Comparison of total alkaline phosphatase and three assays for bone-specific alkaline phosphatase in childhood and adolescence

We compared serum levels of total alkaline phosphatase (TAP) and bone-specific alkaline phosphatase (BAP) as determined by three different assays (lectin affinity electrophoresis, immunoradiometric assay, enzyme-linked immunosorbent assay) in subjects aged 5–20 years suffering from X-linked hypophosphatemic rickets ( n = 14), chronic renal failure ( n = 10) and chronic cholestatic liver disease ( n = 16). Results were compared to controls of the same age and were expressed as standard deviation scores (SDS). TAP correlated significantly with BAP ( r > 0.9 for each assay; p <0.001) in controls. In children with cholestatic diseases, TAP (median SDS + 2.0) was elevated, but BAP, as measured by the electrophoretic assay, was within the reference range for most patients (median SDS: -0.4; p = 0.003 for the difference between the median SDS of TAP and BAP). In contrast, results for BAP as determined by the two immunoassays were not significantly different from TAP in any of the three patient groups ( p > 0.05 in each group for both assays). In this study, the two immunoassays did not have a detectable advantage over lectin affinity electrophoresis in the determination of BAP.     

X-连锁低血磷性佝偻病的治疗现状及展望

X-连锁低血磷性佝偻病(XLH)属于遗传性代谢性骨病,发病机制复杂,在临床上较为罕见,其主要临床表现为骨骼畸形及身材矮小,致残率高,因而针对XLH进行及早诊断及治疗对患者康复具有极为重要的意义。传统治疗以补充磷酸盐和维生素D类似物为主,随着学者对XLH病理机制研究逐渐深入,分子靶向治疗等新型治疗方式横空出世,通过多学科联合诊断及治疗的方法为患者带去了福音。本文就XLH的临床特征、发病遗传机制、治疗现状及治疗的未来发展趋势进行综述。     

Severe Refeeding Hypophosphatemia in a CAPD Patient: A Case Report

Refeeding syndrome is defined as severe electrolyte and fluid shifts associated with metabolic abnormalities in malnourished, refeeding patients. Hypophosphatemia is its predominant concern, though its occurrence is unusual in uremic patients due to the concomitant hyperphosphatemia. This case study reports a 56-year-old woman on continuous ambulatory peritoneal dialysis (CAPD) therapy who was admitted for peritonitis. Ileus and diarrhea developed during admission; enteral feeding was given initially and then shifted to total parenteral nutrition (TPN) because of poor digestion. A lower concentration of phosphate was administered in the TPN formula initially due to high initial serum phosphate level. However, severe hypophosphatemia (0.3 mg/dL) developed on the second day after TPN supplementation. Continuous intravenous phosphate (total 6 mmol of phosphate) was supplied immediately. Unfortunately, the sudden onset of conscious loss and cardiac arrest happened on the third day of TPN. It should be emphasized that severe refeeding hypophosphatemia can also develop early in uremic patients with hyperphosphatemia.     

Persistent Hyperparathyroidism Is a Major Risk Factor for Fractures in the Five Years After Kidney Transplantation

The risk of fractures after kidney transplantation is high. Hyperparathyroidism frequently persists after successful kidney transplantation and contributes to bone loss, but its impact on fracture has not been demonstrated. This longitudinal study was designed to evaluate hyperparathyroidism and its associations with mineral disorders and fractures in the 5 posttransplant years. We retrospectively analyzed 143 consecutive patients who underwent kidney transplantation between August 2004 and April 2006. The biochemical parameters were determined at transplantation and at 3, 12 and 60 months posttransplantation, and fractures were recorded. The median intact parathyroid hormone (PTH) level was 334 ng/L (interquartile 151–642) at the time of transplantation and 123 ng/L (interquartile 75–224) at 3 months. Thirty fractures occurred in 22 patients. The receiver operating characteristic (ROC) curve analysis for PTH at 3 months (area under the ROC curve = 0.711, p = 0.002) showed that a good threshold for predicting fractures was 130 ng/L (sensitivity = 81%, specificity = 57%). In a multivariable analysis, independent risk factors for fracture were PTH >130 ng/L at 3 months (adjusted hazard ratio [AHR] = 7.5, 95% CI 2.18–25.50), and pretransplant osteopenia (AHR = 2.7, 95% CI 1.07–7.26). In summary, this study demonstrates for the first time that persistent hyperparathyroidism is an independent risk factor for fractures after kidney transplantation.     

危重病人的血磷变化及临床意义

目的 观察危重病人的血磷变化 ,探讨其临床意义。方法 对34例危重病人急性期血磷、血钙、血镁进行检测 ,并以21例正常人作为对照。结果 危重病组血磷较对照组明显降低(p<0.001) ,危重病组血磷与血钙、血镁之间均无相关性。结论 危重病时常伴有低磷血症 ,它在一定程度上提示了疾病危重性的存在 ,及时进行补磷治疗 ,有利危重病人的抢救。     

Overexpression of Dmp1 fails to rescue the bone and dentin defects in Fam20C knockout mice

FAM20C is a kinase phosphorylating the small-integrin-binding ligand, N-linked glycoproteins (SIBLINGs), a group of extracellular matrix proteins that are essential for bone and dentin formation. Previously, we showed that Sox2-Cre;Fam20C^fl/fl mice had bone and dentin defects, along with hypophosphatemia and significant downregulation of dentin matrix protein 1 (DMP1). While the assumed phosphorylation failure of the SIBLINGs is likely associated with the defects in the Fam20C-deficient mice, it remains unclear if the downregulation of Dmp1 contributes to these phenotypes. In this study, we crossed 3.6?kb Col1-Dmp1 transgenic mice with 3.6?kb Col1-Cre;Fam20C^fl/fl mice to overexpress Dmp1 in the mineralized tissues of Fam20C conditional knockout (cKO) mice. X-ray, micro-computed tomography, serum biochemistry and histology analyses showed that expressing the Dmp1 transgene failed to rescue the bone and dentin defects, as well as the serum levels of FGF23 and phosphate in the Fam20C-cKO mice. These results indicated that the downregulation of Dmp1 may not directly associate with, or significantly contribute to the bone and dentin defects in the Fam20C-cKO mice.