The role of rare variants in TTR as causative mutations in Hypertrophic Cardiomyopathy is described below. By comparing the frequency of TTR variants in large HCM clinical cohorts to the background population rate in the ExAC database, the proportion of HCM patients with pathogenic mutations in TTR can be estimated, as well as the likelihood that a rare (population allele frequency <0.0001) TTR variant identified in a HCM patient is disease-causing. Summary data for different variant classes (all protein-altering variants, loss of function truncating variants and non-truncating variants) is highlighted - see the table below for full details of this analysis.
Excess of TTR variants in HCM: 0.18% (p=0.2264)
Based on an analysis of all rare protein-altering variants (MAF<0.0001 in ExAC) in TTR found in 632 HCM samples sequenced by OMGL and LMM and in reference samples of the ExAC population database.
| All Vars | Truncating | Non-Truncating | |
|---|---|---|---|
| Excess in HCM | 0.18% p=0.2264 |
0.00% p=1.0000 |
0.18% p=0.2150 |
| Etiological fraction | 0.56 0.00 - 0.88 |
- | 0.57 0.00 - 0.89 |
| Odds Ratio | 2.26 0.27 - 8.45 |
0.00 0.00 - 123.03 |
2.34 0.28 - 8.77 |
The Etiological Fraction (EF) is the proportion of affected carriers where the variant caused HCM. The Odds Ratio (OR) describes the odds of having a rare variant in the patient cohort to the odds in the ExAC cohort. Fisher's exact test p-values are displayed for case excess, 95% confidence intervals for EFs and ORs.
| Source | Samples Tested | Variant Type | Variants detected | Frequency in HCM |
Frequency in ExAC | Case Excess in HCM |
|---|---|---|---|---|---|---|
| LMM2 | 632 | All | 2 | 0.00316 | 0.00140 | 0.00176 |
| Truncating | 0 | 0.00000 | 0.00004 | -0.00004 | ||
| Non-Truncating | 2 | 0.00316 | 0.00136 | 0.00180 |
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