Pediatr Nephrol (2015) 30:145–152 DOI 10.1007/s00467-014-2889-1
ORIGINAL ARTICLE
Maternal and infantile hypercalcemia caused by vitamin-D-hydroxylase mutations and vitamin D intake Dganit Dinour & Miriam Davidovits & Shraga Aviner & Liat Ganon & Leonid Michael & Dalit Modan-Moses & Iris Vered & Haim Bibi & Yaacov Frishberg & Eli J. Holtzman
Received: 1 January 2014 / Revised: 12 June 2014 / Accepted: 13 June 2014 / Published online: 7 September 2014 # IPNA 2014
Abstract Background Hypercalcemia is caused by many different conditions and may lead to severe complications. Loss-offunction mutations of CYP24A1, encoding vitamin D-24-hydroxylase, have recently been identified in idiopathic infantile hypercalcemia and in adult kidney stone disease. The aim of this study was to investigate the genetics and clinical features of both infantile and maternal hypercalcemia. Methods We studied members of four unrelated Israeli families with hypercalcemia, namely, one woman during pregnancy and after delivery and three infants. Clinical and D. Dinour (*) : L. Ganon : E. J. Holtzman Department of Nephrology and Hypertension, The Chaim Sheba Medical Center, Tel-Hashomer, Ramat-Gan 52621, Israel e-mail: [email protected] M. Davidovits Institute of Pediatric Nephrology, Schneider Children’s Medical Center, Petah Tiqwa, Israel S. Aviner : H. Bibi Department of Pediatrics and the Faculty of Health Sciences, Barzilai Medical Center Campus of the Ben Gurion University of the Negev, Ashkelon, Israel L. Michael : I. Vered Department of Endocrinology, The Chaim Sheba Medical Center, Tel-Hashomer, Ramat-Gan, Israel D. Modan-Moses Pediatric Endocrinology and Diabetes Unit, Chaim Sheba Medical Center, Tel-Hashomer, Ramat-Gan, Israel Y. Frishberg Division of Pediatric Nephrology, Shaare Zedek Medical Center and the Hebrew University School of Medicine, Jerusalem, Israel D. Dinour : L. Ganon : L. Michael : D. Modan-Moses : I. Vered : E. J. Holtzman The Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
biochemical data were obtained from probands’ medical charts. Genomic DNA was isolated from peripheral blood and CYP24A1 was sequenced. Results Typical symptoms of hypercalcemia associated with the intake of recommended doses of vitamin D developed in the infants and pregnant woman. Four different loss-offunction CYP24A1 mutations were identified, two of which are reported here for the first time (p.Trp134Gly and p.Glu315*). The infants from families 1 and 2, respectively, were found to be compound heterozygotes, and the infant from family 3 and the pregnant woman were found to be homozygous. Conclusions This is the first report of maternal hypercalcemia caused by a CYP24A1 mutation, showing that not only infants are at risk for this complication. Our findings emphasize the importance of recognition, genetic diagnosis and proper treatment of this recently identified hypercalcemic disorder in this era of widespread vitamin D supplements. Keywords CYP24A1 . Hypercalciuria . Infantile hypercalcemia . Maternal hypercalcemia . Nephrocalcinosis . Nephrolithiasis . Vitamin D
Introduction Hypercalcemia is caused by many different conditions, including primary hyperparathyroidism, cancer, granulomatous diseases (e.g. sarcoidosis), drugs (e.g. thiazides) and a high intake of calcium and/or vitamin D. In the early 1950s, approximately 200 cases of infants with unexplained hypercalcemia were reported in the UK within only 2 years. These infants presented with failure to thrive, vomiting, dehydration, spikes of fever, nephrocalcinosis and suppressed parathyroid hormone (PTH) levels [1, 2]. Some of the affected children had a complex phenotype that was later
146
identified as the Williams–Beuren syndrome, presenting with supravalvular aortic stenosis, multiple peripheral pulmonary arterial stenoses, ‘elfin face,’ psychomotor and growth delay, characteristic dental malformations and occasionally infantile hypercalcemia (OMIM, #194050). However, most of these infants with hypercalcemia did not have this syndrome, and the condition was considered idiopathic. Although it became evident that vitamin D supplementation plays a role in the pathogenesis of idiopathic infantile hypercalcemia, it took 60 years to identify the genetic defect in vitamin D metabolism that causes this disorder. In 2011, Schlingmann et al. identified loss-of-function mutations in the cytochrome P450 24A1 gene (CYP24A1), which encodes vitamin D-24-hydroxylase, the enzyme that degrades the active form of vitamin D, as the cause of idiopathic infantile hypercalcemia [3]. This finding was later supported by additional studies [4, 5]. Our group and other researchers have since shown that loss-of-function mutations of CYP24A1 may also affect adults, causing long-standing kidney stone disease and nephrocalcinosis that can even lead to chronic kidney injury [6, 7]. During pregnancy and lactation several physiologic adaptations are invoked to supply the required calcium for the offspring. Intestinal calcium absorption more than doubles during pregnancy, and bone resorption occurs to provide calcium for breast milk [8]. Nevertheless, symptomatic hypercalcemia in pregnancy is very rare. We describe here four unrelated subjects who developed symptomatic hypercalcemia due to loss-of-function mutations of CYP24A1. Three infants presented with typical features of “idiopathic infantile hypercalcemia.” The fourth case is a woman with a long-standing kidney stone disease who developed severe hypercalcemia during pregnancy. This is the first report attributing maternal hypercalcemia to a mutated vitamin D-24-hydroxylase. Our findings emphasize the importance of recognition, genetic diagnosis and proper treatment of CYP24A1 defects in infantile as well as maternal hypercalcemia, especially in an era when both expectant mothers and infants are given vitamin D supplements around the world.
Patients and methods Patients We studied four unrelated individuals of Israeli descent who suffered from symptomatic hypercalcemia. the probands were three infants and a woman who developed hypercalcemia during pregnancy and post-partum. Data on clinical symptoms and biochemical tests were obtained from medical charts. The study protocol was approved by the institutional review board of the Chaim Sheba Medical Center, Israel. Informed consent
Pediatr Nephrol (2015) 30:145–152
regarding genetic analysis and medical evaluation was obtained from all of the study subjects. Consent for the infants was given by their parents. Genetic studies Genomic DNA was isolated from peripheral blood cells using the ArchivePure DNA Blood kit (5 PRIME, Gaithersburg, MD) according to the manufacturer’s instructions. The coding sequence and splice-sites of CYP24A1 were amplified by PCR using intronic primers. Primers for CYP24A1 have been described previously [7]. All PCR products were sequenced directly (ABI Prism 3100; Applied Biosystems, Foster City, CA).
Results Clinical findings Family 1 A 5-month-old male infant was hospitalized for repeated vomiting after meals and weight loss during the preceding 2 weeks without fever or diarrhea. The patient was the first child of healthy unrelated parents: a 28-year-old mother of JewishAshkenazi origin and a 34-year-old father of Jewish-Tunisian origin. He was born at term after a normal pregnancy and delivery. Development was normal, and past medical history was unremarkable. He was fed a standard milk formula (Similac; Abbott Laboratories, Abbott Park, IL) and was given the usual vitamin D supplement of 400 IU/day. Physical examination at admission revealed no abnormalities except for a closed anterior fontanel. Blood pressure was 90/ 55 mmHg. Laboratory investigation revealed hypercalcemia, with a serum total calcium level of 13.5 (normal for age 8.8– 11.2) mg/dl and ionized calcium level of 1.8 (normal 1.12– 1.32) mmol/l; the phosphate level was normal (4.7 mg/dl). Kidney function was preserved (serum creatinine 0.2 mg/dl), and levels of serum albumin, glucose, sodium, potassium, magnesium and bicarbonate were within normal range. Urine calcium excretion was markedly elevated; the urinary calcium (mg/dl)/creatinine (mg/dl) ratio was 3.03 (normal for age
ORIGINAL ARTICLE
Maternal and infantile hypercalcemia caused by vitamin-D-hydroxylase mutations and vitamin D intake Dganit Dinour & Miriam Davidovits & Shraga Aviner & Liat Ganon & Leonid Michael & Dalit Modan-Moses & Iris Vered & Haim Bibi & Yaacov Frishberg & Eli J. Holtzman
Received: 1 January 2014 / Revised: 12 June 2014 / Accepted: 13 June 2014 / Published online: 7 September 2014 # IPNA 2014
Abstract Background Hypercalcemia is caused by many different conditions and may lead to severe complications. Loss-offunction mutations of CYP24A1, encoding vitamin D-24-hydroxylase, have recently been identified in idiopathic infantile hypercalcemia and in adult kidney stone disease. The aim of this study was to investigate the genetics and clinical features of both infantile and maternal hypercalcemia. Methods We studied members of four unrelated Israeli families with hypercalcemia, namely, one woman during pregnancy and after delivery and three infants. Clinical and D. Dinour (*) : L. Ganon : E. J. Holtzman Department of Nephrology and Hypertension, The Chaim Sheba Medical Center, Tel-Hashomer, Ramat-Gan 52621, Israel e-mail: [email protected] M. Davidovits Institute of Pediatric Nephrology, Schneider Children’s Medical Center, Petah Tiqwa, Israel S. Aviner : H. Bibi Department of Pediatrics and the Faculty of Health Sciences, Barzilai Medical Center Campus of the Ben Gurion University of the Negev, Ashkelon, Israel L. Michael : I. Vered Department of Endocrinology, The Chaim Sheba Medical Center, Tel-Hashomer, Ramat-Gan, Israel D. Modan-Moses Pediatric Endocrinology and Diabetes Unit, Chaim Sheba Medical Center, Tel-Hashomer, Ramat-Gan, Israel Y. Frishberg Division of Pediatric Nephrology, Shaare Zedek Medical Center and the Hebrew University School of Medicine, Jerusalem, Israel D. Dinour : L. Ganon : L. Michael : D. Modan-Moses : I. Vered : E. J. Holtzman The Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
biochemical data were obtained from probands’ medical charts. Genomic DNA was isolated from peripheral blood and CYP24A1 was sequenced. Results Typical symptoms of hypercalcemia associated with the intake of recommended doses of vitamin D developed in the infants and pregnant woman. Four different loss-offunction CYP24A1 mutations were identified, two of which are reported here for the first time (p.Trp134Gly and p.Glu315*). The infants from families 1 and 2, respectively, were found to be compound heterozygotes, and the infant from family 3 and the pregnant woman were found to be homozygous. Conclusions This is the first report of maternal hypercalcemia caused by a CYP24A1 mutation, showing that not only infants are at risk for this complication. Our findings emphasize the importance of recognition, genetic diagnosis and proper treatment of this recently identified hypercalcemic disorder in this era of widespread vitamin D supplements. Keywords CYP24A1 . Hypercalciuria . Infantile hypercalcemia . Maternal hypercalcemia . Nephrocalcinosis . Nephrolithiasis . Vitamin D
Introduction Hypercalcemia is caused by many different conditions, including primary hyperparathyroidism, cancer, granulomatous diseases (e.g. sarcoidosis), drugs (e.g. thiazides) and a high intake of calcium and/or vitamin D. In the early 1950s, approximately 200 cases of infants with unexplained hypercalcemia were reported in the UK within only 2 years. These infants presented with failure to thrive, vomiting, dehydration, spikes of fever, nephrocalcinosis and suppressed parathyroid hormone (PTH) levels [1, 2]. Some of the affected children had a complex phenotype that was later
146
identified as the Williams–Beuren syndrome, presenting with supravalvular aortic stenosis, multiple peripheral pulmonary arterial stenoses, ‘elfin face,’ psychomotor and growth delay, characteristic dental malformations and occasionally infantile hypercalcemia (OMIM, #194050). However, most of these infants with hypercalcemia did not have this syndrome, and the condition was considered idiopathic. Although it became evident that vitamin D supplementation plays a role in the pathogenesis of idiopathic infantile hypercalcemia, it took 60 years to identify the genetic defect in vitamin D metabolism that causes this disorder. In 2011, Schlingmann et al. identified loss-of-function mutations in the cytochrome P450 24A1 gene (CYP24A1), which encodes vitamin D-24-hydroxylase, the enzyme that degrades the active form of vitamin D, as the cause of idiopathic infantile hypercalcemia [3]. This finding was later supported by additional studies [4, 5]. Our group and other researchers have since shown that loss-of-function mutations of CYP24A1 may also affect adults, causing long-standing kidney stone disease and nephrocalcinosis that can even lead to chronic kidney injury [6, 7]. During pregnancy and lactation several physiologic adaptations are invoked to supply the required calcium for the offspring. Intestinal calcium absorption more than doubles during pregnancy, and bone resorption occurs to provide calcium for breast milk [8]. Nevertheless, symptomatic hypercalcemia in pregnancy is very rare. We describe here four unrelated subjects who developed symptomatic hypercalcemia due to loss-of-function mutations of CYP24A1. Three infants presented with typical features of “idiopathic infantile hypercalcemia.” The fourth case is a woman with a long-standing kidney stone disease who developed severe hypercalcemia during pregnancy. This is the first report attributing maternal hypercalcemia to a mutated vitamin D-24-hydroxylase. Our findings emphasize the importance of recognition, genetic diagnosis and proper treatment of CYP24A1 defects in infantile as well as maternal hypercalcemia, especially in an era when both expectant mothers and infants are given vitamin D supplements around the world.
Patients and methods Patients We studied four unrelated individuals of Israeli descent who suffered from symptomatic hypercalcemia. the probands were three infants and a woman who developed hypercalcemia during pregnancy and post-partum. Data on clinical symptoms and biochemical tests were obtained from medical charts. The study protocol was approved by the institutional review board of the Chaim Sheba Medical Center, Israel. Informed consent
Pediatr Nephrol (2015) 30:145–152
regarding genetic analysis and medical evaluation was obtained from all of the study subjects. Consent for the infants was given by their parents. Genetic studies Genomic DNA was isolated from peripheral blood cells using the ArchivePure DNA Blood kit (5 PRIME, Gaithersburg, MD) according to the manufacturer’s instructions. The coding sequence and splice-sites of CYP24A1 were amplified by PCR using intronic primers. Primers for CYP24A1 have been described previously [7]. All PCR products were sequenced directly (ABI Prism 3100; Applied Biosystems, Foster City, CA).
Results Clinical findings Family 1 A 5-month-old male infant was hospitalized for repeated vomiting after meals and weight loss during the preceding 2 weeks without fever or diarrhea. The patient was the first child of healthy unrelated parents: a 28-year-old mother of JewishAshkenazi origin and a 34-year-old father of Jewish-Tunisian origin. He was born at term after a normal pregnancy and delivery. Development was normal, and past medical history was unremarkable. He was fed a standard milk formula (Similac; Abbott Laboratories, Abbott Park, IL) and was given the usual vitamin D supplement of 400 IU/day. Physical examination at admission revealed no abnormalities except for a closed anterior fontanel. Blood pressure was 90/ 55 mmHg. Laboratory investigation revealed hypercalcemia, with a serum total calcium level of 13.5 (normal for age 8.8– 11.2) mg/dl and ionized calcium level of 1.8 (normal 1.12– 1.32) mmol/l; the phosphate level was normal (4.7 mg/dl). Kidney function was preserved (serum creatinine 0.2 mg/dl), and levels of serum albumin, glucose, sodium, potassium, magnesium and bicarbonate were within normal range. Urine calcium excretion was markedly elevated; the urinary calcium (mg/dl)/creatinine (mg/dl) ratio was 3.03 (normal for age
