title: A Case of "Late-Onset" Idiopathic Infantile Hypercalcemia Secondary to Mutations in the CYP24A1 Gene.
abstract: OBJECTIVE
  Mutations in the 24-hydroxylase gene, CYP24A1, have recently been reported to cause idiopathic infantile hypercalcemia (IIH), a rare disease presenting in the first year of life that is characterized by increased sensitivity to vitamin D, leading to severe symptomatic hypercalcemia.
  
  
  METHODS
  We present a case report and review the relevant literature.
  
  
  RESULTS
  A 24-year-old Caucasian man presented with repetitive signs of nephrolithiasis since the age of 18 years, hypercalciuria (17.1 mmol/24 h), slightly elevated serum calcium concentration (2.64 mmol/L), and inappropriately high levels of 1,25-dihydroxyvitamin D (101 pg/mL) in combination with suppressed levels of circulating parathormone (7.9 pg/mL). Exogenous vitamin D intoxication as well as granulomatous disease or malignancy were excluded. Genetic analysis revealed a loss-of-function mutation in CYP24A1. Of note, our patient denied any prior clinical signs of impaired calcium homeostasis during childhood.
  
  
  CONCLUSIONS
  Here, we describe the exceptional case of a patient with hypercalciuria and recurrent nephrolithiasis secondary to mutations in CYP24A1, without any signs of IIH in childhood, indicating that the phenotypic spectrum includes mild "late-onset" disease that becomes symptomatic in adolescence. Therefore, reduced CYP24A1 activity should be considered as a possible reason for recurrent nephrolithiasis in adults.
authors: Department of Internal Medicine III, Division of Endocrinology and Metabolism, Medical University of Vienna, Vienna, Austria.
authors: Peter
authors: P
authors: Wolf
authors: Department of Pediatrics, Medical University of Vienna, Vienna, Austria.
authors: Thomas
authors: T
authors: Müller-Sacherer
authors: Department of Internal Medicine III, Division of Endocrinology and Metabolism, Medical University of Vienna, Vienna, Austria.
authors: Sabina
authors: S
authors: Baumgartner-Parzer
authors: Department of Internal Medicine III, Division of Endocrinology and Metabolism, Medical University of Vienna, Vienna, Austria.
authors: Yvonne
authors: Y
authors: Winhofer
authors: Division of Endocrinology and Metabolism, Health Center of the Regional Medical Insurance Company of Vienna, Vienna, Austria.
authors: Judit
authors: J
authors: Kroo
authors: Department of Internal Medicine III, Division of Endocrinology and Metabolism, Medical University of Vienna, Vienna, Austria.
authors: Alois
authors: A
authors: Gessl
authors: Department of Internal Medicine III, Division of Endocrinology and Metabolism, Medical University of Vienna, Vienna, Austria.
authors: Anton
authors: A
authors: Luger
authors: Department of Internal Medicine III, Division of Endocrinology and Metabolism, Medical University of Vienna, Vienna, Austria.
authors: Michael
authors: M
authors: Krebs