Clinical and biochemical phenotypes of adults with monoallelic and biallelic CYP24A1 mutations: evidence of gene dose effect

D. T. O’Keeffe, P. J. Tebben, R. Kumar, R. J. Singh, Y. Wu, R. A. Wermers

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

Summary: Mutations of the CYP24A1 gene can result in hypercalcemia, hyerpercalciuria, and nephrolithiasis, but disease severity is variable. Clinical and biochemical phenotypes were correlated with gene sequence information in a family with two CYP24A1 mutations. A gene dose effect was apparent with monoallelic mutations demonstrating milder disease manifestations than biallelic mutations. Introduction: The objective was to examine the spectrum of clinical and biochemical phenotypes in a family with monoallelic and biallelic mutations of CYP24A1 after identification of the proband with two mutations of the CYP24A1 gene: (A) p.R396W and (B) E143del-Het. Methods: Clinical and biochemical phenotypes were correlated with CYP24A1 sequence information in the proband and four siblings, a daughter, and two nieces of the proband. The subjects’ medical histories were evaluated, and measurement of serum minerals, vitamin D metabolites, PTH, bone turnover markers, and urinary calcium and sequencing of the CYP24A1 gene were performed. Results: The proband had nephrolithiasis, osteopenia, hypercalcemia, hypercalciuria, elevated serum 1,25(OH)2D, undetectable 24,25(OH)2D, and inappropriately low PTH concentrations. Two subjects with biallelic (A/B) mutations had nephrolithiasis, marked hypercalciuria (583 ± 127 mg/24 h, mean ± SD), compared with five subjects with monoallelic mutations (A or B) with a urine calcium of 265 ± 85 mg/24 h. Two subjects with monoallelic mutations had nephrolithiasis and one had non-PTH dependent hypercalcemia. Five subjects had high 1,25(OH)2D measurements, including three with monoallelic mutations. The 25OHD/24,25(OH)2D ratio, in subjects with biallelic mutations was 291 versus 19.8 in the subjects with monoallelic mutations. Conclusions: In this family, adults with CYP24A1 mutations a gene dose effect is apparent: subjects with biallelic, compound heterozygous mutations (A/B) have a more severe clinical and biochemical phenotype, whereas, subjects with monoallelic mutations demonstrate milder disease manifestations which are not easily characterized through biochemical assessment.

Original languageEnglish (US)
Pages (from-to)3121-3125
Number of pages5
JournalOsteoporosis International
Volume27
Issue number10
DOIs
StatePublished - Oct 1 2016

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Keywords

  • CYP24A1
  • Genetic
  • Hypercalcemia
  • Nephrolithiasis
  • Vitamin D

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism

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