A Novel Variant Heterozygote CYP24A1 Gene Mutation: A Rare Cause of Adult Onset Recurrent Nephrolithiasis

Presentation Number: SAT 313
Date of Presentation: April 1st, 2017

Grace Y Kim*, Joanna Khatib, Jamila Benmoussa and Hassan Shawa
Albany Medical College, Albany, NY

Abstract

Introduction: CYP24A1 homozygous gene mutation is a well known cause of infantile hypercalcemia and adult onset nephrocalcinosis. A mutation in this gene causes the loss of function of 24 hydroxylase enzyme that is essential for the excretion of vitamin D metabolites. We describe a rare case of an adult patient with recurrent nephrolithiasis carrying a heterozygous mutation of the CYP24A1 gene.

Case presentation: A 35 year old man presented with recurrent nephrolithiasis that began in his adulthood. Biochemical work up was remarkable for hypercalcemia (10.6 mg/dl, nl. 8-6-10.3), hypercalciuria (24-hr urine calcium 421 mg/24hr, nl < 300), high 1,25-dihydroxyvitamin D (160 pg/mL, nl. 10.0 – 75.0) and low parathyroid hormone level (12.4 pg/mL, nl. 14 –72). 25-hydroxyvitamin D was 20.4 pg/ml (nl. 21–50). He had no known history of hypercalcemia during childhood. Patient denies the use of vitamin D supplement. Extensive workup for granulomatous, infectious, autoimmune diseases and malignancies were negative. Genetic testing revealed a double heterozygous mutation in the CYP24A1 gene.

Conclusion: This case illustrates that heterozygous mutation of CYP24A1 gene can precipitate adult onset recurrent nephrolithiasis. Performing the genetic testing for CYP24A1 gene mutations in adults with recurrent nephrolithiasis should be considered especially if it is associated with non PTH-mediated hypercalcemia and/or hypercalciuria even without history of hypercalcemia during childhood.

 

Nothing to Disclose: GYK, JK, JB, HS