Department of Renal Medicine, St James's University Hospital, Leeds, UK
Keywords: lupus erythematosus; sclerotic bone disease; end-stage renal failure; tertiary hyperparathyroidism
Case
We present a patient who was diagnosed with systemic lupus erythematosus (SLE) in 1979 at the age of 19 years. Six months after presentation she developed nephrotic syndrome and was treated with prednisolone and azathioprine. However, in the following 4 years she progressed to end-stage renal failure (ESRF) and started haemodialysis. In 1984 she received a cadaveric renal transplant but underwent a transplant nephrectomy 1 month later, due to steroid-resistant rejection. In 1986, she received a second cadaveric renal transplant but returned to dialysis 2 years later due to chronic allograft nephropathy. After a brief period of time on haemodialysis she changed modality to peritoneal dialysis.
In July 1990, she complained of a 10-day history of severe right-sided neck pain radiating to the right shoulder. This was extremely painful, despite regular analgesics, and was associated with severely limited range of movement of the neck. Neurological examination was unremarkable. A skeletal survey performed 1 year previously had shown widespread erosions in the middle phalanges of all fingers and some of the terminal tufts, and calcification of the medial sclerosis type affecting arteries of the feet, hands, forearms and pelvis. Investigations showed elevated alkaline phosphatase 1983 iu/l (70300), grossly elevated parathyroid hormone (PTH) 1597 ng/l (1065), calcium 2.22 mmol/l (2.22.6), phosphate 1.27 mmol/l (0.81.3), C-reactive protein 18 mg/l (<10), and aluminium 1.15 µmol/l (acceptable level <1.9). A plain film of the cervical spine (Figure 1) showed absence of C5 vertebra. A hard neck collar was fitted and a CT-guided biopsy of the vertebrae was carried out. However, the histology specimen consisted mainly of blood and a core of fibrocartilage, muscle and fatty tissue. Stains for amyloid were negative but the tissue was inadequate for diagnosis. Our patient underwent an urgent total parathyroidectomy in August 1990. Post-operative PTH levels were 4 ng/l. A repeat film of the cervical spine performed 6 months after initial presentation is shown in Figure 2
. At this stage an orthopaedic opinion recommended it was safe to remove the collar in view of the good range of movement of the cervical spine.
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Discussion
Cervical spine involvement in patients with ESRF, especially those undergoing dialysis, can be due to a number of reasons. Renal osteodystrophy (ROD) can be seen throughout the spine, but reports of significant cervical spine involvement are uncommon. Patients typically seek treatment for pain in the thoracic or lumbar area. The classical stigmata of ROD in the vertebrae is the rugger-jersey spine which consists of bands of increased density paralleling the end-plates of the vertebral body and a band of radiolucency in the centre of the body [1]. Components of ROD include hyperparathyroidism, osteoporosis and osteomalacia. Hyperparathyroidism can lead to brown tumours (osteoclastomas), which appear as cysts in bone [1]. They are cavities in bone in which there is excessive osteoclastic resorption, fibrous tissue, necrosis and liquefaction. They can occur anywhere in the skeleton and may expand bone. When the cervical spine is involved in ROD, the need for surgical intervention for instability in the spine seldom arises. However, in 1993, Nair et al. [2] reported six patients treated over the previous 3 years who demonstrated cervical instability and cord compression, all of which required surgical intervention. These patients had been on haemodialysis for between 4 and 12 years. It is also of note that two patients had both ROD and superimposed osteomyelitis.
Infection should be included in the differential diagnosis of erosive changes on plain X-rays of the spine, especially due to the increased risk of infection in haemodialysis patients. Cervical vertebrae are the least common sites of infection in vertebral osteomyelitis and when it does occur, contiguous spread must also be considered [3]. This usually results in paravertebral or epidural masses. The latter are best identified on MRI and a high erythrocyte sedimentation rate and/or CRP should help distinguish infective discitis/osteomyelitis from destructive spondyloarthropathy (DSA).
DSA is another cause of erosive spondyloarthropathy in patients on long-term haemodialysis and usually involves the middle to lower cervical spine [4]. Spinal cord compression has been described but is rare [57]. MRI is useful in establishing a differential diagnosis with infection. The aetiology of DSA is debated but suggested causes are hyperparathyroidism, crystal deposition disease (apatite crystals) [1], amyloid (ß2-microglobulin deposition) [6], aluminium overload, ligamentous laxity, and neuropathy (in diabetic patients). Hyperparathyroidism appears to be the most important contributing factor. Parathyroidectomy is indicated to halt the progression of the erosive process.
In our patient, it is difficult to be certain whether there was an initial osteoclastoma preceding the complete destruction of C5 vertebra or whether this could be attributed entirely to DSA. In either case, however, the underlying pathogenesis was hyperparathyroidism, and an urgent total parathyroidectomy, with subsequent alfacalcidol supplementation, was the mainstay of treatment. This resulted in a stabilization of the lesion and her symptoms and was followed by ossification with maintenance of satisfactory cervical spine function.
Notes
Correspondence and offprint requests to: A. M. Davison, Department of Renal Medicine, St James's University Hospital, Beckett Street, Leeds LS9 7TF, UK. E-mail: alex.davison{at}leedsth.nhs.uk
References