Approaching virtual osteoid volume estimation and in-depth tissue characterization in patients with tumor-induced osteomalacia

Tumor-induced osteomalacia (TIO) poses a significant diagnostic challenge, leading to increased disease duration and patient burden also by missing clinical suspicion. Today, diagnosis of osteomalacia relies on invasive iliac crest biopsy, if needed. Therefore, a noninvasive method would be beneficial for patients with severe osteomalacia, such as TIO, to inform their clinical management and address specific needs, like estimating the regeneration capacity at high osteoid volumes (OVs) or the potential of a hungry bone syndrome after tumor removal. Furthermore, given the lack of comprehensive histological characterization of TIO, there is a need for additional tissue characterization. Therefore, our assessment encompassed iliac crest biopsies that were examined using quantitative electron backscattered microscopy, Raman spectroscopy, micro-computed tomography, and histology to analyze the biopsy tissue. Our clinical assessment encompassed DXA and high-resolution peripheral quantitative computed tomography (HR-pQCT) alongside with biochemical analyses and clinical evaluations. Combining imaging and clinical data, we established a model to predict the OV. We compared 9 TIO patients with 10 osteoporosis (OPO) patients and 10 healthy controls. Histological analyses confirmed a pronounced OV in TIO patients (OPO: 1.20% ± 1.23% vs TIO: 23.55% ± 12.23%, P < .0005), and spectroscopy revealed lower phosphate levels in TIO biopsies. By combining HR-pQCT and laboratory diagnostics, we developed a linear regression model to noninvasively predict the OV revealing significantly higher modeled OV/BVmodel values of 24.46% ± 14.22% for TIO compared to the control group (5.952% ± 3.44%, P ≤ .001). By combining laboratory diagnostics, namely, ALP and Tt.BMDRadius measured by HR-pQCT, we achieved the calculation of the virtual osteoid volume to bone volume ratio (OV/BVmodel) with a significant correlation to histology as well as reliable identification of TIO patients compared to OPO and control. This novel approach is potentially helpful for predicting OV by noninvasive techniques in diagnostic procedures and improving the clinical management of TIO.

Increased Uptake of Brown Tumor in 99m Tc-HYNIC-TOC Scintigraphy Mimicking Postoperative Recurrence of Tumor-Induced Osteomalacia

ABSTRACT

A 61-year-old man underwent a resection of tumor in the left tibia that caused osteomalacia 11 years ago. Postoperative bone pain and fatigue symptoms were briefly relieved but then recurred. To identify potential recurrent tumors, 99m Tc-HYNIC-TOC scintigraphy was performed. Images revealed an osteolytic lesion in the right tibia with increased uptake. The lesion was subsequently resected, which pathologically proved a brown tumor. Symptoms of bone pain and weakness caused by osteomalacia did not relieve 4 months after the operation. Here, we present a rare case of brown tumor with high activity on 99m Tc-HYNIC-TOC SPECT/CT, mimicking a culprit tumor of osteomalacia.

Bone Volumetric Density, Microarchitecture, and Estimated Bone Strength in Tumor-Induced Rickets/Osteomalacia Versus X-linked Hypophosphatemia in Chinese Adolescents

Tumor-induced rickets/osteomalacia (TIR/O) severely impairs bone microarchitecture and bone strength. However, no study has described the microarchitectural quality of bone in adolescent patients with TIR/O. TIR/O affects bone quality more severely than the inherited causes of hypophosphatemia, the most common form of which is X-linked hypophosphatemia (XLH). Nevertheless, differences of the microarchitectural quality of the bone between TIR/O and XLH have never been clarified. Therefore, in this study, we used high-resolution peripheral quantitative computed tomography to assess bone microarchitecture in five Chinese adolescent TIR/O patients, and these were compared with 15 age- and gender-matched XLH patients as well as 15 age- and gender-matched healthy controls. Compared with the healthy controls, the TIR/O patients presented with significantly lower volumetric bone mineral densities (vBMDs), severely affected bone microarchitecture, and profoundly weaker bone strength. The distal tibia was more severely affected than the distal radius. Compared with the XLH patients, the TIR/O patients showed deteriorated bone quality notably at the distal tibia and in the cancellous compartment, reflected by 45.9% lower trabecular vBMD (p = 0.029), 40.2% lower trabecular fraction (p = 0.020), 40.6% weaker stiffness (p = 0.058), and 42.7% weaker failure load (p = 0.039) at the distal tibia. The correlation analysis showed that a higher level of serum FGF23 and a lower level of serum phosphate were associated with a poorer bone microarchitecture and a weaker estimated bone strength in the hypophosphatemic patients of our study. In conclusion, our study demonstrated significantly lower vBMDs, severely impaired bone microarchitecture, and profoundly weaker bone strength in Chinese adolescent patients with TIR/O, notably at the distal tibia, compared with the same parameters in age- and sex-matched healthy controls and XLH patients, which was possibly caused by excessive FGF23 production and secretion, chronically severe hypophosphatemia, and weak mechanical stimulus at the lower extremities. These findings further our understanding of the impact of different kinds of hypophosphatemic rickets/osteomalacia on bone quality.

Utility of 18F-AlF-NOTA-Octreotide PET/CT in the Localization of Tumor-Induced Osteomalacia

CONTEXT

Tumor-induced osteomalacia (TIO) is a paraneoplastic disorder, usually caused by benign mesenchymal tumors that produce high levels of fibroblast growth factor 23. The only curative therapy is resection of the causative tumors.

OBJECTIVE

This research was conducted to evaluate the efficacy of 18F-AlF-NOTA-octreotide (18F-OC) positron emission tomography/computed tomography (PET/CT) in detecting TIO and its impact on patient management.

METHODS

Retrospective analysis was conducted of 17 patients with hypophosphatemic osteomalacia suspected to be TIO. A  18F-OC PET/CT study was performed in all 17 patients to localize the tumor and 68Ga-DOTATATE PET/CT was performed in 4 out of 17 patients; both studies were performed within 1 week of each other. Both studies were interpreted blindly without the knowledge of other imaging findings. The image findings were compared with the results of histopathological examinations and clinical follow-ups.

RESULTS

The 18F-OC PET/CT scans were positive in 14 patients. Furthermore, 4 of 14 patients were scanned with both 18F-OC and 68Ga-DOTATATE PET/CT. Both studies were able to localize the tumor in all 4 patients. In total, 14 patients had surgery to remove the lesions. Postsurgical pathological examination confirmed causative tumors in these patients, whose symptoms diminished promptly. Serum phosphate levels normalized, confirming the diagnosis of TIO. 18F-OC PET/CT sensitivity, specificity, and accuracy were 87.5%, 100%, and 88.2% respectively. 18F-OC PET/CT findings affected patient management in 88.2% of cases.

CONCLUSION

18F-OC PET/CT scan is useful in the detection of tumors causing TIO. Further studies with larger patient populations are needed to validate the result.

Radiotherapy for a rare phosphaturic mesenchymal tumor in the middle ear presenting with oncogenic osteomalacia: A case report

RATIONALE

Phosphaturic mesenchymal tumor (PMT) is a rare neoplasm causing oncogenic osteomalacia. Surgery remains the definitive treatment for PMT, and radiotherapy is seldom employed. However, surgery for PMT involving the head and neck is often difficult due to the local invasion and complicated anatomy. We report the first case of PMT, which was successfully treated with the combination of radiotherapy and supplementation of activated vitamin D.

PATIENT CONCERNS

A 55-year-old woman suffered from pain in the hip and bilateral femur. Serum phosphate and calcium decreased to abnormal levels. Serum alkaline phosphatase and fibroblast growth factor 23 increased to abnormal levels. The hearing loss of the right ear had continued and a middle ear tumor was revealed.

DIAGNOSES

Subsequent biopsy provided the diagnosis of PMT that caused oncogenic osteomalacia. These clinical and pathological characteristics were consistent with and provided the final diagnosis of benign PMT.

INTERVENTIONS

Surgery of the PMT was difficult and the patient underwent radiotherapy. The prescribed dose was 36 Gy in 10 fractions. Simultaneously, the patient started supplementation of 1,25-dihydroxyvitamin D3 (1-2 μg/day) and continued for 2 years.

OUTCOMES

Near-complete resolution of the symptoms was achieved and abnormal laboratory values recovered. At 5 years of follow-up, the irradiated tumor showed no regrowth. Severe hearing loss of the right ear was not observed.

LESSONS

Radiotherapy was effective for the PMT and could be an important treatment option for inoperable cases.

Diagnostic performance of 68Ga-DOTATOC PET/CT in tumor-induced osteomalacia

OBJECTIVE

Tumor-induced osteomalacia (TIO) is caused by typically small tumors that secrete fibroblast growth factor 23 (FGF23). As tumor resection is the only effective treatment for TIO, it is important to detect the culprit tumor. We aimed to assess the utility of ⁶⁸Gallium-DOTA-D-Phe(1)-Tyr(3)-octreotide (⁶⁸Ga-DOTATOC) PET/CT in TIO and the correlation between biochemical parameters and the PET/CT results.

METHODS

Thirty-five patients with clinically suspected TIO who had undergone ⁶⁸Ga-DOTATOC PET/CT were retrospectively analyzed. ⁶⁸Ga-DOTATOC PET/CT results were compared with biochemical parameters and the final diagnosis, including histopathology.

RESULTS

⁶⁸Ga-DOTATOC PET/CT detected focal uptake consistent with TIO in 21/35 patients, one of which was considered false positive. In 16 patients, the cause of osteomalacia was confirmed histologically as phosphaturic mesenchymal tumor (n = 15) or fibrous dysplasia (n = 1). The other four patients were judged clinically as true positive by subsequent MRI and the clinical course. Overall, the detection rate of ⁶⁸Ga-DOTATOC PET/CT was 57% (20/35). Median tumor maximum standardized uptake value (SUVmax) was 6.9 (range 1.5-37.7). There was no significant difference in serum intact FGF23 level between DOTATOC-positive and DOTATOC-negative cases, and no significant correlation was observed between intact FGF23 level and tumor SUVmax.

CONCLUSIONS

⁶⁸Ga-DOTATOC PET/CT was clinically useful in detecting culprit tumors and subsequent patient management in TIO.

An Investigation of Micro-CT Analysis of Bone as a New Diagnostic Method for Paleopathological Cases of Osteomalacia

OBJECTIVE

This paper looks to broaden the methodological possibilities for diagnosing osteomalacia in archaeological bone using micro-CT analysis. Increasing the identification of osteomalacia in paleopathology will provide support for important interpretive frameworks.

MATERIALS

Nine embedded and two unembedded rib fragments were sourced from St. Martin's Birmingham and Ancaster, UK, and Lisieux Michelet, France. Of the 11 samples, nine were previously confirmed as osteomalacic, and presented with varying levels of diagenesis and two were non-osteomalacic controls, one of which exhibits diagenetic change.

METHODS

Micro-CT, backscattered scanning electron microscopy, and light microscopy were employed. Micro-CT images were evaluated for osteomalacic features using corresponding microscopic images.

RESULTS

Micro-CT images from osteomalacic samples demonstrated the presence of defective mineralization adjacent to cement lines, areas of incomplete mineralization, and resorptive bays/borders, three key diagnostic features of osteomalacia. Diagenetic change was also detectable in micro-CT images, but did not prevent the diagnosis of osteomalacia.

CONCLUSIONS

Micro-CT analysis is a non-destructive method capable of providing microstructural images of osteomalacic features in embedded and unembedded samples. When enough of these features are present, micro-CT images are capable of confirming a diagnosis of osteomalacia.

SIGNIFICANCE

Vitamin D deficiency has important health consequences which operate throughout the life course. Increasing the ability to detect cases of vitamin D deficiency provides researchers with a greater understanding of health and disease in past communities.

LIMITATIONS

Only adult rib samples were used.

SUGGESTIONS FOR FURTHER RESEARCH

Paleopathologists should look to test the utility of micro-CT analysis in diagnosing active rickets in subadult individuals.

Elevated FGF23 in a patient with hypophosphatemic osteomalacia associated with neurofibromatosis type 1

CONTEXT

The mechanism behind hypophosphatemia in the setting of neurofibromatosis type 1 (NF1) is not known. We describe a possible role of fibroblast growth factor-23 (FGF23) in the pathophysiology of hypophosphatemia in a patient with NF1.

CASE DESCRIPTION

A 34-year woman with NF1 presented with severe hypophosphatemia, osteomalacia, and elevated plasma FGF23. The patient had considerable improvement on replacement of oral phosphate. Two Ga68 DOTANOC PET-CT scans over a period of 2 years failed to detect any localized uptake. Immuno-staining for FGF23 was absent in the neural-derived tumour cells of the neurofibromas in the proband.

CONCLUSION

The patient with NF1 had elevated circulating FGF23. Tumour cells in the neurofibroma tissues did not stain for FGF23 on IHC. It is unlikely for neurofibromas to contribute to high circulating FGF23 levels in the proband.

Severe hypophosphatemia induced by denosumab in a patient with osteomalacia and tenofovir disoproxil fumarate-related acquired Fanconi syndrome

Denosumab, a novel agent that inhibits osteoclasts, reduces the risk of fracture in patients with osteoporosis. However, worsening of hypophosphatemia and other symptoms may be induced by denosumab in patients with pre-existing hypophosphatemic osteomalacia. A 58-year-old man with hepatitis B presented with diffuse bone pain and muscle weakness. Denosumab was prescribed by the orthopedist according to documented low bone mass and spine compression fracture. After administering denosumab, the patient's bone pain worsened, and he later developed a right tibia stress fracture. His condition was diagnosed as adult-onset hypophosphatemic osteomalacia complicated by multiple bone fractures, which resulted from Fanconi syndrome with proximal tubulopathy due to tenofovir disoproxil fumarate (TDF) treatment for his hepatitis B. Denosumab use leads to aggressive hypophosphatemic osteomalacia and the complication of stress fractures, because of its effects on bone resorption. Physicians should be aware that in patients with chronic hepatitis B monoinfection who are administered TDF therapy, bone pain or fracture is possible but preventable by timely monitoring of serum phosphate levels. Denosumab should not be used in patients with untreated osteomalacia or vitamin D deficiency, as it may lead not only to hypocalcemia but also to hypophosphatemia in these patients.

Radiographically recognizable? An investigation into the appearance of osteomalacic pseudofractures

Pseudofractures, lucent bands that occur due to a build-up of osteoid, are a key feature of osteomalacia. In paleopathology, pseudofractures are often marked by small, linear cracks in the cortex of the bone surrounded by irregular, bony spicule formation. Radiography can be used to help diagnose pseudofractures, both clinically and in paleopathology. A detailed understanding of the radiographic appearance of pseudofractures and their development is, therefore, necessary to aid a diagnosis of vitamin D deficiency. The present study examined the clinical literature to determine current ideas on the appearance of pseudofractures with the aim of applying this knowledge to paleopathology. A radiographic study of the characteristics of pseudofractures was performed on five individuals with clear skeletal features of osteomalacia from archaeological sites in Canada and the United Kingdom dating to the medieval period (5th to 15th centuries) and the 18th to 19th century. Results show that the radiographic appearance of pseudofractures could potentially reveal information about the cause of the deficiency and the chronicity of pseudofractures. This type of information has the potential to further our understanding of the lived experiences of archaeological individuals with osteomalacia.

Four possible cases of osteomalacia: The value of a multidisciplinary diagnostic approach

Rickets and residual rickets are often encountered in Dutch archeological skeletal samples. However, no archeological Dutch paleopathological case of adult osteomalacia has been described in literature to date. This paper describes the first four archeological Dutch paleopathological cases of osteomalacia and assesses the value of the various modalities (macroscopic assessment, radiology and histology) that may be used for diagnosis. The skeletal remains investigated originate from the Meerenberg psychiatric hospital cemetery in Bloemendaal, the Netherlands, and date from 1891 - 1936. The remains of 69 adult individuals were inspected for macroscopic lesions which may be associated with osteomalacia. In cases suspect for osteomalacia, complimentary radiological and histological investigations (BSE-SEM and light microscopy) were performed. Macroscopically, four individuals presented with lesions (highly) suggestive of osteomalacia. Histological examination (both BSE-SEM and light microscopy) provided valuable information to come to an eventual diagnosis of osteomalacia in all four cases. Light microscopy proved to be an feasible alternative for BSE-SEM. The added value of radiological analyses was limited. The individuals identified were most likely patients in the psychiatric hospital, and the reason for their institutionalization and/or the regime in the institution may have played a role in the development of the osteomalacia observed.

[Bone biopsy in the Chronic Kidney Disease (CKD)]

Histomorphometry or quantitative histology is the analysis on histologic sections of bone resorption, formation and structure parameters. It is the only technique allowing a dynamic evaluation of osteoblast activity after labelling with tetracycline. In addition, the use of computed image analyzer allows the possibility to assess bone microarchitecture. Histomorphometric bone biopsy is a reliable and well-tolerated procedure. Bone samples are taken at iliac crest level under local anesthesia and sedation. Samples are put into methyl-metacrilate resin where the sections are prepared for the microscopic analysis of different histomorphometric parameters. Histomorphometry is used to exclude or confirm the diagnosis of osteomalacia and also to evaluate bone damage associated with particular treatments (for example, glucocorticoids, anticonvulsants) or in case of rare bone diseases (osteogenesis imperfecta). Recently, this approach has been repurposed for the evaluation of bone disease during Chronic Kidney Disease, particularly to differentiate high and low bone turnover osteodystrophy. Kidney Disease Improving Global Outcomes (KDIGO) guidelines have pointed out the situations requiring bone biopsy for histomorphometric analysis. New techniques using molecular biology will improve the accuracy and predictive value of this approach.

The diagnostic dilemma of tumor induced osteomalacia: a retrospective analysis of 144 cases

Diagnostic delay of tumor induced osteomalacia (TIO) is common in clinic practice. To investigate the diagnostic condition of TIO in China and raise clinicians' awareness of TIO, we retrospectively analyzed clinical manifestations, biochemical features, and specially evaluated missed diagnoses and misdiagnoses among 144 TIO patients from Peking Union Medical College Hospital during December 1982 to December 2014. Clinical presentations of TIO mainly included bone pain, difficulty in walking, pathological fractures, muscle weakness, and height loss. TIO patients demonstrated hypophosphatemia (0.48±0.13 mmol/L), elevated serum alkaline phosphatase (277.9±152.6 U/L), reduced tubular maximum for phosphorus/glomerular filtration rate (0.39±0.14) and markedly elevated serum fibroblast growth factor 23 (FGF23) (median level 302.9 pg/mL). The average time from onset to a correct diagnosis was 2.9±2.3 years while the mean duration from onset to tumor resection was 5.4±4.2 years. The initial misdiagnosis rate was 95.1% (137/144) and 240 case-times of misdiagnoses occurred among the 144 cases. The most frequent misdiagnoses were intervertebral disc herniation, spondyloarthritis (including ankylosing spondylitis) and osteoporosis. A total of 43.1% (62/144) cases with hypophosphatemia presented on their laboratory sheets were neglected and missed diagnosed. Our study showed that TIO was frequently misdiagnosed and missed diagnosed due to its rarity, insidious onset, nonspecific clinical manifestations and clinicians' poor recognition. It is necessary to test serum phosphorus in patients with musculoskeletal symptoms and difficulty in walking. The measurement of serum FGF23 is rather valuable. Once hypophosphatemia is discovered, TIO should be suspected and it is highly recommended to search for tumors and perform curative surgery.

Adult-onset hypophosphatemic osteomalacia associated with Sjogren syndrome: Clinical case report

RATIONALE

Hypophosphatemic osteomalacia (HO) is a metabolic bone disease, exhibiting different etiologies such as genetic mutation, tumor induction, dysimmunity, or renal disease. Sjogren's syndrome (SS) is a connective tissue disorder commonly involving exocrine glands; however kidney involvement is also encountered, leading to abnormal phosphorus metabolism, even HO.

PATIENT CONCERNS

A 47-year-old female patient presented progressively worsening pain in the chest wall, back and bilateral lower extremities as well as muscle weakness was referred to our department.

DIAGNOSES, INTERVENTIONS AND OUTCOMES

Due to the laboratory test results, radiographic findings and pathologic results, she was diagnosed with adult-onset HO associated with SS. She was then treated with alkalinization, steroids, neutral phosphate, calcium supplements together with activated vitamin D. So far, she recovered uneventfully with relieved pain and increased serum phosphorus level.

LESSONS

HO may be secondary to renal tubular acidosis of SS patients, and it might be a diagnostic challenge when the kidney involvement in SS is latent and precede the typical sicca symptoms.

Osteomalacia induced by long-term low-dose adefovir dipivoxil: Clinical characteristics and genetic predictors

CONTEXT

Adefovir dipivoxil (ADV) was an important cause of adult-onset hypophosphatemic osteomalacia. However, its clinical characteristics and mechanisms have not been well defined.

OBJECTIVE

The objective of the study was to summarize the clinical characteristics of ADV-induced osteomalacia and to explore the association between ADV-associated tubulopathy and polymorphisms in genes encoding drug transporters.

DESIGN, SETTING, PATIENTS, AND MAIN OUTCOME MEASURE

Seventy-six affected patients were clinically studied. The SLC22A6 and ABCC2 genes were screened and compared with healthy people from the HapMap.

RESULTS

Hypophosphatemia, high serum alkaline phosphatase (ALP) levels, hypouricemia, nondiabetic glycosuria, proteinuria, metabolic acidosis and high bone turnover markers were the main metabolic characteristics. Fractures and pseudofractures occurred in 39 patients. Stopping ADV administration, supplementing calcitriol and calcium was effective during the follow-up period. Single SNP analysis revealed a higher percentage of the G/A genotype at c.2934 in exon 22 of the ABCC2 gene (rs3740070) in patients than in healthy people (12% [7 of 58 patients] vs. 0% [0 of 45 patients]; P=0.017), while there was no subject with homozygosity for the A allele at c.2934.

CONCLUSIONS

ADV can be nephrotoxic at a conventional dosage. The G/A genotype at c.2934 of the ABCC2 gene may be a predictor of patients at greater risk for developing ADV-associated tubulopathy. Larger case-control studies are needed to further verify this finding.

Radiology of Osteogenesis Imperfecta, Rickets and Other Bony Fragility States

This section gives an overview of radiological findings in bony fragility states, with a special focus on osteogenesis imperfecta (OI) and rickets. Conventional radiological assessment of bone density is inaccurate and imprecise and only reliably detects severe osteopaenia. However, other aspects of bone structure and morphology can be assessed, and it is possible to distinguish between osteopaenic and osteomalacic states. OI is a heterogeneous group of disorders of type 1 collagen formation and processing that are characterised by varying degrees of bony fragility, with presentations varying from perinatal lethality to asymptomatic. Radiological diagnosis of severe forms is usually straightforward, but that of milder disease may be challenging because specific features are often absent. However, a multidisciplinary approach is usually successful. Features of OI, including Wormian bones, skull base deformities, vertebral involvement and long bone fractures and deformities, are reviewed in this section. Rickets is best defined as a disorder of the growth plate characterised by the impaired apoptosis of hypertrophied chondrocytes. Vitamin D deficiency is a common cause of rickets. The patho-anatomical basis of radiological findings in rickets is reviewed and illustrated. Rickets is frequently accompanied by hyperparathyroidism and osteomalacia. Rickets used to be classified as calciopaenic or phosphopaenic but is now referred to as parathyroid hormone or fibroblast growth factor 23 mediated, respectively [1]. The radiological features of the two forms are reviewed.

Identification of two novel mutations in the PHEX gene in Chinese patients with hypophosphatemic rickets/osteomalacia

Objective

X-linked dominant hypophosphatemia (XLH) is the most prevalent form of inherited rickets/osteomalacia in humans. The aim of this study was to identify PHEX gene mutations and describe the clinical features observed in 6 unrelated Chinese families and 3 sporadic patients with hypophosphatemic rickets/osteomalacia.

Methods

For this study, 45 individuals from 9 unrelated families of Chinese Han ethnicity (including 16 patients and 29 normal phenotype subjects), and 250 healthy donors were recruited. All 22 exons and exon-intron boundaries of the PHEX gene were amplified by polymerase chain reaction (PCR) and directly sequenced.

Results

The PHEX mutations were detected in 6 familial and 3 sporadic hypophosphatemic rickets/osteomalacia. Altogether, 2 novel mutations were detected: 1 missense mutation c.1183G>C in exon 11, resulting in p.Gly395Arg and 1 missense mutation c.1751A>C in exon 17, resulting in p.His584Pro. No mutations were found in the 250 healthy controls.

Conclusions

Our study increases knowledge of the PHEX gene mutation types and clinical phenotypes found in Chinese patients with XLH, which is important for understanding the genetic basis of XLH. The molecular diagnosis of a PHEX genetic mutation is of great importance for confirming the clinical diagnosis of XLH, conducting genetic counseling, and facilitating prenatal intervention, especially in the case of sporadic patients.

Clinician approach to diagnosis of stress fractures including bisphosphonate-associated fractures

Stress fractures are repetitive strain injuries that occur in normal bones and in abnormal bones. Stress fractures share many features in common but differences depend on the status of the underlying bone. This review article for clinicians addresses aspects about stress fractures with particular respect to fatigue fractures, Looser zones of osteomalacia, atypical Looser zones, atypical femoral fractures associated with bisphosphonate therapy and stress fractures in Paget's disease of bone.

Tumor localization and biochemical response to cure in tumor-induced osteomalacia

Tumor-induced osteomalacia (TIO) is a rare disorder of phosphate wasting due to fibroblast growth factor-23 (FGF23)-secreting tumors that are often difficult to locate. We present a systematic approach to tumor localization and postoperative biochemical changes in 31 subjects with TIO. All had failed either initial localization, or relocalization (in case of recurrence or metastases) at outside institutions. Functional imaging with ¹¹¹Indium-octreotide with single photon emission computed tomography (octreo-SPECT or SPECT/CT), and ¹⁸fluorodeoxyglucose positron emission tomography/CT (FDG-PET/CT) were performed, followed by anatomic imaging (CT, MRI). Selective venous sampling (VS) was performed when multiple suspicious lesions were identified or high surgical risk was a concern. Tumors were localized in 20 of 31 subjects (64.5%). Nineteen of 20 subjects underwent octreo-SPECT imaging, and 16 of 20 FDG-PET/CT imaging. Eighteen of 19 (95%) were positive on octreo-SPECT, and 14 of 16 (88%) on FDG-PET/CT. Twelve of 20 subjects underwent VS; 10 of 12 (83%) were positive. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were as follows: sensitivity = 0.95, specificity = 0.64, PPV = 0.82, and NPV = 0.88 for octreo-SPECT; sensitivity = 0.88, specificity = 0.36, PPV = 0.62, and NPV = 0.50 for FDG-PET/CT. Fifteen subjects had their tumor resected at our institution, and were disease-free at last follow-up. Serum phosphorus returned to normal in all subjects within 1 to 5 days. In 10 subjects who were followed for at least 7 days postoperatively, intact FGF23 (iFGF23) decreased to near undetectable within hours and returned to the normal range within 5 days. C-terminal FGF23 (cFGF23) decreased immediately but remained elevated, yielding a markedly elevated cFGF23/iFGF23 ratio. Serum 1,25-dihydroxyvitamin D₃ (1,25D) rose and exceeded the normal range. In this systematic approach to tumor localization in TIO, octreo-SPECT was more sensitive and specific, but in many cases FDG-PET/CT was complementary. VS can discriminate between multiple suspicious lesions and increase certainty prior to surgery. Sustained elevations in cFGF23 and 1,25D were observed, suggesting novel regulation of FGF23 processing and 1,25D generation.

Hypophosphatemic osteomalacia induced by low-dose adefovir therapy: focus on manifestations in the skeletal system and literature review

Osteomalacia is a metabolic bone disease that leads to softening of the bones and can be caused by hypophosphatemia. Large clinical studies of low-dose adefovir dipivoxil (adefovir) have found no evidence of renal tubular dysfunction leading to hypophosphatemia after 48 weeks of treatment. We report two cases of low-dose adefovir-induced hypophosphatemic osteomalacia that initially presented with diffuse musculoskeletal pain. The first patient was a 62-year-old man with a 2-year history of bone pain involving the dorsal mid-thorax, lower anterior chest wall, right sacroiliac joint area, and both knees. The patient had been receiving adefovir for 5 years before confirmation of hypophosphatemia and urinary phosphate wasting. Bone scintigraphy revealed multifocal lesions including multiple ribs, costochondral junctions, costovertebral junctions, sacrum, both posterior iliac bones, both proximal tibia, right calcaneus, and the left second metatarsophalangeal joint area, which were suggestive of metabolic bone disorder. Bone pain was significantly reduced within 3 months after supplementation with phosphate and calcitriol. The second patient was a 54-year-old male who presented with an 18-month history of severe bone pain of the right medial knee and low back. The patient had been taking adefovir for approximately 40 months before the development of bone pain. Laboratory data revealed hypophosphatemia and vitamin D deficiency. Bone scintigraphy showed increased uptake in bilateral ribs, sternum, both scapulae, both costovertebral junctions, both pelvic bones, medial cortex of the right proximal femur, right proximal tibia, and the left lateral tarsal bone. The symptoms improved by changing the antiviral agent from adefovir to entecavir. Because osteomalacia often presents with diffuse bone pain, non-specific radiologic findings and non-characteristic routine serum biochemical changes, the disease can be confused with various musculoskeletal diseases and a high index of suspicion is necessary for an early diagnosis in patients receiving adefovir therapy.

Improving diagnosis of tumor-induced osteomalacia with Gallium-68 DOTATATE PET/CT

CONTEXT

Tumor-induced osteomalacia (TIO) is a rarely diagnosed disorder presenting with bone pain, fractures, muscle weakness, and moderate-to-severe hypophosphatemia resulting from fibroblast growth factor 23-mediated renal phosphate wasting. Tumors secreting fibroblast growth factor 23 are often small and difficult to find with conventional imaging.

OBJECTIVE

We studied the utility of (68)Ga-DOTA-octreotate (DOTATATE) somatostatin receptor positron emission tomography (PET)/computed tomography (CT) imaging in the diagnosis of TIO.

DESIGN AND SETTING

A multicenter case series was conducted at tertiary referral hospitals.

PATIENTS AND METHODS

Six patients with TIO diagnosed between 2003 and 2012 in Australia were referred for DOTATATE PET imaging. We reviewed the clinical history, biochemistry, imaging characteristics, histopathology, and clinical outcome of each patient.

RESULTS

Each case demonstrated delayed diagnosis despite severe symptoms. DOTATATE PET/CT imaging demonstrated high uptake and localized the tumor with confidence in each case. After surgical excision, there was resolution of clinical symptoms and serum phosphate, except in one patient who demonstrated residual disease on PET/CT. All tumors demonstrated high somatostatin receptor subtype 2 cell surface receptor expression using immunohistochemistry.

CONCLUSIONS

In patients with TIO, DOTATATE PET/CT can successfully localize phosphaturic mesenchymal tumors and may be a practical first step in functional imaging for this disorder. Serum phosphate should be measured routinely in patients with unexplained muscle weakness, bone pain, or stress fractures to allow earlier diagnosis of TIO.

Less frequent requests for In-111 pentreotide and its brothers of endocrinological interest

The somatostatin receptor scintigraphy (SRS), using octreotide radiolabelled with 111In (octreoscan, OCTs), is a consolidated diagnostic procedure in patients with neuroendocrine tumors. A higher accuracy has been demonstrated with single photon emission computed tomography-CT, while a further improvement has been obtained with positron emission tomography (PET)-CT, using somatostatin analogues radiolabeled with 68Ga, significantly increasing the number of detected lesions. Although the well-known presence of an OCTs uptake in many benign diseases, when in an active phase, the application of SRS in these patients did not find any clinical relevance yet. In this paper we discuss two fields of endocrinological interest where SRS could play a clinical role. In patients with Graves exophtalmos, the capability to differentiate between active and non-active disease can be helpful in define prognosis and therapeutic strategies. In patients with endocrine paraneoplastic syndromes (PNS), SRS can help in finding the underlying neoplasm, contributing to its characterization as premise to a therapeutic choice. The possible role of a surgery guided by OCTs is also explained and suggested. The incremental value of PET-CT with Ga-68 peptides is hypothesized to reduce the number of unknown neoplastic lesions frequently present in patients with PNS.

Osteodystrophy in celiac disease: ultimate complications and possible treatment

Hypovitaminosis D and its consequences are significant complications in the course of untreated celiac disease (CD). We report a case that illustrates the natural evolution of osteomalacia in an adult patient with untreated CD and his response to vitamin D supplementation. In patients with complicated CD and hypovitaminosis D, vitamin D-2 replacement in high enough doses is important to improving functional performance and for the treatment of osteomalacia.

Alkaline phosphatase in women with osteoporosis

Altogether 15 partially independent measurements of bone mass in 100 women with clinical and roentgenological signs of osteoporosis were correlated to the alkaline phosphatase activities of the same individuals. There was a slight but significant negative correlation indicating an increasing alkaline phosphatase activity with decreasing bone mass. This correlation was not caused by interaction of age. There was no correlation or morphological signs of osteomalacia. The changes could not be explained by fractures. It is suggested that a slight increase in the alkaline phosphatase activity in women with a more severe osteoporosis is related to bone resorption.

Imaging of metabolic bone diseases

Bone scintigraphy and X-ray are complementary in the assessment of Paget's disease. Whereas bone scintigraphy allows visualization of the whole skeleton and 'hot spots', X-ray enables visualization of more detailed images of the pagetic bone lesion. X-ray may be invaluable in the diagnosis of osteomalacia, especially in children. As osteomalacia is characterized by impaired bone mineralization, the use of bone density measures may lead to misinterpretation of the condition as osteoporosis. Dual-energy X-ray absorptiometry at the femoral neck is the 'gold standard' for the assessment of osteoporosis. However, all devices are useful to predict the risk of fracture. In the future, high-resolution computer tomography and magnetic resonance imaging may become valuable clinical tools, capturing the architectural aspect of bone strength and improving fracture prediction models.

Occult nasal sinus tumours causing oncogenic osteomalacia

Oncogenic osteomalacia (OOM) is a rare but curable cause of metabolic bone disease. We report 9 patients with OOM, including 2 patients with occult nasal sinus tumours and 1 in whom a progressive increase in the post-operative FGF23 level heralded the development of metastatic pulmonary disease. The median duration of symptoms before definitive surgical treatment was 6 years, and in one patient was more than 10 years. This series demonstrates that careful imaging of the nasal sinuses should be part of the work-up of cases of oncogenic osteomalacia, that serum FGF23 can be helpful in both diagnosis and monitoring treatment outcomes, and emphasizes that serum phosphate should be measured in patients with metabolic bone disease and/or unexplained musculoskeletal symptoms.

[Anticonvulsant induced metabolic disorder--case report]

Osteomalacia, metabolic bone disease in the adults, is disorder in which mineralization of the organic matrix of the skeleton is defective. This disorder is caused by a number of different conditions associated with alterations of vitamin D metabolism. Anticonvulsant therapy can also cause the development of osteomalacia due to alteration of vitamin D metabolism inducing hepatic mycrosomal enzymes, inhibiting 25-hydroxilation of vitamin D. They also inhibit intestinal calcium transport and bone mineral mobilization, independent of effects on vitamin D metabolism. This paper presents a patient who was unable to walk due to anticonvulsants induced osteomalacia. Anticonvulsant use has been implicated as a cause of bone disease for more than 30 years but there is no official recommendation for calcium and vitamin D therapy in anticonvulsant treated individuals.

Fibrogenesis imperfecta ossium: MR imaging of the axial and appendicular skeleton and correlation with a unique radiographic appearance

We describe a distinctly unusual MR appearance of the cancellous bone never before described in a patient with biopsy-proven fibrogenesis imperfecta ossium.

Clinical and bone density outcomes of tumor-induced osteomalacia after treatment

OBJECTIVE

To report the outcomes of tumor-induced osteomalacia after treatment, particularly related to recovery of bone mass.

METHODS

We review the clinical course of a 61-year-old man extremely debilitated from multiple fractures and neuromuscular weakness due to tumor-induced osteomalacia and report the changes in biochemical markers and bone density after removal of the causative neoplasm.

RESULTS

At the time of diagnosis, the patient's serum phosphorus and 1,25 dihydroxyvitamin D levels were depressed, and his fibroblast growth factor-23 level was markedly elevated. These values normalized 2 days after surgery and remained within their respective reference ranges 4 and 12 months after resection of a mesenchymal tumor. Lumbar bone density values (T-scores) were 0.445 g/cm2 (-5.9) preoperatively, 0.939 g/cm2 (-1.4) 4 months after surgery, and 1.152 g/cm2 (0.7) 12 months after surgery. Left femoral neck values at the same time points were 0.525 g/cm2 (-3.0), 1.035 g/cm2 (-0.8), and 1.184 g/cm2 (1.9). Ultra-distal radius values at the same time points were 0.128 g/cm2 (-7.0), 0.191 g/cm2 (-5.9), and 0.259 g/cm2 (-4.8). In addition, he recovered neuromuscular function and was able to leave his wheelchair.

CONCLUSION

Tumor-induced osteomalacia can be an extremely debilitating disease. With successful localization, identification, and resection of the neoplasm, bone mass and physical function can recover.

Pseudofracture of the neck of femur secondary to osteomalacia

Nutritional osteomalacia is a metabolic bone disorder common among the Asian female immigrant population in the United Kingdom. We describe the case of a female of Asian origin, who was found to have a unilateral undisplaced pseudofracture of the neck of the femur during pregnancy. Although not operated on the fracture was treated successfully with calcium and vitamin D supplement therapy. Within one month of treatment, the bone pain subsided and she was able to bear full weight. Subsequent radiological follow-up showed the pseudofracture to have healed sufficiently with no evidence of avascular necrosis.

There should be a high index of suspicion of this disease, particularly among Asian patients presenting with persistent and non-specific musculoskeletal pain.

Osteomalacia and secondary hyperparathyroidism after kidney transplantation: Relationship to vitamin D deficiency

Secondary hyperparathyroidism is highly prevalent in patients with end-stage renal disease. After successful kidney transplantation, however, parathyroid glands gradually involute to normal size with subsequent normalization of intact parathyroid hormone (PTH), serum calcium, and phosphorous concentrations. This report describes a 48-year-old diabetic end-stage renal disease patient who underwent a successful cadaveric kidney transplant. Serum calcium and phosphorous concentrations normalized within 6 months. Three years later, he presented with complaints of proximal muscle weakness that was progressively worsening. Physical examination revealed temporal wasting and proximal muscle weakness. Detailed neurologic examination was unremarkable except for decreased vibratory sensation in both feet. Laboratory data showed stable allograft function (serum creatinine, 1.3 mg/dL), hypocalcemia, and hypophosphatemia with markedly elevated alkaline phosphatase level (726 IU/L) and intact PTH level (947 pg/mL). Further laboratory evaluation revealed poor nutritional status and severe deficiency of 25(OH)D (4.0 ng/mL). Past medical history included remote episodes of acute pancreatitis due to prior alcohol abuse. Computed tomography of the abdomen showed calcific atrophic pancreas, and steatorrhea was confirmed on stool studies. Decreased bone mineral density was noted by computed tomography bone density scan. Secondary hyperparathyroidism and osteomalacia had developed due to severe vitamin D deficiency, occurring as a result of previously unrecognized, minimally symptomatic pancreatic exocrine insufficiency. Treatment with vitamin D, calcium, and pancreatic enzyme replacement led to remarkable resolution of clinical symptoms and secondary hyperparathyroidism (intact PTH, 65 pg/mL after therapy) and resulted in significant improvement in bone mineralization. Factors associated with vitamin D deficiency in the chronic kidney disease and post-transplant patient population are reviewed.

Oncogenic osteomalacia: exact tumor localization by co-registration of positron emission and computed tomography

In oncogenic osteomalacia, the causative tumor is almost always difficult to find. A novel diagnostic approach is presented that facilitates a precise and rapid localization of the associated lesion by PET-CT co-registration using the radiotracer (68)Ga-DOTANOC.

INTRODUCTION

Oncogenic osteomalacia (OOM) is an uncommon disorder characterized by hyperphosphaturia, hypophosphatemia, decreased vitamin D(3) serum levels, and osteomalacia. The paraneoplastic syndrome is exclusively driven by a small somatostatin receptor (sst)-positive tumor that produces phosphatonins, proteins that cause renal phosphate loss. OOM can be cured completely on tumor removal. However, the exact tumor localization is the most challenging step, because the lesion is notoriously difficult to detect by common imaging techniques.

MATERIALS AND METHODS

A 60-year-old woman complained of severe pain in her back and chest wall, muscle weakness, and reduced physical activity for >1 year. She suffered a metatarsal fracture and presented with hyperphosphaturia and hypophosphatemia. OOM was suspected, and a meticulous search for the tumor was initiated by conventional imaging techniques, sst-mediated imaging using (111)In-octreotide scintigraphy, and (68)Ga-DOTANOC-based positron emission tomography (PET)-CT co-registration. (68)Ga-DOTANOC is a novel radiopharmaceutical compound in which the somatostatin analog octreotide is modified at position 3, chelated with DOTA, and complexed with (68)Gallium. (68)Ga-DOTANOC has an improved affinity to sst2 and sst5 relative to other radiopeptides.

RESULTS

Whereas common imaging techniques such as CT failed to localize the tumor, (111)In-octreotide scintigraphy was able to detect the lesion, but only PET-CT using (68)Ga-DOTANOC revealed the exact tumor localization in the right femoral head. On tumor resection, the well being of the patient improved significantly, and biochemical parameters returned to normal.

CONCLUSIONS

(68)Ga-DOTANOC-based PET-CT is a novel and powerful approach to detect sst-positive tumors in a timely manner and to provide highly resolved images facilitating the development of a therapeutic strategy.