Clinic of Pediatric Endocrinology, Dr. Sami Ulus Obstetrics and Gynecology and Pediatrics Training and Research Hospital, Ankara, Turkey,
Clinic of Pediatric Endocrinology, Dr. Sami Ulus Obstetrics and Gynecology and Pediatrics Training and Research Hospital, Ankara, Turkey.
Horm Res Paediatr. 2019;91(4):278-284. doi: 10.1159/000492899. Epub 2018 Sep 18.
Under physiological conditions, proximal tubular phosphate reabsorption via NaPi-IIa (and NaPi-IIc) ensures the maintenance of phosphate homeostasis. Impairment of NaPi-IIa, encoded by SLC34A1, is associated with various overlapping clinical syndromes, including hypophosphatemic nephrolithiasis with osteoporosis, renal Fanconi's syndrome with chronic kidney disease, and idiopathic infantile hypercalcemia and nephrocalcinosis.
A patient was referred to our hospital due to hyponatremia, hyperkalemia, and hypophosphatemia, as well as persistent hypercalcemia after fluid therapy and sodium replacement. At admission to our hospital, potassium and sodium values were normal. After initiation of phosphorus therapy, hypokalemia and metabolic alkalosis were observed. Renal sonography showed bilateral medullary nephrocalcinosis. Analyses of the SLC34A1 gene were performed due to hypercalcemia and hypophosphatemia.
Gene analyses identified a novel homozygous c.682T>C (p.W228R) (p.Trp228Arg) mutation. There are no previous reports of patients with SLC34A1 gene mutations presenting with hypokalemia and metabolic alkalosis.
Herein, we present a case of infantile hypercalcemia 2 with a very different phenotype from that of previously described patients. Our findings provide further evidence for the wide range of phenotypic heterogeneity associated with NaPi-IIa impairment.
在生理条件下，近端肾小管通过 NaPi-IIa（和 NaPi-IIc）重吸收磷酸盐，以确保磷酸盐的体内平衡。SLC34A1 编码的 NaPi-IIa 的功能障碍与各种重叠的临床综合征有关，包括伴有骨质疏松症的低磷性肾结石、伴有慢性肾脏病的肾性范可尼综合征，以及特发性婴儿高钙血症和肾钙质沉着症。
由于低钠血症、高钾血症和低磷血症，以及液体治疗和钠替代后持续高钙血症，患者被转至我院。入院时，钾和钠值正常。开始磷治疗后，出现低钾血症和代谢性碱中毒。双侧肾髓质钙质沉着症的肾脏超声检查结果显示。由于高钙血症和低磷血症，对 SLC34A1 基因进行了分析。
基因分析发现了一种新的纯合 c.682T>C（p.W228R）（p.Trp228Arg）突变。以前没有报道过 SLC34A1 基因突变的患者出现低钾血症和代谢性碱中毒。
本文报告了一例婴儿高钙血症 2 型，其表型与以前描述的患者完全不同。我们的发现为 NaPi-IIa 功能障碍相关的广泛表型异质性提供了进一步的证据。
