In populations with ahigh level of blood relationship, the frequency of incompleteosteogenesis is higher, for example, among African Americans in the United States of America, the frequency of themutant variant in the P3H1 gene (previously called LEPRE1encoding shedding 3-hydroxylase 1) is about 1 in 240 people.Homozygosity for this so-called West African allele accountsfor 25 % of all cases of incomplete lethal osteogenesis in thispopulation, which may be clinically erroneously classifiedas type II OI. Here, P3H1 is linked to osteogenesis imperfecta.