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 Table of Contents  
Year : 2022  |  Volume : 19  |  Issue : 2  |  Page : 75-78

Monostotic paget's disease of the thoracic vertebra masquerading as metastasis

1 Department of Spine Surgery, Baby Memorial Hospital, Kozhikode, Kerala, India
2 Department of Orthopaedics, Baby Memorial Hospital, Kozhikode, Kerala, India

Date of Submission30-Oct-2022
Date of Acceptance11-Nov-2022
Date of Web Publication09-Feb-2023

Correspondence Address:
Amalraj P Nair
Department of Orthopaedics, Baby Memorial Hospital, Kozhikode, Kerala
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/joasis.joasis_36_22

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Paget's disease (PD) is a metabolic bone disease characterized by abnormal bone remodeling. The bone passes through different phases depending up on the osteoblast and osteoclast activity. The prevalence of the disease is rare in the Asian population. The vertebrae are the second-most commonly affected site. It may mimic metastatic spine lesions clinically and radiologically. X-ray, computed tomography (CT) scan, magnetic resonance imaging (MRI), and bone/positron emission tomography scan are used in aid of diagnosing the disease. The confirmation is by biopsy. Complications of the disease range from back pain to neurological deficits and malignant transformation. Here, we present a case of PD of thoracic vertebrae which is a rare entity in the Indian subcontinent. The patient presented with back pain and neurogenic claudication. MRI with CT correlation showed suspicion of vertebral malignancy and a biopsy was done which showed PD. He was treated with posterior stabilization using pedicle screws and rods. The importance of this case report is to present a case which is rare in the Indian population and to make awareness regarding PD as one of the differentials in vertebral lesions.

Keywords: Monostotic, Paget's disease, posterior stabilization, vertebra

How to cite this article:
Pillai SS, Nair AP, Arjun K, Neerngat J. Monostotic paget's disease of the thoracic vertebra masquerading as metastasis. J Orthop Assoc South Indian States 2022;19:75-8

How to cite this URL:
Pillai SS, Nair AP, Arjun K, Neerngat J. Monostotic paget's disease of the thoracic vertebra masquerading as metastasis. J Orthop Assoc South Indian States [serial online] 2022 [cited 2023 Mar 27];19:75-8. Available from: https://www.joasis.org/text.asp?2022/19/2/75/369410

  Introduction Top

Paget's disease (PD) also known as osteitis deformans is one of the most common metabolically active bone diseases. It is common in the European population and is less common in the Asian and African populations. PD can be monostotic or polystotic.

The most common affected site is the pelvis, followed by the spine.[1],[2] In PD, there is abnormal functioning of osteoclast and osteoblast characterized by deranged bone remodeling. This type of remodeling causes the bone to initially expand and further leading to the stage of collapse. Back pain is the most common symptom and the site depends upon the involved vertebrae. There are several complications for PD such as compression fracture, spinal stenosis, facet joint arthropathy, spondylolysis, and spondylolisthesis. PD can also affect extra-osseous soft tissues.

The imaging manifestation of PD varies depending on the different stages. X-ray, computed tomography (CT) scan, magnetic resonance imaging (MRI), and bony scan/positron emission tomography (PET) CT show various patterns based on vertebral involvement and stage. As a result, PD is sometimes difficult to distinguish from vertebral malignancy through these modalities.

Medical treatment in PD includes the use of bisphosphonates. Surgical treatment in the form of posterior stabilization with or without vertebroplasty is also done. In affected vertebrae, it helps to prevent the collapse and development of neurological deficits. In established cases of spinal instability/collapse, it highlights as the treatment of choice. Here, we present the case of a 79-year-old male who presented with back pain where CT and MRI demonstrated suspicious of malignancy but turned out to be PD of the dorsal spine in the biopsy. The involvement of the dorsal spine in PD is a rare entity in the Asian population which also add significance to this case report.

  Case Report Top

A 79-year-old male presented with dull aching pain in the upper back for 2-week duration. The pain progressed to such a level that he found difficulty to walk. There was no history of recent trauma/fall, fever, weight loss, or any other constitutional symptoms.

The patient is a known case of hypertension and coronary artery disease who underwent coronary angioplasty and is on antiplatelet and antihypertensive therapy. The general examination was normal. A local examination of the spine did not reveal any positive findings. He did not have any neurovascular deficits.

Blood parameters were within normal limits.

Radiography of the thoracolumbar region showed no significant abnormality. MRI of the dorsolumbar spine showed marrow signal alteration appearing hypointense on the T1-weighted image and showing hyperintensity on STIR images noted involving the body, bilateral pedicles, laminae, and spinous process of D10 vertebra with an intact cord.

On correlative CT sections, the involved vertebra shows irregular lytic, sclerotic areas with no definite fractures.

Serum protein immunofixation electrophoresis was normal. Whole body PET scan revealed diffuse in homogenous increased fluorodeoxyglucose uptake in the body and the posterior elements of the D10 vertebrae with few areas of sclerosis and lytic changes and was reported likely neoplastic.

The patient was admitted and he underwent a CT-guided biopsy from the D10 vertebra. Histopathological examination showed irregular trabeculae of cortical bone with scalloping of the borders, which are rimmed by osteoclasts and osteoblasts and peritrabecular fibrosis. The findings were consistent with PD of the bone

The patient was advised surgical fixation and biopsy of the D10 vertebra in view of the circumferential involvement of the D10 vertebra and possible collapse of the vertebra.

He is advised to avoid weight bearing till the lesion is addressed.

Under general anesthesia, he underwent posterior stabilization D8, D9-D11, and D12 using polyaxial pedicle screws and titanium rods. Intraoperatively, abnormal-looking bone with bluish hue was noted in the bilateral lamina and transverse processes of D10 vertebrae. Posterior part of the transverse process was taken and sent for biopsy.

The patient was ambulated on the next postoperative day and discharged in the next 3 days.

  Discussion Top

PD is a metabolically active bone disease, first coined by James Paget in 1877. The abnormality in homeostatic control of osteoclast and osteoblast in bone remodeling is the main pathognomic behind this disease. As a result, the rate of bone turnover is imbalanced and there will be excessive bone resorption by osteoclast followed by bone formation by osteoblast. The etiology is still unclear but various authors suggest genetic predisposition as a factor. Studies showing a relationship with PD and paramyxovirus also exist. It is sometimes variously classified under infection, neoplasm, or metabolic disorder.

The disease is slightly male predominant with a ratio of 1.8:1 and is common in 5th decade of life. The most common site involved in PD is the pelvis followed by the spine, skull, femur, and tibia. Lumbar vertebrae are commonly affected. Among lumbar vertebrae, 58% of this occurs in L4 and L5. It is followed by thoracic vertebrae and cervical vertebrae. The overall prevalence of the disease is 3%–3.7% and increases with age.[3],[4] The disease incidence represents geographic variations. It is common in the UK, European, and Australian populations, whereas less common in Asians, Scandinavians, and Africans.[5]

Mutation in chromosome 1/p62 has a strong genetic composition with PD. The differentiation and activation of osteoblast in response to cytokines also arises relation of the disease with SQSTM1/p62 chromosomal abnormality apart from the above mutation.

Based on the activity of osteoblasts and osteoclast, PD passes through three phases: early lytic phase which represents osteoclasts activity, late sclerotic phase represents osteoblastic activity, and the intervening mixed phase.[6],[7] The early lytic phase can be radiologically demonstrated very well in bones such as the skull, femur, and humerus due to the low trabecular/cortex ratio and is difficult in bones such as vertebra, sacrum, and pelvis. The abnormal increased activity of osteoblasts leads to the newborn formation (apposition) in the periosteum and endosteum, whereas the osteoclastic activity predominately affecting endosteum results in bone resorption (absorption). The combination of these mechanisms gives rise to four different patterns of bone remodeling. The end result of all being the bone enlargement.

The common presentation of PD is in polyostotic form (35%–50%) than in monostotic form (<0%). Moreover, in India, monostotic vertebral PD is a rare entity.

Clinically, PD presents with back pain which may be constant, radiating pain, localized, or diffuse. The causes of pain may be due to periosteal stretching, vascular engorgement, microfractures, facet arthritis, intervertebral disc disease, overt fractures of vertebrae or sacrum, spondylolysis/-listhesis, etc. If PD results in spinal stenosis due to various mechanisms, the symptoms may be of neurological dysfunction such as sensory/motor deficits. In long weight-bearing bones such as the tibia and femur, deformity may be present. Apart from the vertebra, the involvement of the skull in PD causes neurological symptoms depending on the cranial nerves involved such as hearing loss, vertigo, and fascial nerve palsies.

Since the disease involves high bone turnover, the level of alkaline phosphatase (ALP) estimation has its own significance. The polyostotic form which has a high born turn over shows markedly increased level of ALP, whereas in the monostotic form, the level of ALP may seen on the high normal range. Vitamin D deficiency also causes a rise in ALP level and bone pain, so the assessment and Vitamin D correction should be addressed before starting the treatment. In the osteoblastic phase, there will be a rise in bone ALP and osteocalcin[8] and in the osteoclastic phase, urine examination shows raised hydroxyproline and pyridinoline.

Different radiological modalities can be used for demonstrating PD and its varying stages. In X-rays, the vertebral body expansion can be seen as an increase in anteroposterior and lateral dimensions. Usually, the earliest phase seen in X-ray is the mixed phase. The combination of apposition and absorption gives rise to “picture frame”[9] sign in the vertebra. In the advanced sclerotic phase, the involved vertebra will be denser than the normal termed as “ivory vertebra.” Metastasis, lymphoma in the spine also takes the form of the ivory vertebra, so should be aware of differentiating it from PD.

CT scan best appreciates the areas of increased density and lucent areas. The high contrast resolution and multiplanar reconstruction help in confirming the lytic phase. CT scan is also considered the best modality in assessing the neural arch involvement which is usually missed in X-rays. It also plays an important role in differentiating epidural fat ossification and epidural lipomatosis from spinal canal stenosis which is misinterpreted in MRI.

PD primarily involves bone rather than bone marrow. When secondary marrow changes occur, they can be demonstrated with MRI. It also helps in identifying the cord/root involvement, changes in anterior/posterior longitudinal ligaments, intervertebral disk, and epidural fat. In case of minimal or absent marrow involvement, MRI shows a wide spectrum of changes. Hence, MRI findings need the comparison of CT and radiographs in many instances.

Bone scintigraphy using 99-Technetium can aid in the diagnosis of PD. Its sensitivity to osteoblastic activity is high. Depending upon the involvement of the vertebral body, pedicles, and spinous process, the bone scan may appear like clover shape or heart shape. Imaging techniques such as PET and PET-CT can contribute to the differential diagnosis of PD from others disorders in the spine.

Microscopically in PD, the bony trabeculae appear thickened and irregular. Irregular blue cement lines are characteristics. Osteoblastic and osteoclastic activity is increased. Although these features are quite typical, they are not diagnostic. Pagetoid bone may be seen in various conditions including osteosarcomas and reactions to metastatic carcinoma. From the above-described things, it is clear that the clinic-radiological features of PD mimic spinal metastasis. This correlates the importance of our case report where a case suspicious of spinal malignancy turned to be PD.

Paget's bone is structurally and functionally weak. The pathological complications of vertebral involvement include back pain, spinal stenosis with neurological dysfunction, compression fracture, paravertebral swelling, facet joint arthropathy, spondylolysis/spondylolisthesis, intervertebral disc involvement, and neoplastic transformation. The incidence of neoplastic transformation represents only 7%[10] and the major transformations are of osteosarcomas.

The treatment of PD depends on the symptoms and complications. Medical treatment includes bisphosphonates and calcitonin administration. The duration depends on the stage and symptom relief. The medical treatment is indicated for pain in pagetic bone, osteolytic lesions with increased fracture risk, involvement of long bones, vertebra, skull, asymptomatic joint involvement, and patients undergoing surgery. The common drugs used are pamidronate and alendronate. It is necessary to monitor the level of ALP to understand the course of the disease. Long bones with deformity and fractures should be managed specifically.

The surgical treatment includes posterior stabilization with pedicle screws and lordotic rods with or without vertebroplasty. This is helpful in patients for reducing pain, preventing complications, and resolving neurological deficits by increasing the diameter of the foramina.

The case we reported came with complaints of back pain and neurologic claudication. The diagnosis of PD was difficult as the X-ray did not demonstrate any significant changes associated with PD. In CT and MRI, the suspicious of myeloproliferative disease/marrow infilterative process was put forward. Hence, in view of the doubtful pathology, we proceeded with CT-guided biopsy from the involved vertebra. The biopsy report showed as PD. In view of severe pain, neurologic claudication, and prevent the potential complication of the disease, we treated the patient surgically with posterior stabilization using screws and lordotic rods. The patient had significant relief in symptoms and was able to return his normal life in few weeks.

  Conclusion Top

Monostotic PD involving the spine is a rare disease in the Asian population. It is a diagnosis of exclusion. The knowledge of incidence, symptoms, pathophysiology and radiological manifestation is very important in understanding this disease. It can also cause systemic manifestations and metabolic alterations in the case where it significantly affects the bone marrow. It can mimic various pathological conditions such as myeloma, lymphoma, metastasis, vertebral osteomyelitis, or compression fractures in old age. It requires clinical, biochemical, and radiological to identify the disease and to rule out the differentials. Final confirmation of disease is by histopathological examination. The treatment depends on the symptoms and stage of the disease. Patient selection is an important criteria in treating PD. Surgical fixation is emerging as a definitive treatment as it helps in pain relief, resolves neurologic deficits, and prevents potential complications. In brief, Indian doctors should have an awareness of PD as a differential in patients presenting with vertebral lesions.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Altman RD, Brown M, Gargano F. Low back pain in Paget's disease of bone. Clin Orthop Relat Res 1987;(217):152-61.  Back to cited text no. 1
Danais S, Hadjipavlou A. Comparative scientific study of lesionsof bone and bone marrow in Paget's disease. Union Med Can 1977;106:1100-9.  Back to cited text no. 2
Collins DH. Paget's disease of bone; incidence and subclinical forms. Lancet 1956;271:51-7.  Back to cited text no. 3
Schmorl G. Über Osteitis deformans paget. Virchows Arch Pathol Anat Physiol 1932;238:694-751.  Back to cited text no. 4
Walsh JP. Paget's disease of bone. Med J Aust 2004;181:262-5.  Back to cited text no. 5
Zlatkin MB, Lander PH, Hadjipavlou AG, Levine JS. Paget disease of the spine: CT with clinical correlation. Radiology 1986;160:155-9.  Back to cited text no. 6
Lander P, Hadjipavlou A. Intradiscal invasion of Paget's disease of the spine. Spine (Phila Pa 1976) 1991;16:46-51.  Back to cited text no. 7
Alvarez L, RicOs C, Peris P, GuaNabens N, Monegal A, Pons F, et al. Components of biological variation of biochemical markers of bone turnover in Paget's bone disease. Bone 2000;26:571-6.  Back to cited text no. 8
Graham TS. The ivory vertebra sign. Radiology 2005;235:614-5.  Back to cited text no. 9
Schajowicz F, Santini Araujo E, Berenstein M. Sarcoma complicating Paget's disease of bone. A clinicopathological study of 62 cases. J Bone Joint Surg Br 1983;65:299-307.  Back to cited text no. 10


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