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A 38-year-old woman with Systemic Lupus Erythematosus (SLE) was admitted with sudden onset of painful proptosis of her left eye (figure 1A). Examination revealed a markedly proptosed left eye with chemosis, ptosis and painful reduction of eye movements. Visual acuity was preserved. Apart from coryzal symptoms, there were no other systemic features of infection. A CT scan of the orbits revealed diffuse thickening of the left lateral rectus muscle (Solid arrows) with retro-orbital fat stranding (Broken arrow), compatible with focal myositis (figure 1B,C). There was no other intracranial space occupying lesion. Her creatine kinase levels and thyroid function were normal, anti-neutrophil cytoplasmic antibody was negative but erythrocyte sedimentation rate (ESR) was markedly elevated (102 mm/h). Her initial SLE manifestations were myositis (creatine kinase (CK) 13 000 U/l (normal 20–300 U/l) with myopathic changes on electromyography), autoimmune haemolytic anaemia, cutaneous vasculitis and positive serologies (anti-nuclear antibody, anti-dsDNA, hypocomplementemia). Of note, she was treated for a flare of myositis (rising CK, ESR and anti-dsDNA) just 2 months prior with dose escalation of prednisolone and weekly methotrexate, having failed azathioprine, mycophenolate mofetil and cyclophosphamide in the past. This current episode was not accompanied by any apparent weakness in other muscle groups. She responded well to high dose intravenous steroids with complete resolution of proptosis.
Orbital myositis is a subtype of the Orbital Inflammatory Syndrome, largely an idiopathic inflammatory disease involving any of the orbital structures.1 It has been reported in many rheumatological conditions, including SLE. It is mostly unilateral and remains largely a diagnosis of exclusion. Important differentials which should be ruled out by initial investigations include infectious, endocrine (essentially, Grave's opthalmopathy), infiltrative (sarcoidosis) and neoplastic causes.2 Systemic SLE activity is not always noted at onset of the ocular manifestations hence a high index of suspicion should be maintained in predisposed patients. The pathological basis in autoimmune disease related orbital myositis is not fully elucidated, but most evidence implicates an immune-mediated process. Histological specimens are rather non-specific with benign lymphoid hyperplasia and a fibrovascular tissue reaction. Some have revealed granulomatous deposits, distinct from those seen in the granulomatous diseases like sarcoidosis. Complement deposits as well as human leukocyte antigen (HLA) class-I antigens have been demonstrated within the involved muscle tissues.3 ,4 The widely reported apparent dissociation between SLE activity and onset of orbital myositis has cast doubt into a true disease association.2 Diagnosis relies on good history and clinical examination, exclusion of differentials, as well as careful interpretation of CT or MRI findings within the context of the individual case. Patients respond well to corticosteroids but biopsy should not be delayed in patients who do not show response to guide further treatment.1 ,5 Recurrences have been documented despite good initial response to corticosteroids and there is a trend towards the use of disease modifying agents.4
Contributors Both authors contributed to the preparation of the manuscript. AS: article writing and image formatting. SV: article writing and supervision.
Competing interests None.
Patient consent Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
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