Can genetic testing help in the management of dyslipidaemias?

The advantages and pitfalls of genetic analysis in the diagnosis and management of lipid disorders

The increasing affordability of and access to next-generation DNA sequencing has increased the feasibility of incorporating genetic analysis into the diagnostic pathway for dyslipidaemia. But should genetic diagnosis be used routinely? DNA testing for any medical condition has potential benefits and pitfalls. For dyslipidaemias, the overall balance of advantages versus drawbacks differs according to the main lipid disturbance. For instance, some patients with severely elevated low-density lipoprotein cholesterol levels have a monogenic disorder, namely heterozygous familial hypercholesterolaemia. In these patients, DNA diagnosis can be definitive, in turn yielding several benefits for patient care that tend to outweigh any potential disadvantages. In contrast, hypertriglyceridaemia is almost always a polygenic condition without a discrete monogenic basis, except for ultrarare monogenic familial chylomicronaemia syndrome. Genetic testing in patients with hypertriglyceridaemia is therefore predominantly non-definitive and evidence for benefit is presently lacking. Here we consider advantages and limitations of genetic testing in dyslipidaemias.

Genetic testing in dyslipidaemia: An approach based on clinical experience

We have used DNA sequencing in our lipid clinic for >20 years. Dyslipidaemia is typically ascertained biochemically. For moderate deviations in the lipid profile, the etiology is often a combination of a polygenic susceptibility component plus secondary non-genetic factors. For severe dyslipidaemia, a monogenic etiology is more likely, although a discrete single-gene cause is frequently not found. A severe phenotype can also result from strong polygenic predisposition that is aggravated by secondary factors. A young age of onset plus a family history of dyslipidaemia or atherosclerotic cardiovascular disease can suggest a monogenic etiology. With severe dyslipidaemia, clinical examination focuses on detecting manifestations of monogenic syndromic conditions. For all patients with dyslipidaemia, secondary causes must be ruled out. Here we describe an experience-based practical approach to genetic testing of patients with severe deviations of low-density lipoprotein, triglycerides, high-density lipoprotein and also combined hyperlipidaemia and dysbetalipoproteinemia.

Monogenic Versus Polygenic Forms of Hypercholesterolemia and Cardiovascular Risk: Are There Any Differences?

PURPOSE OF REVIEW

Common DNA variants with small effects work together to create susceptibility to polygenic hypercholesterolemia. Some clinicians wonder whether patients with polygenic hypercholesterolemia have less severe clinical features compared to patients with monogenic familial hypercholesterolemia (FH) caused by rare deleterious variants.

RECENT FINDINGS

Studies performed in cohorts of patients with both monogenic and polygenic hypercholesterolemia have assessed lipid levels, non-invasive markers of atherosclerosis, and clinical end points, including major adverse cardiovascular events. The totality of data suggests a gradient across genotypes. Specifically, individuals with polygenic hypercholesterolemia have deleterious phenotypes that are intermediate in severity between those in patients with monogenic hypercholesterolemia and in control subjects. Although clinical variables in patients with polygenic hypercholesterolemia are less severe than in those with monogenic hypercholesterolemia, cardiovascular risk is still very high in these patients compared to controls. Patients with polygenic hypercholesterolemia must be treated assertively.

The genetic counselor's role in management of patients with dyslipidemia

PURPOSE OF REVIEW

The role of genetic testing in diagnosis and management of dyslipidemias continues to grow. Consequently, it is increasingly important for patients to have access to clinicians who have expertise in medical genetics and the psychological implications related to this type of testing. Often a lipidologist has had limited training in this regard, and this review explores the role of the genetic counselor to fill this gap.

RECENT FINDINGS

Genetic counselors are key members of the healthcare team, and their specialized training in medical genetics and counseling allows them to fill this professional knowledge gap within the lipid clinic.

SUMMARY

With the continued emphasis on precision medicine, the utility of genetic testing for dyslipidemias will continue to grow. This will in turn increase the demand for provider expertise in medical genetics and counseling around these complex issues. Integrating a genetic counselor within the lipid clinic provides an ideal management scenario providing patients and families with access to not only medical information but also emotional support regarding their hereditary condition.