Inherited malabsorption of cobalamin (Cbl) causes hematological and neurological abnormalities that can be fatal. Three genes have been implicated in Cbl malabsorption; yet, only about 10% of ~400-500 reported cases have been molecularly studied to date. Recessive mutations in CUBN or AMN cause Imerslund-Gräsbeck Syndrome (IGS), while recessive mutations in GIF cause Intrinsic Factor Deficiency (IFD). IGS and IFD differ in that IGS usually presents with proteinuria, which is not observed in IFD. The genetic heterogeneity and numerous differential diagnoses make clinical assessment difficult.

The number of clinically available genetic tests for heritable cardiovascular diseases has recently increased because of novel gene discoveries and advancements in DNA sequencing technologies. The purpose of this review is to provide up-to-date genetic testing information and guidance on how to incorporate genetic testing into cardiovascular medicine. Heritable cardiovascular conditions display vast genetic heterogeneity, genetic overlap between phenotypes, incomplete penetrance and variable expressivity, and are associated with risk for sudden cardiac death, making the practice of cardiovascular genetic medicine a great responsibility. Multigene testing panels now exist for many cardiovascular conditions, and test utility has recently been augmented by population-based genomic sequence datasets. Large amounts of DNA sequence data necessitate rigorous interpretation of this probabilistic information. Timely practice guidelines and expert statements have been published. To fully realize the benefits of clinical genetic testing in cardiovascular medicine, clinicians must implement several components including judicious genetic testing, pretest and posttest genetic counseling, interpretation and application of genetic test results, and cascade family genetic testing and clinical screening. Components important to the proper integration of cardiovascular genetic medicine are offered.

Background: Familial hypercholesterolemia (FH) is the most common cardiovascular genetic disorder and, if left untreated, is associated with increased risk of premature atherosclerotic cardiovascular disease, the leading cause of preventable death in the United States. Although FH is common, fatal, and treatable, it is underdiagnosed and undertreated due to a lack of systematic methods to identify individuals with FH and limited uptake of cascade testing. Methods and Results: This mixed-method, multi-stage study will optimize, test, and implement innovative approaches for both FH identification and cascade testing in 3 aims. To improve identification of individuals with FH, in Aim 1, we will compare and refine automated phenotype-based and genomic approaches to identify individuals likely to have FH. To improve cascade testing uptake for at-risk individuals, in Aim 2, we will use a patient-centered design thinking process to optimize and develop novel, active family communication methods. Using a prospective, observational pragmatic trial, we will assess uptake and effectiveness of each family communication method on cascade testing. Guided by an implementation science framework, in Aim 3, we will develop a comprehensive guide to identify individuals with FH. Using the Conceptual Model for Implementation Research, we will evaluate implementation outcomes including feasibility, acceptability, and perceived sustainability as well as health outcomes related to the optimized methods and tools developed in Aims 1 and 2. Conclusions: Data generated from this study will address barriers and gaps in care related to underdiagnosis of FH by developing and optimizing tools to improve FH identification and cascade testing.

Cardiovascular Cascade Genetic Testing: Exploring the Role of Direct Contact and Technology