Chronic Thromboembolic Pulmonary Hypertension Cases Cluster in Families

Chronic thromboembolic pulmonary hypertension (CTEPH) is a serious sequela of pulmonary embolism (PE) and occurs in about 3% of acute PE survivors. Common inherited thrombophilias, including the Factor V Leiden mutation, are not associated with increased risk of CTEPH, even though they increase the risk for VTE. Whether other inherited genetic factors contribute to the risk of developing CTEPH remains unknown. Familial clustering of a disease can indicate inherited genetic risk for that disease. In this study, the Utah Population Database (UPDB), a unique genealogy resource, was used to assess whether CTEPH cases cluster in families. Prevalent CTEPH patients in Utah were identified and were then matched to control subjects. Using the UPDB, the Genealogical Index of Familiality (a statistical measure of relatedness of individuals with a given phenotype) was calculated. The UPDB was also used to calculate the relative risk of CTEPH and VTE in the family members of patients with CTEPH. This study found that Utah patients with CTEPH are significantly more related than would be expected by chance, with both close and distant relationships identified. We also found that the relative risk of VTE was significantly increased among first-degree relatives of CTEPH probands. The study data suggest that heritable genetic factors influence an individual’s risk of developing CTEPH, providing the strongest evidence to date for a genetic contribution to CTEPH risk. Although our data suggest that these inherited genetic factors likely also increase the risk for VTE, they are likely to be distinct from the common inherited thrombophilias.