Renal Phosphate Wasting in Fibrous Dysplasia of Bone Is Part of a Generalized Renal Tubular Dysfunction Similar to That Seen in Tumor-Induced Osteomalacia
作者:Michael T. Collins、Caroline Chebli、Janet Jones、Harvey Kushner、Mark Consugar、Piero Rinaldo、Shlomo Wientroub、Paolo Bianco、Pamela Gehron Robey
DOI:10.1359/jbmr.2001.16.5.806
日期:——
Fibrous dysplasia (FD) of bone is characterized by focal replacement of normal bone and marrow with abnormal bone and fibrous tissue. It arises from postzygotic activating mutations of the GNAS1 gene. Hypophosphatemia due to renal phosphate wasting has been reported in association with FD as a part of the McCune‐Albright Syndrome (MAS), which is characterized by FD, skin hyperpigmentation, and precocious puberty. To date, the prevalence and mechanism of phosphate wasting has not been well studied. We evaluated 42 patients with FD/MAS. Serum and urine samples were tested for indices of mineral metabolism, amino acid handling, and markers of bone metabolism. Twenty (48%) patients had some degree of renal phosphate wasting. Nephrogenous cyclic adenosine monophosphate (cAMP) was normal in FD patients, suggesting that the underlying cause of phosphate wasting is not the presence of activating GNAS1 mutations in the kidney. In addition, there was evidence of a more generalized renal tubulopathy as represented by the presence of abnormal vitamin D metabolism, proteinuria in 36 (86%) patients, and aminoaciduria in 39 (94%) patients. Renal phosphate wasting significantly correlated with the degree of bone involvement, as assessed by serum and urine markers of bone metabolism, suggesting that a circulating factor produced by FD bone and impacting on the kidney may be the mechanism. These data show that phosphaturia as part of a generalized renal tubulopathy represents the most common extraskeletal manifestation of FD and that the observed tubulopathy is similar to that seen in tumor‐induced osteomalacia (TIO).
骨骼纤维病(FD)的特点是正常骨骼和骨髓局部被异常骨骼和纤维组织替代。它源于GNAS1基因的合子后激活突变。由于肾脏磷排泄导致的低磷血症已被报告与FD相关,作为麦卡恩-阿尔布赖特综合征(MAS)的一部分,该综合征的特征是FD、皮肤色素沉着增多和性早熟。迄今为止,磷排泄的发生率和机制尚未得到充分研究。我们评估了42名FD/MAS患者,检测了血清和尿液样本中矿物代谢、氨基酸处理和骨代谢标志物的指标。20名(48%)患者有不同程度的肾脏磷排泄。FD患者的肾源性环腺苷酸(cAMP)正常,表明磷排泄的潜在原因不是肾脏中存在激活的GNAS1突变。此外,还发现有更广泛的肾小管病的证据,表现为异常的维生素D代谢,在36名(86%)患者中出现蛋白尿,在39名(94%)患者中出现氨基酸尿。肾脏磷排泄与骨骼受累程度显著相关,通过血清和尿液中的骨代谢标志物评估,表明FD骨骼产生的循环因子可能影响肾脏并成为机制。这些数据显示,作为全身性肾小管病的一部分,磷尿是FD最常见的额外骨外表现,并且观察到的小管病与肿瘤诱导性骨软化症(TIO)中所见的类似。