Real-World Data Reveals Low Penetrance of IRD-Associated Genotypes
Overview
A population-based study using large genomic biobanks found that only 9% to 28% of individuals with inherited retinal disease (IRD)-associated genotypes exhibit clinical signs of retinal degeneration. This challenges prior assumptions of near-complete penetrance and suggests that additional genetic or environmental factors influence disease manifestation.
Background
Inherited retinal degenerations (IRDs) are traditionally considered highly penetrant Mendelian disorders caused by pathogenic variants in specific genes. However, the true population-level penetrance of these variants has been unclear. Using genomic and electronic health record data from the All of Us Research Program and the UK Biobank, researchers sought to quantify how often IRD-associated genotypes translate into clinically diagnosed disease. Understanding penetrance is critical for genetic counseling, variant interpretation, and screening strategies.
Data Highlights
| Parameter | Value |
|---|---|
| All of Us participants screened | 317,964 |
| Individuals with definite IRD-compatible genotypes | 481 |
| Distinct variants identified | 167 across 33 genes |
| Proportion with autosomal dominant variants | 77.8% |
| Proportion with X-linked variants | 15.8% |
| Proportion with homozygous autosomal recessive variants | 6.4% |
| Disease annotation frequency (DAF) range | 9.4% (IRD-specific) to 28.1% (broad screening) |
| UK Biobank participants with shared variants | 482 |
| UK Biobank participants with retinal imaging | 68 |
| Imaging-confirmed IRD-compatible abnormalities | 16.1% definite; up to 27.9% including less definitive |
| Estimated population prevalence of IRD-compatible genotypes | 0.7% to 2.1% |
Key Findings
- Only 9% to 28% of individuals with IRD-associated genotypes had clinical or imaging evidence of retinal disease, indicating incomplete penetrance.
- Variants in genes such as PRPH2, RPGR, and RHO showed significant enrichment for retinal disease codes and imaging abnormalities, while BEST1 and RP1 did not.
- Retinal imaging from the UK Biobank corroborated EHR findings, with 16.1% to 27.9% of variant carriers showing IRD-compatible abnormalities.
- Age, sex, smoking, socioeconomic status, diabetes, and healthcare utilization did not significantly influence penetrance estimates.
- The population prevalence of IRD-compatible genotypes (0.7%–2.1%) is substantially higher than the clinically diagnosed IRD prevalence (~1 in 3,450).
- Findings suggest that IRDs result from interactions between rare high-impact variants and additional genetic or environmental modifiers.
Clinical Implications
These findings highlight the limited positive predictive value of genetic testing for IRDs in asymptomatic individuals, cautioning against routine presymptomatic screening. Clinicians should consider the incomplete penetrance and variable expressivity when counseling patients and interpreting genetic test results. Future research should focus on identifying modifiers that influence disease manifestation to improve risk stratification and management.
Conclusion
The study demonstrates that IRD-associated genetic variants frequently exhibit incomplete penetrance in the general population, underscoring the complex interplay of genetic and environmental factors in disease expression. This challenges previous assumptions and has important implications for genetic testing and clinical care.
Related Resources & Content
- American Journal of Human Genetics 2024 -- Analysis of Real-World Data Challenges Assumptions About IRD Penetrance
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