HYPOPHOSPHATAEMIC OSTEOMALACIA WITH COMPLETE RECOVERY

Tumour-induced Osteomalacia Secondary to a Sarcoma

Tumour-induced osteomalacia (TIO), is a rare paraneoplasatic syndrome found in >95% of benign tumours that secrete fibroblast growth factor 23 - a phosphaturic circulating hormone. A rare case of a TIO secondary to a sarcoma, in a 21-year old man with history of bone fractures and distinctive physical and biochemical characteristics is presented and discussed.

Anesthesia for oncogenic osteomalacia--a rare paraneoplastic syndrome

Two patients with a diagnosis of oncogenic osteomalacia are described. This rare disease, characterized by secretion of fibroblast growth factor-23 by the tumor cells, causes myopathy, extreme debilitation and severe osteopathy because of severe hypophosphatemia. Both patients presented with severe bone pain, pathological fractures and proximal muscle weakness. Multiple diagnostic tools had to be utilized to settle the diagnosis of this rare disease. Although supplemental therapy for hypophosphatemia is usually started preoperatively, surgical excision of the causative tumor is the only definite treatment. Surgery is almost always curative; however, there is a lack of discourse in the literature regarding the anesthetic implications for the disease. The complete pathophysiology of the disease, clinical picture, its diagnostic intricacies as well as the salient points in its anesthetic management are discussed in this report.

Tumor-induced osteomalacia: successful treatment by radio-guided tumor surgery

Tumor-induced osteomalacia is a rare syndrome characterized by urinary phosphate loss with hypophosphatemic osteomalacia. The proposed pathogenetic mechanism is paraneoplastic secretion of phosphaturic factors (so-called phosphatonins).We describe a 34-year-old male patient who presented with severe pain of the spine and ribs for at least 2 years. Bone scintigraphy using Technetium hydroxymethylene diphosphonate (Tc HDP) showed multiple lesions suggesting metastatic disease. Bone biopsy however revealed osteomalacia. The patient had subnormal plasma phosphate levels (0.42 mmol/L; normal range, 0.87-1.45) and markedly increased phosphate clearance (82.8 mL/min; normal range, 5.4-16.2). The patient was treated with phosphate supplementation (up to 5 g daily) along with calcium (1000 mg daily) and calcitriol (1.5 microg daily). Although this therapy did not correct hypophosphatemia, it resulted in complete relief of pain within several months. (111)In pentetreotide scintigraphy showed a tiny lesion of 1-cm diameter, which could be localized to the left femoral neck in close vicinity to the greater trochanter by MRI and image fusion analysis. This lesion had not been visualized by Tc-99m HDP bone scintigraphy. Intraoperatively, use of a hand-held gamma probe after administration of (111)Indium pentetreotide ((111)In pentetreotide) clearly identified the tumor, which was completely removed and was shown to be a hemangiopericytoma. After removal of the tumor, phosphate metabolism normalized within 1 week without requirement of phosphate supplementation. Hypophosphatemic osteomalacia, although rare, raises an important differential diagnosis. An underlying tumor may be detected only by (111)In pentetreotide scintigraphy. Preoperative labeling with (111)In pentetreotide is a useful tool in detecting these tumors during surgery.This 34 year old man with osteomalacia had a small causative hemangiopericytoma detected in the indium pentetreotide scintography.

Pseudo-(tumor-induced) rickets

An athletic 8-year-old boy developed severe muscle weakness over 2 years. At the age of 10 years, investigation for possible neuromuscular disease disclosed hypophosphatemia (1.8 mg/dl) and rickets. There was selective renal tubular wasting of inorganic phosphate (Pi) but no history of toxin exposure, familial bone or kidney disease, or biochemical evidence of vitamin D deficiency. Urine amino acid quantitation was unremarkable. Serum 1,25-dihydroxyvitamin D [1,25(OH)2D] concentration was in the lower half of the reference range. Our presumptive diagnosis was tumor-induced rickets; however, physical examination and bone scanning in search of a neoplasm were unrevealing. Soon after 1,25(OH)2D3 and Pi treatment began, muscle strength improved considerably. After 6 months of therapy, radiographic abnormalities were substantially better. During the next 6 years, physical examinations, a second bone scan, whole-body and nasal sinus magnetic resonance imaging, and octreotide scintigraphy were unremarkable. When his physes fused at the age of 16 years, assessment of his course showed excellent control of his rickets requiring decreasing doses of medication. Furthermore, fasting serum Pi levels and tubular maximum phosphorus/glomerular filtration (TmP/ GFR) values had increased steadily and normalized after 3 years of treatment. Accordingly, therapy was stopped. Seven months after stopping medication, he continues to feel completely well. Fasting serum Pi levels, TmP/GFR, other biochemical parameters of bone and mineral homeostasis, creatinine clearance, and renal sonography are normal. Neither spontaneous or pharmacologic cure of tumor-induced rickets or osteomalacia nor a patient matching ours has been reported. His disorder, which we call pseudo-(tumor-induced) rickets, should be considered when investigation for oncogenic rickets or osteomalacia discloses no causal lesion. Consequently, prolonged medical therapy and futile searches for a neoplasm may be avoided.

Tumor-induced osteomalacia

Tumor-induced (oncogenic) osteomalacia is a rare clinicopathologic entity in which the clinical signs and symptoms of osteomalacia and the specific laboratory abnormalities of hypophosphatemia, hyperphosphaturia, and low serum levels of 1,25(OH)2 vitamin D are associated with the finding of a neoplastic process in the patient. To date, less than 100 cases of oncogenic osteomalacia have been described. We report a new case of adult-onset hypophosphatemic osteomalacia leading to the discovery of an asymptomatic phosphaturic mesenchymal lung tumor. Complete resection of the pulmonary neoplasia was followed by rapid normalization of the laboratory findings and clinical remission. The clinical, laboratory, and histopathologic spectrum of tumor-induced osteomalacia is presented, and the postulated mechanism of this condition is discussed in light of the relevant literature. The presence of occult neoplasms should be considered in cases of unexplained adult osteomalacia, with the physician's efforts being rewarded by the dramatic cure that follows excision of the tumor.

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.

Vitamin D-resistant rickets associated with epidermal nevus syndrome: demonstration of a phosphaturic substance in the dermal lesions

A 5-year-old boy was found to have severe rickets in association with hyperpigmented, linear, verrucous, epidermal tumors, typical of the epidermal nevus syndrome. Normocalcemia (9.6 mg/dl), hypophosphatemia (2.0 mg/dl), elevated serum alkaline phosphatase concentration (313 IU), decreased renal tubular reabsorption of phosphorus (35%), radiologic evidence of rickets, and lack of response to usual therapeutic doses of vitamin D suggested hypophosphatemic vitamin D-resistant rickets. Therapy with vitamin D in doses to 750,000 IU and oral phosphate, 2.0 gm/day, failed to induce healing of the rickets. A subtotal parathyroidectomy performed when the patient was 9 years old was also without effect. When he was 12 years old several fibroangiomas on the face and left lower limb were excised. Within three months all biochemical abnormalities resolved and radiologic evidence of healing was observed. A portion of excised tissue was homogenized and injection of the supernate into a 6-week-old puppy induced excessive phosphaturia. The data suggest that the rickets was induced by a phosphaturic substance extractable from the tumors.

Hypophosphataemic osteomalacia associated with a malignant tumour of the tibia: report of a case

A case of vitamin D resistant hypophosphataemic osteomalacia with glycosuria and aminoaciduria is reported. The course of the disease was dramatically altered by the removal of a bone sarcoma which probably had been growing slowly since the onset of the patient's symptoms five years previously. The histology and electron microscopy of the tumour are described. Three years after the operation the patient remains free of symptoms.

Myopathy in hypophosphataemic osteomalacia presenting in adult life

Three cases of hypophosphataemic osteomalacia presenting in adult life, in which a myopathy was a prominent presenting feature, are described. In one, a nasopharyngeal haemangioma was also present. Possible mechanisms underlying the myopathy are discussed briefly.

Osteomalacia associated with renal bicarbonate loss

Severe osteomalacia of uncertain etiology was observed in a 44-year-old woman. There was no evidence of chronic renal insufficiency, malabsorption, or of the renal tubular defects classically associated with osteomalacia. However, the dietary history suggested vitamin D deficiency and most of the biochemical findings were compatible with this condition. The unusual feature of the case was a decrease in plasma bicarbonate levels which appeared to be due to a lowered renal tubular threshold for bicarbonate reabsorption. There was no renal tubular defect with respect to hydrogen ion excretion.Rapid symptomatic and radiologic improvement occurred when the dietary intake of vitamin D was increased to approximately 200 I.U. per day and the acidosis was simultaneously corrected with sodium bicarbonate. Although no firm conclusions could be drawn about the relative importance of vitamin D deficiency or chronic acidosis in the production of the osteomalacia, the possibility that the chronic acidosis may have been a major contributing factor is discussed.