Familial hypercholesterolaemia (FH) is a well-defined but underdiagnosed dyslipidaemia occurring in 1:500 persons. We report a case where an 18-year-old woman with an untreated FH dies a sudden cardiac death due to acute myocardial infarction. In patients with FH atherosclerotic manifestations are common at a young age and FH should always be suspected in patients with P-low-density lipoprotein cholesterol level above 5 mmol/l (4 mmol/l for persons < 16 years of age). Patients with FH should be referred to specialized units so that family members with FH systematically are identified.