Cervical spinal cord compression attributable to a calcified intervertebral disc in a patient with X-linked hypophosphatemic rickets: case report and review of the literature

Risk factors for the development of degenerative cervical myelopathy: a review of the literature

Degenerative cervical myelopathy (DCM) encompasses various pathological conditions causing spinal cord (SC) impairment, including spondylosis (multiple level degeneration), degenerative disc disease (DDD), ossification of the posterior longitudinal ligament (OPLL), and ossification of the ligamentum flavum (OLF). It is considered the most common cause of SC dysfunction among the adult population. The degenerative phenomena of DDD, spondylosis, OPLL and OLF, is likely due to both inter-related and distinct factors. Age, cervical alignment, and range of motion, as well as congenital factors such as cervical cord-canal mismatch due to congenital stenosis, Klippel-Feil, Ehler-Danlos, and Down syndromes have been previously reported as potential factors of risk for DCM. The correlation between some comorbidities, such as rheumatoid arthritis and movement disorders (Parkinson disease and cervical dystonia) and DCM, has also been reported; however, the literature remains scare. Other patient-specific factors including smoking, participation in contact sports, regular heavy load carrying on the head, and occupation (e.g. astronauts) have also been suggested as potential risk of myelopathy development. Most of the identified DCM risk factors remain poorly studied however. Further researches will be necessary to strengthen the current knowledge on the subject, especially concerning physical labors in order to identify patients at risk and to develop an effective treatment strategy for preventing this increasing prevalent disorder.

Adult rheumatologic features, treatment and complications of X-linked hypophosphatemia

X-linked hypophosphatemia (XLH) is a rare genetic phosphate disorder caused mainly by PHEX mutations. Unlike for children, knowledge of the disease's manifestations in adults is limited. Musculoskeletal symptoms are the main feature of the disease in young adults associated with a heavy burden on patients' life. They include fractures and pseudofractures, pain, joint stiffness, osteoarthritis, enthesopathies, and muscle weakness, eventually leading to impaired quality of life. Conventional treatment with phosphate supplements and vitamin D analogs is indicated in symptomatic patients. Appropriate rehabilitation is also a key to the management of the disease to improve physical function and decrease pain, stiffness, and fatigue. Regarding the incidence and consequences of musculoskeletal features in XLH, all patients should be assessed by a bone disease specialist and, if necessary, managed by a multidisciplinary team.

Skeletal Fluorosis With Thoracic Myelopathy: A Report of 2 Cases

BACKGROUND

To report 2 different presentations of thoracic myelopathy with ossification of ligamantum flavum (OLF) due to fluorosis.

METHODS

Two females presented with thoracic myelopathy secondary to spinal stenosis with OLF due to fluorosis. On examination, the first patient had a grade 4 power in both lower limbs with altered sensation below L1 dermatome. She had segmental OLF on magnetic resonance imaging and computed tomography and was treated with posterior thoracic laminectomy and recovered well. The second patient had a history of a prior thoracic laminectomy at another institution and presented with paraplegia with bladder involvement. Radiological investigations revealed a 3-column injury at the level of D8/D9. This patient was treated with decompression and stabilization.

RESULTS

The first patient recovered neurologically and regained independent ambulation while the second patient had a reduction in spasticity but no recovery of power or bladder function.

CONCLUSION

Different presentations and causes of myelopathy due to OLF should be recognized and treated. An unstable injury is very rare and should not be missed.

Consensus Recommendations for the Diagnosis and Management of X-Linked Hypophosphatemia in Belgium

X-linked hypophosphatemia (XLH) is the most common genetic form of hypophosphatemic rickets and osteomalacia. In this disease, mutations in the PHEX gene lead to elevated levels of the hormone fibroblast growth factor 23 (FGF23), resulting in renal phosphate wasting and impaired skeletal and dental mineralization. Recently, international guidelines for the diagnosis and treatment of this condition have been published. However, more specific recommendations are needed to provide guidance at the national level, considering resource availability and health economic aspects. A national multidisciplinary group of Belgian experts convened to discuss translation of international best available evidence into locally feasible consensus recommendations. Patients with XLH may present to a wide array of primary, secondary and tertiary care physicians, among whom awareness of the disease should be raised. XLH has a very broad differential-diagnosis for which clinical features, biochemical and genetic testing in centers of expertise are recommended. Optimal care requires a multidisciplinary approach, guided by an expert in metabolic bone diseases and involving (according to the individual patient's needs) pediatric and adult medical specialties and paramedical caregivers, including but not limited to general practitioners, dentists, radiologists and orthopedic surgeons. In children with severe or refractory symptoms, FGF23 inhibition using burosumab may provide superior outcomes compared to conventional medical therapy with phosphate supplements and active vitamin D analogues. Burosumab has also demonstrated promising results in adults on certain clinical outcomes such as pseudofractures. In summary, this work outlines recommendations for clinicians and policymakers, with a vision for improving the diagnostic and therapeutic landscape for XLH patients in Belgium.

Outcome of adult patients with X-linked hypophosphatemia caused by PHEX gene mutations

X-linked hypophosphatemia (XLH) is the most common monogenic disorder causing hypophosphatemia. This case-note review documents the clinical features and the complications of treatment in 59 adults (19 male, 40 female) with XLH. XLH is associated with a large number of private mutations; 37 different mutations in the PHEX gene were identified in this cohort, 14 of which have not been previously reported. Orthopaedic involvement requiring surgical intervention (osteotomy) was frequent. Joint replacement and decompressive laminectomy were observed in those older than 40 years. Dental disease (63%), nephrocalcinosis (42%), and hearing impairment (14%) were also common. The rarity of the disease and the large number of variants make it difficult to discern specific genotype-phenotype relationships. A new treatment, an anti-FGF23 antibody, that may affect the natural history of the disease is currently being investigated in clinical trials.

Cervical dural calcification and cervical myelopathy in X-linked hypophosphataemic rickets: a case report and review of the literature

X-linked hypophosphataemic rickets (XLHR) is a genetic disorder resulting from a genetic mutation in the PHEX gene. This may cause ossification of soft tissue structures risking spinal cord compression. We present the first known case of cervical dural calcification secondary to XLHR to cause myelopathic symptoms due to cord compression.

Extensive ossification of the paraspinal ligaments in a patient with vitamin D-resistant rickets: Case report with literature review

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This is the case of a 64-year-old woman with VDRR and extensive spinal ossification.

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This case was followed up for over 30 years.

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Imaging studies demonstrated fusion of the entire spine below the C2 vertebra.

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Mobility at the craniovertebral junction caused C1-level spinal cord compression.

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The pathology mimicked ankylosing spondylitis.

Introduction

Ectopic ossification of the spinal ligaments is not uncommon in patients with Vitamin D-resistant rickets (VDRR), but the long-term consequences of this condition have not been reported.

Presentation of case

The case was a 65-year-old female with VDRR who reported progressive weakness of the upper extremities, difficulty walking, neck pain, and numbness in the left arm. Imaging studies demonstrated cord compression with ectopic ossification at the rim of the occipital bone and OPLL at C1 level. Ankylosis of the whole spine below the C2 vertebra was also noted with preserved mobility only at the craniovertebral junction.

Discussion

Our report showed that ectopic ossification of the spinal ligament can result in ankylosis of the entire spine in patients with VDRR. In such patients, the segments with remaining mobility are considered to be at high risk of developing myelopathy due to increased stress at the junction.

Conclusion

The present case underscores the importance of providing long-term follow-up in VDRR patients presenting with ectopic ossification of the spinal ligaments. In particular, physicians should pay close attention to the possibility of myelopathy in any segments with preserved mobility.

Minimally Invasive Surgical Management of Thoracic Ossification of the Ligamentum Flavum Associated with X-linked Hypophosphatemia

BACKGROUND

X-linked hypophosphatemia (XLH) is the most common inherited form of renal phosphate wasting and inherited rickets. Patients have hyperplasia of fibrochondrocytes in tendons and ligaments, causing the structures to thicken and calcify. Thickening of the lamina, hypertrophy of facet joints, and calcification of spinal ligaments are sequelae of this condition and can result in central or foraminal stenosis that compresses nerve roots or the spinal cord. We present a case of XLH with calcification of the ligamentum flavum in which the patient was operated on using minimally invasive posterior decompression.

CASE DESCRIPTION

A 49-year-old man with a history of XLH presented to our emergency department with symptomatic myelopathy from multilevel thoracic stenosis. Radiographically, the calcified ligamentum flavum appeared to be the cause of the stenosis at various levels. The patient underwent a posterior decompression at the levels of compression, T4-T5, T8-T9, T9-T10, and T11-T12, via a minimally invasive spine surgery approach. Intraoperatively, the ligamentum flavum appeared to be both calcified and the source of spinal compression. Postoperatively, the patient experienced neurologic and radiographic improvement.

CONCLUSION

Patients with a history of XLH and multilevel symptomatic spine stenosis can be treated successfully and safely with a minimally invasive posterior decompression.

Chiari malformation, syringomyelia and bulbar palsy in X linked hypophosphataemia

X linked hypophosphataemia (XLH) is a rare condition with numerous musculoskeletal complications. It may mimic other more familiar conditions, such as vitamin D deficiency, ankylosing spondylitis or diffuse idiopathic skeletal hyperostosis. We describe two cases with Chiari type 1 malformations and syringomyelia, neither of which is well recognised in XLH. The first presented late with the additional complications of spinal cord compression, pseudofracture, renal stones and gross femoroacetabular impingement requiring hip replacement. The second also had bulbar palsy; the first case to be described in this condition, to the best of our knowledge. We wish to raise awareness of the important neurological complications of syringomyelia, Chiari malformation, spinal cord compression and bulbar palsy when treating these patients. We also wish to draw attention to the utility of family history and genetic testing when making the diagnosis of this rare but potentially treatable condition.

Cervical ossification of posterior longitudinal ligament in x-linked hypophosphatemic rickets revealing homogeneously increased vertebral bone density

There is no report that describes in detail the radiological and intraoperative findings of rickets with symptomatic cervical ossification of the posterior longitudinal ligament. Here, we describe a case of X-linked hypophosphatemic rickets with cervical ossification of the posterior longitudinal ligament presenting unique radiological and intraoperative findings. The patient presented progressive tetraparesis. Magnetic resonance imaging studies revealed severe cervical spinal cord compression caused by ossification of the posterior longitudinal ligament. Computed tomography scans revealed homogeneously increased vertebral bone density. An expansive laminoplasty was performed. At surgery, homogeneously hard lamina bone was burdened in drilling and opening of the laminae. The patient's neurological symptoms were improved postoperatively. Bony fusion of the hinges occurred postoperatively. Therefore, expansive laminoplasty could be performed for symptomatic cervical ossification of the posterior longitudinal ligament with X-linked hypophosphatemic rickets. However, unusual bone characters should be taken into consideration for careful operation during surgery.

Mineralizing enthesopathy is a common feature of renal phosphate-wasting disorders attributed to FGF23 and is exacerbated by standard therapy in hyp mice

We have previously confirmed a paradoxical mineralizing enthesopathy as a hallmark of X-linked hypophosphatemia. X-linked hypophosphatemia is the most common of the phosphate-wasting disorders mediated by elevated fibroblast growth factor 23 (FGF23) and occurs as a consequence of inactivating mutations of the PHEX gene product. Despite childhood management of the disease, these complications of tendon and ligament insertion sites account for a great deal of the disease's morbidity into adulthood. It is unclear whether the enthesopathy occurs in other forms of renal phosphate-wasting disorders attributable to high FGF23 levels. Here we describe two patients with autosomal recessive hypophosphatemic rickets due to the Met1Val mutation in dentin matrix acidic phosphoprotein 1 (DMP1). In addition to the biochemical and skeletal features of long-standing rickets with elevated FGF23 levels, these individuals exhibited severe, debilitating, generalized mineralized enthesopathy. These data suggest that enthesophytes are a feature common to FGF23-mediated phosphate-wasting disorders. To address this possibility, we examined a murine model of FGF23 overexpression using a transgene encoding the secreted form of human FGF23 (R176Q) cDNA (FGF23-TG mice). We report that FGF23-TG mice display a similar mineralizing enthesopathy of the Achilles and plantar facial insertions. In addition, we examined the impact of standard therapy for phosphate-wasting disorders on enthesophyte progression. We report that fibrochondrocyte hyperplasia persisted in Hyp mice treated with oral phosphate and calcitriol. In addition, treatment had the untoward effect of further exacerbating the mineralization of fibrochondrocytes that define the bone spur of the Achilles insertion. These studies support the need for newer interventions targeted at limiting the actions of FGF23 and minimizing both the toxicities and potential morbidities associated with standard therapy.

Phenotype presentation of hypophosphatemic rickets in adults

Hypophosphatemic rickets (HR) is a group of rare disorders caused by excessive renal phosphate wasting. The purpose of this cross-sectional study of 38 HR patients was to characterize the phenotype of adult HR patients. Moreover, skeletal and endodontic severity scores were defined to assess possible gender differences in disease severity in patients with genetically verified X-linked HR. Compared to normal reference data, i.e., z = 0, HR patients had significantly lower final height, with a mean difference in z-score of -1.9 (95% CI -2.4 to -1.4, P < 0.001). Compared to paired z-scores of final height, z-scores of leg length were significantly lower and those of sitting height were significantly higher (P < 0.001), resulting in disproportion as indicated by the significantly elevated sitting height ratio, mean difference in z-score of 2.6 (95% CI 2.1-3.1, P < 0.001). Z-scores of head circumference (median 1.4, range -0.4 to 5.5, P < 0.001) and z-scores of bone mineral density (BMD) of the lumbar spine (median 1.9, range -1.5 to 8.6, P < 0.001) were significantly elevated compared to normal reference data. The relative risk (RR) of fracture was reduced (RR = 0.34, 95% CI 0.20-0.57, P < 0.001). The skeletal severity score tended to be higher in males compared to females (P = 0.07), and no gender difference in endodontic severity was found. In conclusion, adult HR patients were characterized by short stature and were disproportioned. They had elevated BMD of the lumbar spine and a reduced risk of fractures. We found a tendency for males to be more severely affected than females.

Hormones and growth factors in the pathogenesis of spinal ligament ossification

Ossification of the spinal ligaments (OSL) is a pathologic condition that causes ectopic bone formation and subsequently results in various degrees of neurological deficit, but the etiology of OSL remains almost unknown. Some systemic hormones, such as 1,25-dihydroxyvitamin D, parathyroid hormone (PTH), insulin and leptin, and local growth factors, such as transforming growth factor-beta (TGF-beta), and bone morphogenetic protein (BMP), have been studied and are thought to be involved in the initiation and development of OSL. This review article summarizes these studies, delineates the possible mechanisms, and puts forward doubts and new questions. The related findings from studies of genes and target cells in the ligament of OSL are also discussed. Although these findings may be helpful in understanding the pathogenesis of OSL, much more research needs to be conducted in order to investigate the nature of OSL.

Ossification of the ligamentum flavum as a result of fluorosis causing myelopathy: report of two cases

OBJECTIVE AND IMPORTANCE

Ossification of the ligamentum flavum (OLF) is increasingly being recognized as a cause of myeloradiculopathy. However, the cause of such OLF has been identified only occasionally. The purpose of this case report is to highlight one more cause of OLF causing myelopathy.

CLINICAL PRESENTATION

Two middle-aged men residing in an area endemic for fluorosis presented with the insidious onset of myelopathy. Clinical examination revealed evidence of thoracic cord compression in both patients. Plain x-rays revealed markedly increased bone density characteristic of fluorosis. Magnetic resonance imaging revealed OLF in the lower thoracic region causing cord compression (at one level in the first patient and at three consecutive levels in the second patient). Plain x-rays of the forearm revealed ossification of the interosseous membrane, which is characteristic of fluorosis.

INTERVENTION

Both patients underwent decompressive laminectomy with removal of the OLF. The laminae and ossified yellow ligaments formed one mass of bone, which was removed with rongeurs and drills. After surgery, the first patient demonstrated improvement in motor power, whereas the second patient did not demonstrate any change in neurological status.

CONCLUSION

Fluorosis should be entertained in the differential diagnosis of OLF, especially in patients from endemic areas. The magnetic resonance imaging appearance of the spine in such cases is characteristic. In properly selected cases of fluorotic myelopathy, surgery is indicated. However, the prognosis is guarded, and long-term follow-up of these patients is necessary given the nature of the underlying disease.