Sitosterolaemia in Switzerland: molecular genetics links the US Amish‐Mennonites to their European roots

Sitosterolaemia is a rare autosomal recessive disease characterized by increased intestinal absorption of plant sterols, decreased hepatic excretion into bile and elevated concentrations in plasma phytosterols. Homozygous or compound heterozygous loss of function mutations in either of the ATP‐binding cassette (ABC) proteins ABCG5 and ABCG8 explain the increased absorption of plant sterols. Here we report a Swiss index patient with sitosterolaemia, who presented with the classical symptoms of xanthomas, but also had mitral and aortic valvular heart disease. Her management over the last 20 years included a novel therapeutic approach of high‐dose cholesterol feeding that was semi‐effective. Mutational and extended haplotype analyses showed that our patient shared this haplotype with that of the Amish‐Mennonite sitosterolaemia patients, indicating they are related ancestrally.