Table 1. Forms of manifestation, prevalence rates, and clinical characteristics of familial hypercholesterolemia (autosomal dominant hypercholesterolemia^*1).

Manifestation	Prevalence*2	Typical LDL cholesterol concentrations	Clinical characteristics
Heterozygous	1 in 500	190 to 450 mg/dL(4.9 to 11.6 mmol/L)	Familial clustering, tendon xanthomas of the extensor tendons of the joints of the fingers and Achilles tendons, xanthelasmata, arcus corneae, arthritis, manifestations of cardiovascular disease from early adulthood onwards possible
Homozygous or combined heterozygous	1 in 1000000	400 to >1000 mg/dL (10 to >26 mmol/L) and above possible	Familial clustering, interdigital planar xanthomas, cutaneous xanthomas, tendon xanthomas of the extensor tendons of the joints of the fingers and Achilles tendons, xanthelasmata, arcus corneae, arthritis, severe cardiovascular atherosclerosis, and atherosclerosis of the aortic valve in early childhood possible

^*1Umbrella term for hypercholesterolemia caused by LDL receptor mutations (85 to 90%), apolipoprotein B-100 mutations (2 to 7%), or PSCK9 (proprotein convertase subtilisin/kexin type 9) gain-of-function mutations (less than 3%). Mutations of LDL receptor adapter protein 1 (LDLRAP1) are extremely rare; these cause autosomal recessive hypercholesterolemia (ARH) and lead to a phenotype corresponding to familial hypercholesterolemia.

^*2Prevalence figures are based on assumptions made for Western populations. The prevalence rate of 1 in 500 is probably also an underestimate for Germany. Higher prevalence rates are found in some populations, e.g. 1 in 270 for HeFH in specific Canadian populations (11); a particularly high prevalence rate of 1 in 72 is found in South Africa (12). A HoFH prevalence rate of 1 in 860 000 is reported for Germany (e48), 1 in 640 000 for the Netherlands (13), 1 in 275 000 for Canada (11), and as high as 1 in 30 000 for South Africa (12).