Hereditary vitamin D-resistant rickets (HVDRR) owing to a heterozygous mutation in the vitamin D receptor.

Abstract

Hereditary vitamin D-resistant rickets (HVDRR) is a rare autosomal recessive disease caused by mutations in the vitamin D receptor (VDR). Patients exhibit severe rickets and hypocalcemia. Heterozygous parents and siblings appear normal and exhibit no symptoms of the disease. We analyzed the VDR gene of a young girl who exhibited the clinical features of HVDRR without alopecia. The patient had clinical and radiographic features of rickets, hypocalcemia, and elevated serum concentrations of 1,25-dihydroxyvitamin D [1,25(OH)(2)D]. A single heterozygous missense mutation was found in the VDR gene that substituted glutamic acid with alanine at amino acid 420 (E420A). Sequencing of the girl's VDR cDNAs showed that the f/M1 allele contained the E420A mutation, whereas the F/M4 allele was completely normal. The girl's father, who was also heterozygous for the E420A mutation on the f/M1 allele, exhibited minor symptoms of vitamin D resistance. In contrast, the mother had no signs of the disease and had no mutations in her VDR gene. Both the girl and the father's skin fibroblasts showed resistance to 1,25(OH)(2)D(3) by their severely reduced induction of CYP24A1 gene expression. In transactivation assays, the E420A mutant VDR showed dominant-negative activity towards the wild-type VDR. This is the first report that we are aware of describing a patient with HVDRR caused by a single heterozygous missense mutation in the VDR gene. The E420A mutant appears to act in a dominant-negative fashion, silencing the wild-type VDR and resulting in an attenuated response to 1,25(OH)(2)D(3).

• Authors: Peter J Malloy, Yulin Zhou, Jining Wang, Olaf Hiort, David Feldman
• Journal: Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research (J Bone Miner Res) Vol. 26 Issue 11 Pg. 2710-8 (Nov 2011) ISSN: 1523-4681 [Electronic] United States
• PMID: 21812032 (Publication Type: Case Reports, Journal Article, Research Support, N.I.H., Extramural)
• Copyright: Copyright © 2011 American Society for Bone and Mineral Research.

Chemical References

• Mutant Proteins
• Receptors, Calcitriol
• Retinoid X Receptors
• Steroid Hydroxylases
• CYP24A1 protein, human
• Vitamin D3 24-Hydroxylase
• Cyclooxygenase 2
• PTGS2 protein, human
• Calcitriol

Topics

• Adolescent
• Calcitriol (therapeutic use)
• Child
• Child, Preschool
• Cyclooxygenase 2 (genetics)
• DNA Mutational Analysis
• Familial Hypophosphatemic Rickets (diagnostic imaging, drug therapy, enzymology, genetics)
• Female
• Fibroblasts (enzymology, pathology)
• Gene Expression Regulation, Enzymologic
• Genes, Dominant (genetics)
• Heterozygote
• Humans
• Immunoblotting
• Infant
• Mutant Proteins (metabolism)
• Mutation (genetics)
• Protein Multimerization
• Radiography
• Receptors, Calcitriol (genetics)
• Retinoid X Receptors (genetics)
• Steroid Hydroxylases (genetics, metabolism)
• Transcriptional Activation (genetics)
• Vitamin D3 24-Hydroxylase