Cases reported "Osteomalacia"

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1/15. Lambda light chain induced nephropathy: a rare cause of the fanconi syndrome and severe osteomalacia.

    The fanconi syndrome is a generalized disorder of proximal renal tubular transport characterized by wasting of phosphate, amino acids, glucose, bicarbonate, and uric acid. The association of the acquired fanconi syndrome with lambda light-chain proteinuria is rare. We report the third case in the English language literature. A 65-year-old man presented with severe pelvic pain. Investigations showed an elevated serum creatinine level, and a 24-hour urine collection contained 2.56 g protein. The fanconi syndrome was diagnosed, with findings of phosphaturia, glycosuria, and aminoaciduria. bence jones protein (lambda sub-type) was present in the urine at a concentration of 0.58 g/L. Monocytic cells in the bone marrow and proximal tubular cells in the kidney contained cytoplasmic crystalline inclusions. Undecalcified bone sections confirmed the clinical diagnosis of osteomalacia. The patient was treated with phosphate, calcium, and ergocalciferol and experienced significant symptomatic improvement. The fanconi syndrome caused by light-chain deposition in proximal tubular cells is well described in the literature. However, it is rare for the light chains to be of the lambda subtype. This may reflect differences in the physicochemical properties of kappa and lambda light chains.
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2/15. Use of long-term intravenous phosphate infusion in the palliative treatment of tumor-induced osteomalacia.

    Tumor-induced osteomalacia is characterized by paraneoplastic defects in vitamin D metabolism, proximal renal tubular functions, and phosphate transport. The resulting hypophosphatemia can cause generalized pain and muscle weakness, which significantly affect the quality of life of the patients. Palliative treatment with calcium, vitamin d, and phosphate replacement is indicated for patients in whom the causative tumor cannot be completely resected. In this report we describe a case of tumor-induced osteomalacia in whom adequate oral doses of phosphate could not be used because of gastrointestinal side-effects. Long term (3-6 months) iv phosphate infusion delivered by ambulatory infusion pumps in combination with oral calcium and vitamin d was used successfully to decrease pain and increase muscle strength. Careful monitoring of serum calcium, phosphate, and creatinine levels and reliable microinfusion technology have allowed the long term use of iv phosphate infusion without serious morbidity. This patient received repeated (three times) phosphate infusions over 8 yr, resulting in laboratory and symptomatic improvement after each course. However, this patient did suffer two episodes of central venous catheter-related infection. Because of potentially serious complications, such as severe hypocalcemia, calcified right ventricular thrombi, and nephrocalcinosis, long term iv phosphate infusion should be reserved for patients who cannot tolerate adequate doses of oral phosphate and for whom the benefits outweigh the risks.
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3/15. A case of neuroendocrine oncogenic osteomalacia associated with a PHEX and fibroblast growth factor-23 expressing sinusidal malignant schwannoma.

    Oncogenic osteomalacia is a rare paraneoplastic syndrome that is characterized biochemically by hypophosphatemia and low plasma 1,25-dihydroxyvitamin D3, and clinically by osteomalacia, pseudofractures, bone pain, fatigue, and muscle weakness. We present a patient with a malignant schwannoma as the underlying cause of this disorder. A permanent cell line (HMS-97) derived from this tumor showed evidence of neuroendocrine differentiation by immunohistochemistry and of neurosecretory activity by electron microscopy. The cell line did express PHEX (phosphate-regulating gene with homologies to endopeptidases located on the X-chromosome) and FGF-23 (fibroblast growth factor-23) transcripts on northern hybridization; however, none of the known mutations from the related mendelian disorders of X-linked hypophosphatemic rickets or autosomal-dominant hypophosphatemic rickets could be detected. Tumor cell (HMS-97)-derived conditioned medium did not inhibit phosphate transport in a standard opossum kidney cell assay and in animal experiments. The medium also showed no PTH1- or PTH2-receptor-stimulating bioactivity. HMS-97 cells might be useful for further studies that aim to determine the genetic mechanism that leads to the observed PHEX and FGF-23 expression, both of which might have a direct role in the pathogenesis of oncogenic osteomalacia. In addition, these cells might be a useful tool for the investigation of neuroendocrine Schwann cell function and autoimmune peripheral nerve disease.
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4/15. Early skeletal effect of alkali therapy upon the osteomalacia of renal tubular acidosis.

    The administration of alkaline agents to a 16-year-old girl with severe renal tubular acidosis and osteomalacia caused an almost immediate rise of the urinary excretion of total hydroxyproline. The increment of the dyalizable fraction predominated over the nondyalizable component. Gradually serum phosphate and serum alkaline phosphatase increased whereas urinary calcium and magnesium and phosphate clearance declined. serum PTH remained elevated throughout. We suggest that the correction of the metabolic acidosis might increase the transport of phosphate and calcium across the functional bone membrane leading to a rapid deposition of lime salts in the uncalcified matrix with a concomitant increase in bone collagen turnover.
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5/15. fibroblast growth factor 7: an inhibitor of phosphate transport derived from oncogenic osteomalacia-causing tumors.

    Oncogenic osteomalacia (OO), a tumor-associated phosphate-wasting syndrome, provides an opportunity to identify regulators of renal phosphate homeostasis. We established cultures from OO-associated tumors. Conditioned medium from these cultures inhibited phosphate uptake in renal tubular epithelial cells. We then compared rna from tumor-derived cultures expressing inhibitory activity with rna from tumor-derived cultures in which inhibitory activity was not evident and identified candidate mRNAs specifically expressed by cultures inhibiting renal phosphate transport. Testing of identified candidates revealed that one protein, fibroblast growth factor 7 (FGF7), was a potent and direct inhibitor of phosphate uptake in vitro. A neutralizing monoclonal antibody to FGF7 reversed FGF7-dependent phosphate transport inhibition and inhibitory activity in conditioned medium from tumor cell cultures. immunoassay revealed abundant FGF7 in inhibitory conditioned medium and minimal amounts in nonconditioned medium or conditioned medium with no phosphate transport inhibitory activity. Furthermore, only small amounts of FGF23 were present in inhibitory conditioned medium, comparable to concentrations found in conditioned medium with no phosphate transport inhibitory activity. Thus, FGF7 was specifically identified when selecting for in vitro phosphate transport inhibitory activity of tumor-derived cultures and was confirmed as a potent inhibitor of phosphate transport. Finally, FGF7 message was confirmed in PCR products of mRNA extracted from fragments of each tumor. Members of the FGF family (other than FGF23) are expressed by OO-associated tumors and may play a role in mediating this syndrome.
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6/15. Oncogenous osteomalacia: a case study.

    A case of oncogenous osteomalacia due to a fibrosarcoma of the maxilla is reported, with a 19 year course before treatment. Metabolic studies of calcium and phosphorus were performed 3 and 19 years after the first symptomology. There was a negative balance for both phosphorus and calcium with low serum levels of 1,25-dihydroxyvitamin D which were corrected by resection of the tumor. Portions of the tumor were cultured and the supernatant did not affect phosphorus transport by a proximal tubule kidney cell line. Other portions were injected into athymic nude mice where they resulted in hypophosphatemia and phosphaturia, thus confirming the endocrine nature of the oncogenous osteomalacia factor.
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7/15. Metabolic studies in a patient with idiopathic hypophosphatemic osteomalacia.

    Studies were conducted in a patient with idiopathic hypophosphatemic osteomalacia to delineate the roles of parathyroid hormone (PTH), vitamin d and renal tubular function. A 43-year-old woman presented with progressive skeletal pains resulting in severe incapacity. Workup revealed: hypophosphatemia with a low tubular maximal phosphate reabsorption per glomerular filtrate (TmP/GFR) of 1.05 mg/dl, normocalcemia, hypocalciuria, elevated alkaline phosphatase and glycinuria. PTH and urinary cyclic amp (UcAMP) were normal, while calcitriol was low. Renal tubular acidosis or other transport defects were not present and no tumor was found. biopsy was diagnostic for osteomalacia, and the patient responded to 1-alpha OHD3 and phosphate therapy. hyperparathyroidism was ruled out by 1) normocalcemia persisting after 1-alpha OHD3 and calcium loading and 2) normal PTH and UcAMP challenged by phosphate supplements. Combined calcium and 1-alpha OHD3 administration resulted in hypercalciuria, decreased UcAMP and increased, but not corrected, TmP/GFR. These findings suggest that the osteomalacia was due to hypophosphatemia caused by a renal leak. PTH is only contributory to the phosphaturia. Low calcitriol level contributes to the osteomalacia directly and indirectly through impaired mineral absorption and, therefore, is also responsible for the hypocalciuria.
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8/15. adult hypophosphatemic osteomalacia: report of two cases.

    Two cases of late hypophosphatemic osteomalacia are described: a male aged 30 who had the disease since he was 22 and a woman of 23 who had the disease since she was 14. Both presented with myopathy and bone pain, and showed hypophosphatemia, hyperglycinuria, reduced tubular phosphate reabsorption (TPR), increased hydroxyprolinuria and normal iPTH and iCT values. Radiologically the male had no Looser's zones and the woman did. Bone biopsy confirmed hypophosphatemic osteomalacia. Both cases were treated with vitamin d and oral phosphate and no improvement was observed. When treatment with 25(OH)D3 was initiated, no improvement was seen and afterwards this was combined with treatment using 1.25(OH)2D3 and from this time on a clinical improvement of the myopathy became evident in both patients. In the woman, healing of the bone lesions occurred at the same time as that of the myopathy, whereas in the male the bone lesions became worse. Healing of the myopathy was only obtained when treatment with 1.25(OH)2D3 was begun. Both patients had reduced values of 2.3 erythrocytic DPG and low level of serum phosphorus when the myopathy was cured, which suggests a lack of effect of 2.3 DPG or serum phosphorus as a cause of the myopathy. Although this had been attributed to a deficiency in the function of 25(OH)D3, the response to 1.25(OH)2D3 and due to the effects of this metabolite on calcium transport in muscle, suggests that the myopathy which occurs in late hypophosphatemic osteomalacia is a result of deficiency or resistance to the muscular effect of this metabolite. We cannot explain the lack of bone healing in the man and further therapeutic studies are required.
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9/15. fanconi syndrome associated with a non-ossifying fibroma of bone.

    A 20-year-old man presenting with osteomalacia was found to have the fanconi syndrome, as evidenced by hypophosphatemia with hyperphosphaturia, glycosuria in the presence of normoglycemia, and generalized aminoaciduria. After removal of a non-ossifying fibroma of the left tibia, the renal tubular abnormalities promptly resolved with subsequent healing of the osteomalacia. A humoral factor released from the tumor may have caused the disorder in proximal renal tubular cell transport.
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10/15. The concurrence of hypoparathyroidism provides new insights to the pathophysiology of X-linked hypophosphatemic rickets.

    Controversy exists over the role that PTH and extracellular fluid calcium concentration may play in modulation of the renal phosphate transport defect in X-linked hypophosphatemic rickets. In previous studies, administration of PTH to affected subjects resulted in an increase or no effect on renal phosphate excretion, while calcium infusion increased renal tubular phosphate transport. In contrast, patients with X-linked hypophosphatemic rickets and hyperparathyroidism have no change in their renal phosphate wasting after parathyroidectomy. However, none of these were permanently hypoparathyroid postoperatively. We describe a patient with idiopathic hypoparathyroidism in whom we proved the coexistence of X-linked hypophosphatemic rickets using family history and dental abnormalities. Initially, the patient had a mean serum calcium level of 5.6 /- 0.07 ( /- SE) mg/dl and a renal tubular maximum for reabsorption of phosphate per liter glomerular filtrate (TmP/GFR) of 6.5 /- 0.46 mg/dl. hypoparathyroidism was confirmed, and therapy with vitamin d (50,000 U/day) and calcium (1,000 mg/day) was begun. On this regimen, serum calcium rose to 8.1 /- 0.2 mg/dl, and TmP/GFR declined to 2.59 /- 0.12 mg/dl. Bone biopsy revealed the persistence of osteomalacia. Subsequently, therapy with 1,25-dihydroxyvitamin D3 (1.0 microgram/day) was initiated, and serum calcium rose to 9.6 /- 0.07 mg/dl, and TmP/GFR declined to 1.79 /- 0.16 mg/dl. The prevailing serum calcium level correlated inversely with the TmP/GFR (r2 = 0.91; P less than 0.001). These data indicate that calcium and/or PTH are involved in modulation of the renal phosphate transport defect in X-linked hypophosphatemic rickets.
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