Background/Aims: Loss-of-function mutations in the CYP24A1 gene, which encodes the vitamin D-24 hydroxylase, have been recognized as a cause of elevated 1,25-dihydroxyvitamin D concentrations, hypercalcemia, hypercalciuria, nephrocalcinosis and nephrolithiasis in infants and adults. As only a case report describing 2 adult patients has been reported in Italian population, we report here the mutation analysis of CYP24A1 gene in an Italian cohort of 12 pediatric and adult patients with idiopathic infantile hypercalcemia (IIH). Methods: We performed mutational screening of CYP24A1 gene in a cohort of 12 Italian patients: 8 children with nephrocalcinosis, hypercalcemia and PTH levels <10 pg/ml and 4 adult patients with nephrolithiasis, mild hypercalcemia and PTH levels <10 pg/ml from 11 unrelated Italian families. Clinical and biochemical data were collected. Genomic DNA was extracted from peripheral blood leucocytes using standard methods, and whole coding sequence of CYP24A1 gene was analysed in all patients and family members by polymerase chain reaction and direct sequencing. The potential pathogenicity of the newly identified missense mutations was evaluated by 3 different in silico approaches (Sorting Intolerant from Tolerant, Polyphen and Mutation Taster) and by comparative analysis in 14 different species using ClustalW software. Results:CYP24A1 bi-allelic mutations were found in 8 individuals from 7 Italian families (7/11; 64%). Overall, 6 different CYP24A1 mutations, including one small deletion (p.Glu143del), 4 missense mutations (p.Leu148Pro; p.Arg396Trp; p.Pro503Leu; p.Glu383Gln) and one nonsense mutation (p.Tyr220*) were identified. Two out of 6 mutations (p.Tyr220* and p.Pro503Leu) were not previously described. Moreover, a new CYP24A1 variant was identified by genetic screening of asymptomatic controls. Conclusion: To the best of our knowledge, this is the first report of a CYP24A1 molecular analysis performed in an Italian cohort of adult and pediatric Italian patients. This study (1) confirms that CYP24A1 plays a causal role in some but not all cases of IIH (64%); (2) expands the spectrum of known CYP24A1 pathogenic mutations; (3) describes 2 hotspots detected in 50% of all Italian cases; and (4) emphasizes the importance of recognition and genetic diagnosis of CYP24A1 defects in infantile as well as adult hypercalcemia.

1.
Jones G, Prosser DE, Kaufmann M: 25-Hydroxyvitamin D-24-hydroxylase (CYP24A1): its important role in the degradation of vitamin D. Arch Biochem Biophys 2012;523:9-18.
2.
Annalora AJ, Goodin DB, Hong WX, Zhang Q, Johnson EF, Stout CD: Crystal structure of CYP24A1, a mitochondrial cytochrome P450 involved in vitamin D metabolism. J Mol Biol 2010;396:441-451.
3.
Wang TJ, Zhang F, Richards JB, et al: Common genetic determinants of vitamin D insufficiency: a genome-wide association study. Lancet 2010;376:180-188.
4.
Ahn J, Yu K, Stolzenberg-Solomon R, Simon KC, McCullough ML, Gallicchio L, Jacobs EJ, Ascherio A, Helzlsouer K, Jacobs KB, Li Q, Weinstein SJ, Purdue M, Virtamo J, Horst R, Wheeler W, Chanock S, Hunter DJ, Hayes RB, Kraft P, Albanes D: Genome-wide association study of circulating vitamin D levels. Hum Mol Genet 2010;19:2739-2745.
5.
St-Arnaud R: Targeted inactivation of vitamin D hydroxylases in mice. Bone 1999;25:127-129.
6.
Masuda S, Byford V, Arabian A, Sakai Y, Demay MB, St-Arnaud R, Jones G: Altered pharmacokinetics of 1alpha,25-dihydroxyvitamin D3 and 25-hydroxyvitamin D3 in the blood and tissues of the 25-hydroxyvitamin D-24-hydroxylase (Cyp24a1) null mouse. Endocrinology 2005;146:825-834.
7.
Schlingmann KP, Kaufmann M, Weber S, Irwin A, Goos C, John U, Misselwitz J, Klaus G, Kuwertz-Bröking E, Fehrenbach H, Wingen AM, Güran T, Hoenderop JG, Bindels RJ, Prosser DE, Jones G, Konrad M: Mutations in CYP24A1 and idiopathic infantile hypercalcemia. N Engl J Med 2011;365:410-421.
8.
Nesterova G, Malicdan MC, Yasuda K, Sakaki T, Vilboux T, Ciccone C, Horst R, Huang Y, Golas G, Introne W, Huizing M, Adams D, Boerkoel CF, Collins MT, Gahl WA: 1,25-(OH)2D-24 hydroxylase (CYP24A1) deficiency as a cause of nephrolithiasis. Clin J Am Soc Nephrol 2013;8:649-657.
9.
Dauber A, Nguyen TT, Sochett E, Cole DE, Horst R, Abrams SA, Carpenter TO, Hirschhorn JN: Genetic defect in CYP24A1, the vitamin D 24-hydroxylase gene, in a patient with severe infantile hypercalcemia. J Clin Endocrinol Metab 2012;97:E268-E274.
10.
Fencl F, Bláhová K, Schlingmann KP, Konrad M, Seeman T: Severe hypercalcemic crisis in an infant with idiopathic infantile hypercalcemia caused by mutation in CYP24A1 gene. Eur J Pediatr 2013;172:45-49.
11.
Dinour D, Davidovits M, Aviner S, Ganon L, Michael L, Modan-Moses D, Vered I, Bibi H, Frishberg Y, Holtzman EJ: Maternal and infantile hypercalcemia caused by vitamin-D-hydroxylase mutations and vitamin D intake. Pediatr Nephrol 2015;30:145-152.
12.
Castanet M, Mallet E, Kottler ML: Lightwood syndrome revisited with a novel mutation in CYP24 and vitamin D supplement recommendations. J Pediatr 2013;163:1208-1210.
13.
Streeten EA, Zarbalian K, Damcott CM: CYP24A1 mutations in idiopathic infantile hypercalcemia. N Engl J Med 2011;365:1741-1742; author reply 1742-1743.
14.
Dinour D, Beckerman P, Ganon L, Tordjman K, Eisenstein Z, Holtzman EJ: Loss-of-function mutations of CYP24A1, the vitamin D 24-hydroxylase gene, cause long-standing hypercalciuric nephrolithiasis and nephrocalcinosis. J Urol 2013;190:552-557.
15.
Tebben PJ, Milliner DS, Horst RL, Harris PC, Singh RJ, Wu Y, Foreman JW, Chelminski PR, Kumar R: Hypercalcemia, hypercalciuria, and elevated calcitriol concentrations with autosomal dominant transmission due to CYP24A1 mutations: effects of ketoconazole therapy. J Clin Endocrinol Metab 2012;97:E423-E427.
16.
Meusburger E, Mündlein A, Zitt E, Obermayer-Pietsch B, Kotzot D, Lhotta K: Medullary nephrocalcinosis in an adult patient with idiopathic infantile hypercalcaemia and a novel CYP24A1 mutation. Clin Kidney J 2013;6:211-215.
17.
Colussi G, Ganon L, Penco S, De Ferrari ME, Ravera F, Querques M, Primignani P, Holtzman EJ, Dinour D: Chronic hypercalcaemia from inactivating mutations of vitamin D 24-hydroxylase (CYP24A1): implications for mineral metabolism changes in chronic renal failure. Nephrol Dial Transplant 2014;29:636-643.
18.
Figueres ML, Linglart A, Bienaime F, Allain-Launay E, Roussey-Kessler G, Ryckewaert A, Kottler ML, Hourmant M: Kidney function and influence of sunlight exposure in patients with impaired 24-hydroxylation of vitamin D due to CYP24A1 mutations. Am J Kidney Dis 2015;65:122-126.
19.
Molin A, Baudoin R, Kaufmann M, Souberbielle JC, Ryckewaert A, Vantyghem MC, Eckart P, Bacchetta J, Deschenes G, Kesler-Roussey G, Coudray N, Richard N, Wraich M, Bonafiglia Q, Tiulpakov A, Jones G, Kottler ML: CYP24A1 mutations in a cohort of hypercalcemic patients: evidence for a recessive trait. J Clin Endocrinol Metab 2015;100:E1343-E1352.
20.
Schlingmann KP, Ruminska J, Kaufmann M, Dursun I, Patti M, Kranz B, Pronicka E, Ciara E, Akcay T, Bulus D, Cornelissen EA, Gawlik A, Sikora P, Patzer L, Galiano M, Boyadzhiev V, Dumic M, Vivante A, Kleta R, Dekel B, Levtchenko E, Bindels RJ, Rust S, Forster IC, Hernando N, Jones G, Wagner CA, Konrad M: Autosomal-recessive mutations in SLC34A1 encoding sodium-phosphate cotransporter 2A cause idiopathic infantile hypercalcemia. J Am Soc Nephrol 2015;27:604-614.
21.
Braun DA, Lawson JA, Gee HY, Halbritter J, Shril S, Tan W, Stein D, Wassner AJ, Ferguson MA, Gucev Z, Fisher B, Spaneas L, Varner J, Sayer JA, Milosevic D, Baum M, Tasic V, Hildebrandt F: Prevalence of monogenic causes in pediatric patients with nephrolithiasis or nephrocalcinosis. Clin J Am Soc Nephrol 2016;11:664-672.
22.
Vijayakumar M, Nageswaran P, Tirukalathi OM, Sudha E, Priyadarshini S: Descriptive study of clinical profile and benefit of therapy in childhood hypercalciuria. Int J Nephrol Renovasc Dis 2014;7:69-73.
23.
Lightwood R: Idiopathic hypercalcaemia with failure to thrive: nephrocalcinosis. Proc R Soc Med 1952;45:40.
24.
Huang J, Coman D, McTaggart SJ, Burke JR: Long-term follow-up of patients with idiopathic infantile hypercalcaemia. Pediatr Nephrol 2006;21:1676-1680.
25.
Gartner LM, Greer FR; Section on Breastfeeding and Committee on Nutrition. American Academy of Pediatrics: Prevention of rickets and vitamin D deficiency: new guidelines for vitamin D intake. Pediatrics 2003;111(4 pt 1):908-910.
26.
Wagner CL, Greer FR; American Academy of Pediatrics Section on Breastfeeding; American Academy of Pediatrics Committee on Nutrition: Prevention of rickets and vitamin D deficiency in infants, children, and adolescents. Pediatrics 2008;122:1142-1152.
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