Thus, “dominant negative” should not be assigned universally to all CRYAB variants. (thorkelsson2024roleofthe pages 6-8, ruparelia2012myofibrillarmyopathiesand pages 8-10, thorkelsson2024roleofthe pages 4-5)

Modifiers, epigenetics, and chromosomal abnormalities

No validated DCM1II-specific modifier gene, DNA-methylation signature, histone alteration, chromatin mechanism, recurrent copy-number variant, translocation, inversion, or aneuploidy was identified. General polygenic background and environmental stress are plausible penetrance modifiers. (ramoslopez2026epidemiologyofnonischaemic pages 12-13)

5. Environmental information

No toxin, pollutant, occupational exposure, radiation source, or infectious organism is uniquely causal for DCM1II. Evaluation should nevertheless exclude general acquired DCM causes: substantial alcohol exposure, anthracyclines or other cardiotoxic drugs, cocaine/amphetamines, nutritional/endocrine abnormalities, pregnancy-associated disease, sustained tachycardia, myocarditis, Chagas disease where epidemiologically relevant, and autoimmune disease. A recent CRYAB case underwent exclusion of Chagas disease, alcohol, drug/toxin, myocarditis, autoimmune, coronary, and other secondary causes before the genetic diagnosis was accepted. (orlando2025anunusualcase pages 1-2)

Lifestyle management should address smoking, alcohol, body weight, blood pressure, diabetes, sodium intake when congested, and safe individualized physical activity. In general nonischemic DCM, diabetes was associated with worse remodeling and outcomes, but no corresponding CRYAB-only estimate exists.

6. Mechanism and pathophysiology

Ordered causal chain

1. A heterozygous CRYAB missense variant leads to altered αB-crystallin structure, oligomer behavior, stability, or client-protein interaction.
2. For R157H, impaired αB-crystallin binding to cardiac titin N2B and reduced I-band localization lead to deficient stress protection of the cardiomyocyte spring/sarcomere; the next step is biologically plausible but not fully demonstrated in patients. (thorkelsson2024roleofthe pages 6-8)
3. For G154S, altered myofibrillar proteostasis leads to CRYAB/desmin-positive aggregation in skeletal muscle and structural dysfunction in overexpression models; equivalent aggregate pathology in human DCM myocardium remains unproven. (thorkelsson2024roleofthe pages 5-6, cannone2023humanmutatedmyot pages 12-13)
4. Branch A—sarcomeric/mechanical: defective titin/cytoskeletal support leads to impaired force transmission and reduced stress tolerance, which results in cardiomyocyte dysfunction.
5. Branch B—proteotoxic, supported mainly by R120G: defective chaperoning leads to misfolded CRYAB and desmin oligomers/aggregates, which overload or inhibit ubiquitin–proteasome and autophagy–lysosome quality control. (thorkelsson2024roleofthe pages 5-6, thorkelsson2024roleofthe pages 4-5)
6. Proteostasis failure leads to Z-disc/myofibril disorganization, mitochondrial architectural and energetic abnormalities, redox imbalance, and increased apoptosis. These steps are demonstrated mainly in R120G cells/mice and inferred for DCM1II alleles lacking direct myocardial study. (ruparelia2012myofibrillarmyopathiesand pages 8-10, sarparanta2020neuromusculardiseasesdue pages 19-20)
7. Cardiomyocyte dysfunction/death leads to compensatory hypertrophy, fibroblast activation, interstitial fibrosis, and adverse ventricular remodeling.
8. Remodeling results in LV dilation, reduced ejection fraction, functional mitral/tricuspid regurgitation, arrhythmogenic substrate, and clinical heart failure. (orlando2025anunusualcase pages 2-4, thorkelsson2024roleofthe pages 6-8)
9. Progressive pump or electrical failure can result in advanced HF, transplantation, or sudden cardiac death; subtype-specific risks are unknown.

Mechanistic detail and evidence level

Normal protein biology: αB-crystallin binds denatured proteins and supports solubility, desmin/intermediate-filament assembly, actin/tubulin homeostasis, and titin-domain stability. Stress phosphorylation at Ser19, Ser45, and Ser59 promotes cytoskeleton translocation. Suggested GO processes: chaperone-mediated protein folding; response to heat; response to oxidative stress; intermediate-filament organization; sarcomere organization; negative regulation of apoptosis. Suggested cellular components: cytosol, Z disc, I band, intermediate filament, protein-containing complex. (sarparanta2020neuromusculardiseasesdue pages 17-19, thorkelsson2024roleofthe pages 2-4)

R157H-specific evidence: the variant reduces binding to the cardiac titin N2B region and I-band localization but retains interaction with a skeletal-muscle titin domain, offering a possible explanation for cardiac predominance. It forms smaller oligomers during heat stress, has lower thermal stability, and retains chaperone activity. This argues against a universal aggregate-first mechanism. (thorkelsson2024roleofthe pages 6-8)

R120G supporting model biology: abnormal dimers/oligomers, dominant-negative behavior, mutant CRYAB/desmin aggregation, loss of striation, reductive stress, autophagy disturbance, mitochondrial abnormalities, fibrosis, apoptosis, dilation, and systolic failure have been demonstrated. Severity depends strongly on expression: high-expression transgenic mice died at 5–7 months and intermediate-expression mice at 12–16 months, whereas physiological knock-in mice reproduced cataract/myopathy without cardiac lethality. This expression dependence is a major translational limitation. (thorkelsson2024roleofthe pages 6-8, thorkelsson2024roleofthe pages 4-5, sarparanta2020neuromusculardiseasesdue pages 19-20)

Autophagy: R120G increased cardiomyocyte autophagic activity more than twofold as an adaptive response; reducing Beclin-1 worsened aggregate accumulation, produced a threefold increase in interstitial fibrosis, accelerated dysfunction, and caused earlier death. Autophagy is therefore compensatory in this proteotoxic model rather than simply pathogenic. (thorkelsson2024roleofthe pages 5-6)

Redox and metabolism: R120G mice show increased G6PD, glutathione reductase, and glutathione peroxidase activity and reductive stress; lowering G6PD rescued proteotoxic and cardiomyopathic phenotypes. Mitochondrial disorganization and reduced oxidative capacity plausibly contribute to energy failure. Again, direct confirmation in R157H/G154S human myocardium is lacking. (thorkelsson2024roleofthe pages 4-5, sarparanta2020neuromusculardiseasesdue pages 19-20)

Immune involvement: there is no evidence for primary autoimmunity or immunodeficiency in DCM1II. Inflammation is more likely downstream of cardiomyocyte injury or a general-DCM second hit.

Molecular profiling and advanced technology

No DCM1II-specific human single-cell, spatial-transcriptomic, proteomic, metabolomic, lipidomic, or epigenomic cohort was identified. General 2024 DCM GWAS studies analyzed thousands of cases and used tissue/cell enrichment and single-nucleus transcriptomics to prioritize cardiomyocytes, contractile pathways, cellular states, and intercellular communication, but these results cannot be assigned specifically to CRYAB disease. A 2024 preprint reported mitochondrial uptake and mitophagy of R120G-CRYAB, while a separate 2024 project suggested export through extracellular vesicles; both remain variant/model-specific. (rawnsley2026mitophagyfacilitatescytosolic pages 50-55, ivezich2024secretionofthe pages 48-52)

Suggested cell terms: cardiomyocyte CL:0000746; ventricular cardiomyocyte; cardiac fibroblast; vascular endothelial cell; tissue macrophage. Cardiomyocytes are directly implicated; fibroblast and immune-cell roles are downstream/inferred.

7. Anatomical structures affected

• Primary organ: heart (UBERON:0000948), especially ventricular myocardium and left ventricle.
• Primary tissue: striated cardiac muscle/myocardium.
• Primary cell: cardiomyocyte (CL:0000746).
• Secondary structures: right ventricle and atria in advanced remodeling; mitral/tricuspid apparatus through functional regurgitation; conduction system through arrhythmia risk.
• Allele-dependent extracardiac tissues: skeletal muscle and respiratory muscle; ocular lens in cataract-associated αB-crystallinopathies.
• Subcellular sites: cytosol, Z disc, I band, intermediate filaments/desmin network, sarcomere, mitochondria, autophagosome/lysosome, proteasome-associated protein complexes.
• Lateralization: not applicable; myocardial disease is not a unilateral disorder.

A 42-year-old CRYAB patient demonstrated biatrial and biventricular dilation, endocardial/subendocardial fibrosis, and severe valve regurgitation, illustrating advanced multichamber involvement. (orlando2025anunusualcase pages 2-4, orlando2025anunusualcase pages 1-2)

8. Temporal development

The best-described isolated-DCM cases were diagnosed in middle or late adulthood—approximately 48 and 71 years—supporting adult/late, usually insidious onset. Other CRYAB alleles may present in childhood with cataract or myopathy, but that should not define DCM1II onset. (thorkelsson2024roleofthe pages 5-6, sarparanta2020neuromusculardiseasesdue pages 17-19)

A practical course model is:

1. Genotype-positive/phenotype-negative stage: normal function or subtle ECG/imaging abnormality.
2. Early phenotype: mild dilation, impaired strain, scar, arrhythmia, or modest EF reduction.
3. Overt DCM: dilation plus systolic dysfunction, exercise limitation, and HF symptoms.
4. Advanced disease: biventricular failure, severe functional regurgitation, fibrosis, ventricular arrhythmia, mechanical support, or transplantation.

Progression is variable and age dependent; penetrance and median time between stages are unknown. General DCM can undergo treatment-associated reverse remodeling, but “recovered” function does not necessarily eliminate genetic risk. The critical intervention window is before irreversible fibrosis and advanced dilation—hence cascade screening and longitudinal surveillance.

9. Inheritance and population

Inheritance

The principal isolated-DCM reports support autosomal-dominant germline inheritance, with variable, likely age-dependent penetrance and expressivity. One recent heterozygous CRYAB case appeared de novo after reportedly negative first- and second-degree family histories. Germline mosaicism, anticipation, founder effects, consanguinity effects, and carrier frequency have not been established. (thorkelsson2024roleofthe pages 5-6, orlando2025anunusualcase pages 1-2)

Epidemiology

No prevalence or incidence is available for DCM1II. CRYAB variants were rare in a consecutive series of 200 unrelated DCM probands. General DCM prevalence estimates vary by ascertainment: older conventional studies reported approximately 14–59 per 100,000, whereas contemporary imaging-based estimates approach 1 in 220–250. Historical incidence was approximately 6 per 100,000 person-years in one population. These figures must not be stored as DCM1II prevalence. (thorkelsson2024roleofthe pages 12-13, bergan2025systematicreviewmetaanalysis pages 2-4, ramoslopez2026epidemiologyofnonischaemic pages 3-5, ramoslopez2026epidemiologyofnonischaemic pages 1-2)

A recent meta-analysis of 99 studies and 37,525 participants found an overall female proportion of 0.30, equivalent to a male:female ratio of 2.38:1; genotype-positive DCM showed a similar ratio. This suggests sex-modified penetrance or diagnostic bias in general DCM, but no CRYAB-specific sex ratio exists. (bergan2025systematicreviewmetaanalysis pages 2-4)

No population-specific founder allele or geographical concentration has been demonstrated for R157H or G154S.

10. Diagnostics

Clinical diagnostic workflow

1. Phenotype the cardiomyopathy: history, three- to four-generation pedigree, physical examination, 12-lead ECG, ambulatory rhythm monitoring, transthoracic echocardiography, and CMR.
2. Measure severity/alternative causes: BNP or NT-proBNP, high-sensitivity troponin, CBC, electrolytes, renal/liver/thyroid studies, glucose/HbA1c, iron indices, CK, and exposure/infectious/autoimmune tests when indicated.
3. Exclude mimics: ischemic disease, pressure or volume overload, valvular/congenital disease, myocarditis, infiltrative disease, tachycardia-mediated disease, toxins, endocrine/metabolic causes, and neuromuscular syndromes.
4. Define tissue phenotype: CMR for volumes, EF, edema and late-gadolinium enhancement; coronary imaging according to pretest probability. Endomyocardial biopsy is reserved for cases in which myocarditis, infiltrative/storage disease, or another biopsy-directed diagnosis remains plausible.
5. Genetic evaluation: pretest counseling followed by a curated cardiomyopathy panel that includes definitive DCM genes and CRYAB where phenotype suggests αB-crystallinopathy. Interpret variants under ACMG/AMP criteria with ClinVar/ClinGen, gnomAD, segregation, functional evidence, and phenotype matching. (sorella2025diagnosisandmanagement pages 1-2, sorella2025diagnosisandmanagement pages 2-3)

A guideline synthesis states that evaluation should be multiparametric and identifies echocardiography as first-line, CMR for functional/tissue characterization, and BNP/troponin for diagnosis, severity, prognosis, and treatment-response assessment. (sorella2025diagnosisandmanagement pages 1-2, sorella2025diagnosisandmanagement pages 2-3)

Genetic test selection

• Multigene panel: preferred initial test because DCM is highly heterogeneous and CRYAB phenotypes overlap other cardiomyopathies/myopathies.
• Single-gene CRYAB sequencing: reasonable after a known familial variant or a highly specific αB-crystallinopathy phenotype.
• WES/WGS: useful for panel-negative familial disease, atypical syndromic presentations, splice/noncoding variants, and structural variation; WGS may improve noncoding and CNV detection.
• RNA sequencing: potentially useful for suspected splice variants, but no validated DCM1II RNA diagnostic exists.
• CMA/karyotype/FISH: low yield for isolated adult DCM1II; reserve for congenital anomalies, developmental disease, or suspected chromosomal imbalance.
• Mitochondrial DNA/repeat-expansion tests: not routine for isolated DCM1II; use when phenotype indicates an alternative syndrome.

Family screening

When a pathogenic familial CRYAB variant is established, offer targeted cascade testing. First-degree relatives who carry the variant—or untested relatives in an informative family—require periodic ECG and cardiac imaging, with frequency individualized by age, symptoms, family history, and guideline recommendations. A relative testing negative for the established familial pathogenic variant can generally be released from variant-based surveillance unless clinical findings independently warrant follow-up.

Differential diagnosis

Exclude ischemic cardiomyopathy, myocarditis, arrhythmogenic cardiomyopathy, LMNA/FLNC/DSP/RBM20/BAG3/DES-related disease, tachycardia-induced cardiomyopathy, alcohol or drug toxicity, peripartum cardiomyopathy, endocrine/metabolic disease, hemochromatosis, amyloidosis, sarcoidosis, valvular disease, and neuromuscular myofibrillar myopathy. Cataract, distal weakness, CK elevation, dysphagia, or respiratory weakness should prompt evaluation for syndromic αB-crystallinopathy.

11. Outcome and prognosis

No DCM1II-specific survival curve, transplant-free survival rate, life-expectancy estimate, or validated prognostic biomarker exists. Reported disease ranges from mild adult LV dysfunction to progressive severe valvular regurgitation and advanced HF. Family sudden death suggests possible arrhythmic risk, but no CRYAB-specific ICD threshold can be supported. (orlando2025anunusualcase pages 2-4, thorkelsson2024roleofthe pages 5-6)

General DCM literature reports five-year mortality as high as 15.5% despite contemporary medical/device therapy, with roughly two-thirds of deaths attributed to pump failure and one-third to sudden death. This is background context, not a DCM1II estimate. (chao2024researchlandscapeof pages 1-2)

General prognostic factors include baseline and serial EF/ventricular size, RV dysfunction, NYHA class, fibrosis/LGE, ventricular arrhythmia, conduction disease, BNP/NT-proBNP, troponin, renal dysfunction, diabetes, and failure to reverse remodel. In a pediatric DCM registry of 794 children, 5.0% died and 14.7% underwent transplantation within one year; worsening LV dilation predicted later death/transplantation. These pediatric data should not be generalized to adult CRYAB DCM but support serial imaging as a principle.

Potential recovery depends on disease stage and treatment. Reverse remodeling may occur with guideline-directed therapy, but continued surveillance is prudent because a genetic substrate persists. Major morbidity includes HF hospitalization, arrhythmia, thromboembolism in appropriate settings, functional regurgitation, exercise limitation, respiratory failure in multisystem alleles, device complications, and transplantation.

12. Treatment

Current clinical management

There is no approved CRYAB-specific therapy. Management follows DCM/HFrEF standards and the patient’s EF, symptoms, rhythm, scar, and hemodynamics:

• ARNI (sacubitril/valsartan) or ACE inhibitor/ARB when ARNI is unsuitable.
• Evidence-based β-blocker.
• Mineralocorticoid-receptor antagonist.
• SGLT2 inhibitor.
• Loop diuretic for congestion.
• Additional therapy such as ivabradine, hydralazine/isosorbide dinitrate, anticoagulation, or antiarrhythmic treatment only for standard indications.
• ICD for primary/secondary prevention according to EF, arrhythmic history, scar, genotype and guideline criteria; no CRYAB-specific indication has been validated.
• CRT for appropriate electrical dyssynchrony and systolic dysfunction.
• Valve intervention when severe secondary regurgitation persists despite optimized therapy.
• LV assist device or heart transplantation for refractory advanced HF.
• Cardiac rehabilitation, vaccinations, nutritional counseling, smoking cessation, and individualized activity advice. (orlando2025anunusualcase pages 1-2, chao2024researchlandscapeof pages 8-10)

Suggested NCIt intervention concepts include angiotensin-receptor neprilysin inhibitor therapy, beta-adrenergic blockade, mineralocorticoid-receptor antagonist therapy, SGLT2 inhibition, diuretic therapy, implantable cardioverter-defibrillator placement, cardiac resynchronization therapy, ventricular-assist-device therapy, heart transplantation, and cardiac rehabilitation. Exact NCIt codes should be release-validated.

Experimental mechanisms

R120G models—not R157H/G154S clinical trials—suggest several experimental approaches:

• Enhancing autophagy/TFEB signaling to clear aggregates and normalize desmin.
• Improving proteasomal degradation.
• Anti-aggregation compounds such as molecular tweezers.
• Modulating reductive stress/G6PD.
• JAK inhibition and mitophagy modulation in emerging preclinical studies.

These approaches remain preclinical and variant mismatched. The clinical-trial search recovered no relevant CRYAB-targeted gene therapy, antisense, siRNA, or CRISPR trial. (thorkelsson2024roleofthe pages 5-6, rawnsley2026mitophagyfacilitatescytosolic pages 50-55, thorkelsson2024roleofthe pages 4-5)

Pharmacogenomics

No CRYAB genotype–drug metabolism or efficacy rule is established. Standard pharmacogenomic considerations apply to individual drugs, but they are not disease specific.

13. Prevention

Primary prevention

The inherited variant cannot currently be prevented after conception. Risk reduction should include avoiding cardiotoxic exposures and alcohol excess, controlling blood pressure, diabetes and weight, abstaining from smoking and stimulants, and promptly treating sustained arrhythmias or infections. No vaccine prevents genetic DCM1II; routine influenza, COVID-19 and pneumococcal vaccination is appropriate according to age and HF guidance.

Secondary prevention

• Genetic counseling and cascade testing after identification of a familial pathogenic variant.
• Longitudinal ECG, rhythm assessment, echocardiography and—where indicated—CMR in carriers.
• Early guideline-directed therapy once structural/functional disease emerges.
• Arrhythmia and sudden-death risk assessment based on the full clinical profile.

Tertiary prevention

Optimize HF therapy, prevent decompensation, manage arrhythmia/thromboembolic risk, provide cardiac rehabilitation, and use ICD/CRT/advanced HF therapies according to standard criteria.

Reproductive counseling

For an autosomal-dominant pathogenic variant, each child generally has a 50% chance of inheriting the variant, although penetrance and severity are unpredictable. Discuss prenatal diagnosis and preimplantation genetic testing for a confirmed familial pathogenic variant. VUS findings should not be used alone for predictive testing or reproductive selection.

14. Other species and naturally occurring disease

CRYAB is evolutionarily conserved across vertebrates and supports lens, skeletal-muscle and cardiac proteostasis. No well-established naturally occurring veterinary disorder equivalent to human DCM1II, breed predisposition, VBO term, or zoonotic relevance was identified. This is a noninfectious inherited disease and has no cross-species transmission.

The 2023 zebrafish experiment expressed human CRYAB G154S in embryos. Mutant-expressing fish had reduced myofiber density, sarcomere disorganization, granular aggregates, motor impairment, altered BMP signaling, and increased mortality. However, it was a transient overexpression model, the relevant residue was not conserved in zebrafish, and wild-type overexpression also caused abnormalities. It is therefore a mechanistic model, not naturally occurring zebrafish DCM. (cannone2023humanmutatedmyot pages 2-5, cannone2023humanmutatedmyot pages 12-13)

Suggested taxa for model annotation: Homo sapiens NCBI Taxon 9606, Mus musculus 10090, and Danio rerio 7955.

15. Model organisms and experimental systems

Mouse

Cardiac-specific Cryab-R120G transgenic mice reproduce CRYAB/desmin aggregation, Z-disc disruption, mitochondrial abnormalities, fibrosis, ventricular remodeling, systolic failure, and premature death. High expressors die around 5–7 months and intermediate expressors around 12–16 months. Physiological knock-in mice show cataract and skeletal myopathy but may lack lethal cardiomyopathy, demonstrating overexpression-dependent severity. These models are highly informative for proteotoxicity but imperfect for R157H/G154S DCM1II. (thorkelsson2024roleofthe pages 6-8, sarparanta2020neuromusculardiseasesdue pages 19-20)

Cryab/Hspb2-deficient mice and variant knock-ins are useful for studying stress responses, metabolism, ischemia, hypertrophy, and apoptosis, but combined deletion and species differences complicate attribution to human CRYAB disease.

Zebrafish

Transient human CRYAB-G154S overexpression models myofibrillar disorganization, aggregation, motor dysfunction and mortality. Advantages are rapid development and drug-screening potential; limitations include nonconserved residue, mosaic/dosage effects, embryonic rather than adult disease, and incomplete cardiac phenotyping. (cannone2023humanmutatedmyot pages 2-5, cannone2023humanmutatedmyot pages 12-13)

Cellular and human-engineered systems

Cultured cardiomyocytes expressing R120G are used to quantify aggregates, autophagy, proteasome function, toxicity and rescue. Patient-derived or CRISPR knock-in hiPSC cardiomyocytes and engineered heart tissues are the most promising platforms for studying human-specific contractility and variant-specific mechanisms. However, no mature, independently replicated R157H or G154S hiPSC natural-history platform was identified in the retrieved 2023–2024 literature.

Model applications and limitations

Models support investigation of chaperone–client interactions, titin/desmin biology, protein quality control, mitochondrial injury, redox imbalance, aggregate clearance, and drug screening. Their principal limitation is allelic mismatch: the extensive R120G proteotoxicity literature cannot establish that R157H—the best-characterized isolated-DCM allele—causes disease through the same pathway.

Recent developments, 2023–2024

1. 2023 G154S zebrafish work: human mutant CRYAB expression produced myofibrillar pathology and motor impairment, offering a tractable screening model but also revealing substantial overexpression caveats. The abstract states: “transgenic zebrafish showed morphological defects that were more severe in those overexpressing mutant genes” and developed a myopathic phenotype with protein aggregates. Published 14 July 2023; DOI: https://doi.org/10.3390/ijms241411483. (cannone2023humanmutatedmyot pages 1-2, cannone2023humanmutatedmyot pages 12-13)
2. 2024 CRYAB synthesis: Thorkelsson and Chin emphasized allele-specific mechanisms—desmin aggregation, reductive stress, and calcineurin–NFAT signaling across different cardiomyopathy alleles. Published February 2024; DOI: https://doi.org/10.3390/ijms25052826. (thorkelsson2024roleofthe pages 5-6, thorkelsson2024roleofthe pages 6-8)
3. 2024 general DCM genetics: contemporary reviews estimate that an identifiable genetic cause exists in up to approximately 40% of familial DCM, while cautioning that many of more than 200 proposed genes lack strong pathogenicity evidence. This reinforces conservative CRYAB variant interpretation rather than relying on panel inclusion alone. (chao2024researchlandscapeof pages 8-10, sorella2025diagnosisandmanagement pages 1-2)
4. 2024 polygenic architecture: large DCM GWAS analyses identified dozens of loci and used cell/tissue enrichment or single-nucleus transcriptomics to implicate cardiomyocytes and the contractile apparatus. These studies support a rare-variant-plus-polygenic-background model but have not yet yielded a CRYAB-specific penetrance score. (ramoslopez2026epidemiologyofnonischaemic pages 12-13)
5. 2023 ESC framework: the modern approach is phenotype first, followed by etiological evaluation integrating CMR, genetics, family assessment, and multidisciplinary interpretation. (sorella2025diagnosisandmanagement pages 1-2, sorella2025diagnosisandmanagement pages 2-3)

Overall expert assessment

DCM1II is a credible but exceptionally sparse CRYAB-associated disease entity. The most defensible mechanistic annotation is allele specific: R157H impairs αB-crystallin–titin N2B interaction; G154S has limited human cardiac mechanistic evidence but causes myofibrillar dysfunction in experimental systems; and R120G demonstrates how severe αB-crystallin dysfunction can produce proteotoxic cardiomyopathy. Clinical care should therefore combine standard DCM/HFrEF treatment with genetics-led family management, while avoiding premature assignment of aggregate-directed therapy or R120G-derived prognosis to R157H/G154S carriers. Subtype-specific epidemiology, penetrance, outcomes, biomarkers, and treatment response remain major knowledge gaps. (OpenTargets Search: Dilated cardiomyopathy 1II, sorella2025diagnosisandmanagement pages 1-2, thorkelsson2024roleofthe pages 6-8, sarparanta2020neuromusculardiseasesdue pages 19-20)

References

1. (OpenTargets Search: Dilated cardiomyopathy 1II): Open Targets Query (Dilated cardiomyopathy 1II, 1 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.

2. (thorkelsson2024roleofthe pages 5-6): Andres Thorkelsson and Michael T. Chin. Role of the alpha-b-crystallin protein in cardiomyopathic disease. International Journal of Molecular Sciences, Feb 2024. URL: https://doi.org/10.3390/ijms25052826, doi:10.3390/ijms25052826. This article has 22 citations.

3. (thorkelsson2024roleofthe pages 6-8): Andres Thorkelsson and Michael T. Chin. Role of the alpha-b-crystallin protein in cardiomyopathic disease. International Journal of Molecular Sciences, Feb 2024. URL: https://doi.org/10.3390/ijms25052826, doi:10.3390/ijms25052826. This article has 22 citations.

4. (sarparanta2020neuromusculardiseasesdue pages 17-19): J. Sarparanta, P. Jonson, S. Kawan, and B. Udd. Neuromuscular diseases due to chaperone mutations: a review and some new results. International Journal of Molecular Sciences, Feb 2020. URL: https://doi.org/10.3390/ijms21041409, doi:10.3390/ijms21041409. This article has 93 citations.

5. (thorkelsson2024roleofthe pages 2-4): Andres Thorkelsson and Michael T. Chin. Role of the alpha-b-crystallin protein in cardiomyopathic disease. International Journal of Molecular Sciences, Feb 2024. URL: https://doi.org/10.3390/ijms25052826, doi:10.3390/ijms25052826. This article has 22 citations.

6. (orlando2025anunusualcase pages 1-2): Porras Bueno Cristian Orlando, Cruz Buitrago Roberto Hernando, M. Alejandro, Cáceres Méndez Edward Andres, E. Meek, and Ríos Dueñas Edgar Giovanni. An unusual case of 11αb‐crystallin (cryab) mutation as a cause of dilated cardiomyopathy with restrictive physiology: a case report and focused review of the literature. Clinical Case Reports, Mar 2025. URL: https://doi.org/10.1002/ccr3.70213, doi:10.1002/ccr3.70213. This article has 1 citations.

7. (cannone2023humanmutatedmyot pages 2-5): Elena Cannone, Valeria Guglielmi, Giulia Marchetto, Chiara Tobia, Barbara Gnutti, Barbara Cisterna, Paola Tonin, Alessandro Barbon, Gaetano Vattemi, and Marco Schiavone. Human mutated myot and cryab genes cause a myopathic phenotype in zebrafish. Jul 2023. URL: https://doi.org/10.3390/ijms241411483, doi:10.3390/ijms241411483. This article has 6 citations.

8. (orlando2025anunusualcase pages 2-4): Porras Bueno Cristian Orlando, Cruz Buitrago Roberto Hernando, M. Alejandro, Cáceres Méndez Edward Andres, E. Meek, and Ríos Dueñas Edgar Giovanni. An unusual case of 11αb‐crystallin (cryab) mutation as a cause of dilated cardiomyopathy with restrictive physiology: a case report and focused review of the literature. Clinical Case Reports, Mar 2025. URL: https://doi.org/10.1002/ccr3.70213, doi:10.1002/ccr3.70213. This article has 1 citations.

9. (cannone2023humanmutatedmyot pages 12-13): Elena Cannone, Valeria Guglielmi, Giulia Marchetto, Chiara Tobia, Barbara Gnutti, Barbara Cisterna, Paola Tonin, Alessandro Barbon, Gaetano Vattemi, and Marco Schiavone. Human mutated myot and cryab genes cause a myopathic phenotype in zebrafish. Jul 2023. URL: https://doi.org/10.3390/ijms241411483, doi:10.3390/ijms241411483. This article has 6 citations.

10. (thorkelsson2024roleofthe pages 4-5): Andres Thorkelsson and Michael T. Chin. Role of the alpha-b-crystallin protein in cardiomyopathic disease. International Journal of Molecular Sciences, Feb 2024. URL: https://doi.org/10.3390/ijms25052826, doi:10.3390/ijms25052826. This article has 22 citations.

11. (sarparanta2020neuromusculardiseasesdue pages 19-20): J. Sarparanta, P. Jonson, S. Kawan, and B. Udd. Neuromuscular diseases due to chaperone mutations: a review and some new results. International Journal of Molecular Sciences, Feb 2020. URL: https://doi.org/10.3390/ijms21041409, doi:10.3390/ijms21041409. This article has 93 citations.

12. (sorella2025diagnosisandmanagement pages 1-2): Anna Sorella, Kristian Galanti, Lorena Iezzi, Sabina Gallina, Selma F Mohammed, Neha Sekhri, Mohammed Majid Akhtar, Sanjay K Prasad, Choudhary Anwar Ahmed Chahal, Fabrizio Ricci, and Mohammed Yunus Khanji. Diagnosis and management of dilated cardiomyopathy: a systematic review of clinical practice guidelines and recommendations. European Heart Journal. Quality of Care & Clinical Outcomes, 11:206-222, Dec 2025. URL: https://doi.org/10.1093/ehjqcco/qcae109, doi:10.1093/ehjqcco/qcae109. This article has 45 citations.

13. (sorella2025diagnosisandmanagement pages 2-3): Anna Sorella, Kristian Galanti, Lorena Iezzi, Sabina Gallina, Selma F Mohammed, Neha Sekhri, Mohammed Majid Akhtar, Sanjay K Prasad, Choudhary Anwar Ahmed Chahal, Fabrizio Ricci, and Mohammed Yunus Khanji. Diagnosis and management of dilated cardiomyopathy: a systematic review of clinical practice guidelines and recommendations. European Heart Journal. Quality of Care & Clinical Outcomes, 11:206-222, Dec 2025. URL: https://doi.org/10.1093/ehjqcco/qcae109, doi:10.1093/ehjqcco/qcae109. This article has 45 citations.

14. (chao2024researchlandscapeof pages 8-10): Tiantian Chao, Yaru Ge, Jinghui Sun, and Chenglong Wang. Research landscape of genetics in dilated cardiomyopathy: insight from a bibliometric analysis. Frontiers in Cardiovascular Medicine, Jul 2024. URL: https://doi.org/10.3389/fcvm.2024.1362551, doi:10.3389/fcvm.2024.1362551. This article has 9 citations and is from a peer-reviewed journal.

15. (thorkelsson2024roleofthe pages 12-13): Andres Thorkelsson and Michael T. Chin. Role of the alpha-b-crystallin protein in cardiomyopathic disease. International Journal of Molecular Sciences, Feb 2024. URL: https://doi.org/10.3390/ijms25052826, doi:10.3390/ijms25052826. This article has 22 citations.

16. (ramoslopez2026epidemiologyofnonischaemic pages 12-13): Noemí Ramos-López, Fernando Domínguez, Juan Pablo Ochoa, Enrique Lara-Pezzi, and Pablo Garcia-Pavia. Epidemiology of non-ischaemic dilated cardiomyopathy. Nature Reviews Cardiology, May 2026. URL: https://doi.org/10.1038/s41569-026-01300-z, doi:10.1038/s41569-026-01300-z. This article has 0 citations and is from a domain leading peer-reviewed journal.

17. (chao2024researchlandscapeof pages 1-2): Tiantian Chao, Yaru Ge, Jinghui Sun, and Chenglong Wang. Research landscape of genetics in dilated cardiomyopathy: insight from a bibliometric analysis. Frontiers in Cardiovascular Medicine, Jul 2024. URL: https://doi.org/10.3389/fcvm.2024.1362551, doi:10.3389/fcvm.2024.1362551. This article has 9 citations and is from a peer-reviewed journal.

18. (ruparelia2012myofibrillarmyopathiesand pages 8-10): Avnika Ruparelia, Raquel Vaz, and Robert Bryson-Richardso. Myofibrillar myopathies and the z-disk associated proteins. ArXiv, pages 317-358, Aug 2012. URL: https://doi.org/10.5772/50110, doi:10.5772/50110. This article has 8 citations.

19. (rawnsley2026mitophagyfacilitatescytosolic pages 50-55): David R. Rawnsley, Moydul Islam, Chen Zhao, Xumin Guan, Yasaman Kargar Gaz Kooh, Adelita Mendoza, Honora Navid, Minu Kumari, Phalgun Pandi, John T. Murphy, Jess Nigro, Attila Kovacs, Lina Greenberg, Kartik Mani, Michael Greenberg, Nathaniel Huebsch, Xiucui Ma, and Abhinav Diwan. Mitophagy facilitates cytosolic proteostasis to preserve cardiac function. Circulation Research, Aug 2026. URL: https://doi.org/10.1161/circresaha.126.328328, doi:10.1161/circresaha.126.328328. This article has 3 citations and is from a highest quality peer-reviewed journal.

20. (ivezich2024secretionofthe pages 48-52): SA Ivezich. Secretion of the mutant protein alphab-crystallin r120g in extracellular vesicles. Unknown journal, 2024.

21. (bergan2025systematicreviewmetaanalysis pages 2-4): Natalie Bergan, Ishika Prachee, Lara Curran, Kathryn A. McGurk, Chang Lu, Antonio de Marvao, Wenjia Bai, Brian P. Halliday, John Gregson, Declan P. O’Regan, James S. Ware, and Upasana Tayal. Systematic review, meta-analysis, and population study to determine the biologic sex ratio in dilated cardiomyopathy. Feb 2025. URL: https://doi.org/10.1161/circulationaha.124.070872, doi:10.1161/circulationaha.124.070872. This article has 21 citations and is from a highest quality peer-reviewed journal.

22. (ramoslopez2026epidemiologyofnonischaemic pages 3-5): Noemí Ramos-López, Fernando Domínguez, Juan Pablo Ochoa, Enrique Lara-Pezzi, and Pablo Garcia-Pavia. Epidemiology of non-ischaemic dilated cardiomyopathy. Nature Reviews Cardiology, May 2026. URL: https://doi.org/10.1038/s41569-026-01300-z, doi:10.1038/s41569-026-01300-z. This article has 0 citations and is from a domain leading peer-reviewed journal.

23. (ramoslopez2026epidemiologyofnonischaemic pages 1-2): Noemí Ramos-López, Fernando Domínguez, Juan Pablo Ochoa, Enrique Lara-Pezzi, and Pablo Garcia-Pavia. Epidemiology of non-ischaemic dilated cardiomyopathy. Nature Reviews Cardiology, May 2026. URL: https://doi.org/10.1038/s41569-026-01300-z, doi:10.1038/s41569-026-01300-z. This article has 0 citations and is from a domain leading peer-reviewed journal.

24. (cannone2023humanmutatedmyot pages 1-2): Elena Cannone, Valeria Guglielmi, Giulia Marchetto, Chiara Tobia, Barbara Gnutti, Barbara Cisterna, Paola Tonin, Alessandro Barbon, Gaetano Vattemi, and Marco Schiavone. Human mutated myot and cryab genes cause a myopathic phenotype in zebrafish. Jul 2023. URL: https://doi.org/10.3390/ijms241411483, doi:10.3390/ijms241411483. This article has 6 citations.

Artifacts

• Edison artifact artifact-00

Reference Validation

Checked with linkml-reference-validator 0.2.1.

All extracted references resolved successfully.

Term Validation

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

Terms whose name is worth a second look

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

• CL:0000746 (3 mentions) - the report calls it "Cardiac muscle cell/cardiomyocyte"; CL calls it cardiac muscle cell

Every term resolved, and every label the report gave matched.