Familial hypercholesterolemia: epidemiology, genetics, diagnosis, and screening

Familial hypercholesterolaemia (FH) is an autosomal dominant genetic disorder characterized by elevated plasma levels of low-density lipoprotein-cholesterol (LDL-C) and increased risk of premature coronary heart disease. There are two types of FH, namely homozygous and heterozygous FH. FH is most commonly (85%) attributable to mutations in the LDL receptor (LDL-R) gene. Other rare causes are the mutations of genes encoding apolipoprotein B (Apo B), pro-protein convertase subtilisin/ kexin type 9 (PCSK9) and LDL adaptor protein 1 (LDLRAP 1). FH is both underdiagnosed and undertreated, particularly among children. Approximately 20% of patients are diagnosed and, of those, only a small minority receive appropriate treatment. The risk of premature coronary heart disease (CHD) is elevated about 20-fold in untreated FH patients. Early diagnosis of FH enables prompt treatment and prevention of consequent morbidity and mortality from premature CHD. There is no single internationally accepted set of criteria for the clinical diagnosis of FH. The most commonly used are the US (Make Early Diagnosis to Prevent Early Death) MEDPED, the UK (Simon Broome), and the Dutch Lipid Clinic sets of criteria that have been statistically and genetically validated. For early diagnosis and prevention of CVD, testing lipid levels in all first-degree relatives of diagnosed FH patients is necessary. Genetic screening for FH is generally not needed for diagnosis or clinical management, but may be useful when the diagnosis is uncertain.