Around 100,000 people in the UK are unaware they suffer from high cholesterol which runs in the family, according to a new report.
Cholesterol is not cleared properly from the bloodstream and can cause early heart problems in people with familial hypercholesterolaemia (FH).
Around one in 500 people in the UK inherit FH from a parent.
Now, a new study from the Royal College of Physicians (RCP) points to "inadequacies" in the current system and calls for genetic screening for the close relatives of people with the condition.
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.
But experts found a "major lack" of genetic screening for family members across England and few facilities for screening children.
Only 26% of sites are offering paediatric FH services, although those that exist are of a good standard, according to the review.
Services were assessed against standards laid down by the National Institute for Health and Clinical Excellence (Nice).
Professor Steve Humphries, FH audit project director and director of the centre for cardiovascular genetics at British Heart Foundation laboratories, said: "Although the audit shows that, once identified, patients with FH are being quite well treated in NHS lipid clinics, the lack of commissioned DNA testing and resources for tracing relatives mean that many FH patients remain undiagnosed.
"In the UK I estimate that roughly one undiagnosed FH patient a day suffers a coronary event that could be prevented if funding for these cost-effective measures were available."
Professor Peter Weissberg, medical director at the British Heart Foundation, said: "It's frustrating and unacceptable that families at risk of FH aren't receiving the help and attention they deserve from the health service.
"UK researchers have been 'on the trail' of FH for many years.
"They've tracked down many of the culprit genes, developed tests for them, and gathered robust evidence to prove that screening and treatment is effective.
"They've shown that early identification and treatment of people with the condition could not only prevent people from having a heart attack in their 30s or 40s but could in fact give them back a normal life expectancy.
"It's long overdue that FH services come up to scratch to stop lives across the UK being needlessly lost."Reuse content