Background: The renal form of pseudohypoaldosteronism type 1 (PHA1) is a rare disease characterized by congenital mineralocorticoid resistance of the kidney. Twenty-two different loss-of-function mutations in the mineralocorticoid receptor gene have been described in families with PHA1. These mutations were not recurrent and resulted in a large phenotypic variability.
Objective: The objective of this study is to analyze the recurrence of an inactivating mutation in the mineralocorticoid receptor gene in unrelated families with autosomal dominant PHA1.
Patients: Seventeen members from three unrelated families with autosomal dominant PHA1 were studied, including 11 affected patients with variable clinical manifestations. Fifty healthy subjects were used as controls.
Methods: Genomic DNA was extracted, and the entire coding region of the mineralocorticoid receptor gene was submitted to automatic sequencing. Four dinucleotide microsatellite markers spanning a region of 3.2 cM in the human mineralocorticoid receptor gene locus, and two intragenic polymorphisms were used for haplotype analysis.
Results: A heterozygous point mutation at codon 947 (c.2839C>T) changing arginine to stop codon (R947X) was found in the three families. Different haplotypes segregated with the R947X mutation in each family, demonstrating the absence of a founder effect for this mutation.
Conclusion: Codon 947 of the mineralocorticoid receptor is the first mutational hot spot for autosomal dominant PHA1.