Departments of Medicine
1 Radiology, Chris Hani Baragwanath Hospital and University of the Witwatersrand, Johannesburg, South Africa
SIR, Systemic sclerosis (SSc) is a multisystem rheumatic disorder characterized by excessive fibrosis of the skin and visceral organs, vasculopathy and circulating autoantibodies. A wide spectrum of bone, joint and soft-tissue manifestations occur in 4697% of all SSc patients and as the presenting feature in 1265% of patients [1, 2]. Osseous resorption or osteolysis is a rare, but perhaps the most characteristic, radiographic feature of SSc. The terminal digital tufts of the phalanges are most commonly affected, but osteolysis has also been observed in other skeletal sites, including the distal radius and ulna, ribs, the mandible, the distal clavicle and cervical spine. We report a case of extensive osteolysis involving the terminal phalanges, ribs, mandible and posterior elements of the cervical spine in a patient with diffuse cutaneous SSc (dcSSc).
Ms AK, a 54-yr-old black patient with a 16-yr history of SSc, complained of progressive worsening of hand deformities, difficulty biting and chewing food, and neck pain over a 2-yr period. There were no symptoms suggestive of trigeminal neuralgia. She had previously been documented to have dcSSc, characterized by severe Raynaud's phenomenon (present throughout the year), oesophageal dysmotility, telangiectasia, calcinosis, salt and pepper depigmentation of the face and trunk, ischaemic pits of the pulp spaces of the fingers, and resorption of the terminal phalanges. There was no history of exposure to silica or any chemicals. Investigations showed that she was ANA-positive and positive for anti-topoisomerase-1 and U3 RNP (fibrillarin) antibodies. The radiographs of the hand confirmed resorption of the distal phalangeal tufts. Lung function tests revealed a restrictive pattern. A high-resolution computed tomography (CT) scan of the lungs was normal. She has been treated with omeprazole for reflux oesophagitis and a combination of nifedipine and perindopril for the Raynaud's phenomenon. In the past she had been treated for approximately 3 yr with d-penicillamine, which was stopped about 5 yr ago because of no noticeable improvement in the skin.
On examination she had extensive skin thickening with a modified Rodnan's total skin score of 18 [3]. Apart from the features noted previously, she had severe acro-osteolysis of the fingers resembling arthritis mutilans and obvious retrognathia. She was tender over the posterior aspect of the neck and there was cervical scoliosis to the left. There were no cranial nerve abnormalities or pyramidal tract signs.
Plain radiographs of the neck confirmed the scoliosis as well as extensive resorption of the posterior spinous processes. The chest radiograph showed resorption of the clavicle and ribs 2, 3, 4 and 5 bilaterally. A CT scan of the neck revealed almost 45° rotation of the bodies of the cervical vertebrae, except for C1 (Figs 1 and 2). In addition, there was variable osteolysis of the laminae of all the cervical vertebrae and mandible. The sagittal T2-weighted magnetic resonance imaging (MRI) similarly showed striking osteolysis of the posterior elements of C2C5, including the laminae and spinous processes (Fig. 3
). The spinal canal was patent and there was secondary ectasia of the thecal sac due to loss of the posterior bony elements. The neural exit foramina were unimpeded. Serum biochemistry, including calcium, phosphate and parathyroid hormone levels, was within the normal limits.
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Only three cases of osteolysis of the cervical spine have been reported previously. All of these patients showed extensive osteolysis at other sites, including the digits, distal ulna and radius. All except one had associated mandibular resorption. Two of the patients had associated pyramidal tract signs and one patient developed a neuropathic arthritis due to nerve entrapment [9]. Spinal cord compression is less likely to occur in our patient in the face of almost complete osteolysis of the laminae and spinous processes.
CT or MRI features of osteolysis of the cervical spine and mandible have not been reported previously. Apart from showing marked bone resorption, both the CT and MRI images demonstrated rotation of the cervical vertebral bodies, for which there is no obvious explanation. We postulate that osteolysis at the sites of ligamentous insertion resulted in ligamentous instability, allowing uninhibited rotatory contraction of the paraspinal muscles and leading to rotatory scoliosis of the cervical spine.
The pathogenesis of osteolysis is poorly understood, although the condition is frequently associated with severe Raynaud's phenomenon and dcSSc [12]. The condition can occur at any time during the course of the disease, and in some instances, as in our patient, can accelerate many years after the onset of SSc. The current hypothesis is that bone resorption is the result of ischaemia, due to a combination of the microvasculopathy of SSc and pressure ischaemia secondary to skin tightening and muscular atrophy. No humoral factors have been reported, but it is noteworthy that acro-osteolysis has been reported in one study to be more common in patients who are positive for anti-topoisomerase-1 antibody [12]. Bone turnover has not been studied specifically in this subgroup of SSc patients, but there is evidence of increased bone turnover in SSc generally [13]. Bone collagen breakdown products were not measured in our case due to the unavailability of the service.
SSc, especially the dcSSc subset, can be associated with severe physical disability for a variety of reasons, including skin induration, joint contractures, inflammatory arthritis, myopathy and osseous resorption. In our patient the last feature has resulted in progressively worsening hand function and severe difficulty with mastication, but so far there have been no neurological sequelae. Antiresorptive therapy with alendronate has been initiated in an attempt to halt the resorptive process. Reconstructive surgery for the mandible, in an attempt to improve mastication, is being considered.
Notes
Correspondence to: M Tikly, Division of Rheumatology, Department of Medicine, Chris Hani Baragwanath Hospital, P.O. Bertsham 2013, South Africa.
References