There are about 100,000 sufferers of high blood pressure in the UK who do not know they have inherited the condition, a report has revealed.
Cholesterol does not get out of the bloodstream properly and can trigger early heart problems in people with familial hypercholesterolaemia (FH).
FH is inherited from a parent by one in 500 people in the UK.
Close relatives of people with the condition should receive genetic screening, according to a new study from the Royal College of Physicians (RCP), which highlighted "inadequacies" in the current system.
If left untreated, about half of men with the condition will have developed heart disease by the age of 55, and roughly a third of women by the age of 60.
Half of their first-degree relatives - brothers, sisters and children - will also have FH but are frequently undiagnosed, putting them at risk of early death.
Treating these people with cholesterol-lowering drugs (statins) and encouraging healthy diets and plenty of exercise could lead to normal life expectancy, according to the report.
In the latest audit of more than 2,324 adults and 147 children, researchers found that people who have been identified with the illness receive good NHS care.
The audit was carried out at 122 sites across the UK and was funded by the RCP, British Heart Foundation, Heart UK and the Cardiac Network Co-ordinating Group, Wales.
"If mother and father both have high blood pressure, on medication and blood pressure is within normal now. What guidelines are there to inform them when their children should have their blood pressure check or cholesterol check done" - Kim Low, Surrey
"Yes it all very well informing people of this but when they attend their local GP for a cholesterol test they are turned away" - Angela Johnson, Newcastle