Prevalence of mild apparent mineralocorticoid excess in Mennonites

We have studied an unusual patient with mild low-renin hypertension due to a homozygous mutation in the HSD11B2 gene (PNAS 95:10200-10205, 1998). The patient came from an inbred Mennonite family, and though the mutation identified her as an AME patient, she had a normal birth weight and did not demonstrate the typical features of AME, such as hypokalemic alkalosis, low birth weight, failure to thrive, poor growth, and in many cases nephrocalcinosis. Biochemically, typical patients with AME have abnormal cortisol metabolites and an exceedingly diminished ability to convert [11-3H]cortisol to cortisone. In this patient with mild AME, the conversion of cortisol to cortisone was 58% compared to 0 to 6% in typical AME patients, while the normal conversion is 90 to 95%. Molecular analysis of the HSD11B2 gene of this patient showed a homozygous mutation in codon 227 (P227L). We studied this Mennonite population for the prevalence of the P227L mutation. Our hypothesis was that this mild form of AME would be prevalent in the somewhat inbred Mennonite population to which the patient belongs. Our proposed study was 1) to determine if there are other cases of this mild form of AME, and 2) to establish the heterozygote frequency of the mutation in the Mennonites.

We did not detect any additional cases of mild AME. We detected 15 carriers of the P227L mutation out of 445 Mennonites, resulting in a heterozygote frequency of 0.03.

Since this is an inbred population, the chance of two heterozygotes marrying would be 0.001, which is 1 in 1000 people. This population is known to have large families and therefore the possibility of having an affected child is high. The population consists of 2000 members and we have discovered one affected patient. Thus, there might be one other patient in this population.