Eggert Christoph H, Albright Robert C
Department of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota 55905, USA.
Hemodial Int. 2006 Oct;10 Suppl 2:S51-5. doi: 10.1111/j.1542-4758.2006.00114.x.
A 19-year-old male presented with chest pain and dyspnea. He was anephric following nephrectomy for focal segmental glomerulosclerosis, had a subsequent failed transplant, and had been dialysis dependent for 3 years. Workup revealed hyperparathyroidism and an abnormal chest X-ray and computed tomography scan, significant for massive extra-skeletal pulmonary calcification. A markedly abnormal Technitium99 methylene diphosphonate (Tc99m-MDP) bone scan confirmed the clinical suspicion of metastatic pulmonary calcification. Metastatic pulmonary calcification (MPC) is common, occurring in 60% to 80% of dialysis patients on autopsy and bone scan series. It may lead to impaired oxygenation and restrictive lung disease. Typically, the calcium crystal is whitlockite rather than hydroxyapatite, which occurs in vascular calcification. Four major predisposing factors may contribute to MPC in dialysis patients. First, chronic acidosis leaches calcium from bone. Second, intermittent alkalosis favors deposition of calcium salts. Third, hyperparathyroidism tends to cause bone resorption and intracellular hypercalcemia. Finally, low glomerular filtration rate can cause hyperphosphatemia and an elevated calcium-phosphorus product. There may be other factors. Some authors suggest that the incidence of MPC in recent years may be lower due to improved dialysis techniques. The diagnosis is confirmed by biopsy, but can be suspected by typical findings on a Tc99m-MDP bone scan. Therapy is limited to ensuring adequate dialysis, correcting calcium-phosphorus product, and hyperparathyroidism; discontinuing vitamin D analogues may help. Conflicting reports show that transplantation may either improve or worsen the situation. MPC should be considered in dialysis patients who have characteristic abnormal chest radiography and/or pulmonary symptoms.
一名19岁男性出现胸痛和呼吸困难。他因局灶节段性肾小球硬化症接受肾切除术后无肾，随后移植失败，依赖透析3年。检查发现甲状旁腺功能亢进，胸部X线和计算机断层扫描异常，表现为大量骨骼外肺部钙化。锝99亚甲基二膦酸盐（Tc99m-MDP）骨扫描明显异常，证实了临床对转移性肺钙化的怀疑。转移性肺钙化（MPC）很常见，在尸检和骨扫描系列中，60%至80%的透析患者会出现。它可能导致氧合受损和限制性肺病。通常，钙晶体是白磷钙矿，而不是血管钙化中出现的羟基磷灰石。四个主要的易感因素可能导致透析患者发生MPC。首先，慢性酸中毒会从骨骼中浸出钙。其次，间歇性碱中毒有利于钙盐沉积。第三，甲状旁腺功能亢进往往会导致骨吸收和细胞内高钙血症。最后，低肾小球滤过率可导致高磷血症和钙磷乘积升高。可能还有其他因素。一些作者认为，由于透析技术的改进，近年来MPC的发病率可能较低。诊断通过活检确认，但典型的Tc99m-MDP骨扫描结果可提示怀疑。治疗仅限于确保充分透析、纠正钙磷乘积和甲状旁腺功能亢进；停用维生素D类似物可能会有帮助。相互矛盾的报告表明，移植可能改善或恶化病情。对于有特征性胸部X线异常和/或肺部症状的透析患者，应考虑MPC。
