Khandwala Hasnain M, Mumm Steven, Whyte Michael P
Division of Endocrinology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Endocr Pract. 2006 Nov-Dec;12(6):676-81. doi: 10.4158/EP.12.6.676.
To describe an elderly patient with low serum alkaline phosphatase (ALP) activity detected after a pathologic fracture and to characterize hypophosphatasia in adult patients.
We present a case report of a 64-year-old woman, who was referred after sustaining an atraumatic femoral fracture treated successfully with intramedullary nailing. Clinical, biochemical, radiologic, and molecular studies explore the differential diagnosis of her hypophosphatasemia, and the features, diagnosis, and management of the adult form of hypophosphatasia are reviewed.
Physical examination of our patient was revealing only for short stature. Bone mineral density evaluated by dual-energy x-ray absorptiometry was unremarkable. Biochemical investigations showed normal calcium, elevated inorganic phosphate, and low ALP levels in serum. In light of the hypophosphatasemia and pathologic fracture, the serum pyridoxal 5'-phosphate concentration was measured and found to be considerably elevated, a substantiation of the diagnosis of hypophosphatasia. Analysis of the gene encoding the "tissue-nonspecific" isoenzyme of ALP (TNSALP) demonstrated a novel, heterozygous, missense mutation causing her disorder.
Hypophosphatasia is a rare inborn error of metabolism due to a deactivating mutation (or mutations) of the gene encoding TNSALP, in turn leading to global deficiency of TNSALP activity and inadequate skeletal mineralization and fractures. Our patient illustrates the importance of low serum ALP activity in the assessment of patients with fractures. No established treatment exists for hypophosphatasia, but the correct diagnosis should help to avoid the use of traditional therapies for osteoporosis or osteomalacia, which would be ineffective or potentially harmful.
描述一名在病理性骨折后检测出血清碱性磷酸酶（ALP）活性降低的老年患者，并对成年患者的低磷酸酯酶症进行特征描述。
我们报告一例64岁女性病例，该患者因非创伤性股骨骨折接受髓内钉治疗成功后前来就诊。通过临床、生化、放射学和分子研究来探讨她低磷血症的鉴别诊断，并对成年型低磷酸酯酶症的特征、诊断和管理进行综述。
对我们这位患者的体格检查仅发现身材矮小。通过双能X线吸收法评估的骨密度无异常。生化检查显示血清钙正常、无机磷升高以及ALP水平降低。鉴于低磷血症和病理性骨折，检测了血清5'-磷酸吡哆醛浓度，发现其显著升高，这证实了低磷酸酯酶症的诊断。对编码ALP“组织非特异性”同工酶（TNSALP）的基因分析显示存在一种导致她患病的新型杂合错义突变。
低磷酸酯酶症是一种罕见的先天性代谢缺陷，由于编码TNSALP的基因发生失活突变，进而导致TNSALP活性全面缺乏以及骨骼矿化不足和骨折。我们的患者说明了血清ALP活性降低在骨折患者评估中的重要性。目前尚无针对低磷酸酯酶症的确立治疗方法，但正确诊断应有助于避免使用对骨质疏松症或骨软化症无效或可能有害的传统疗法。
