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Eosinophilic myositis is a rare inflammatory condition of skeletal muscle associated with peripheral eosinophilia.1 Orbital eosinophilic angiocentric fibrosis2 and idiopathic orbital myositis3 have been reported. We report the first case of cyclical orbital eosinophilic myositis (OEM).
A 38‐year‐old woman presented to the ocular motility service in January 2006 with a one‐week history of left‐sided ptosis and diplopia. In the past four years, she had reported alternating ptosis and retro‐ocular pain that recurred at six‐week intervals. She was systemically well. Cranial computed tomography, magnetic resonance imaging, tensilon testing, neurophysiology and anti‐acetylcholine receptor antibody had been normal.
Ocular examination revealed left partial ptosis, left hypotropia (20 prism dioptres (PD)) ipsilateral limitation of elevation, and ipsilateral temporal conjunctival hyperaemia (fig 1A, BB).). Visual acuity was normal bilaterally. Full blood count, inflammatory markers, serum angiotensin‐converting enzyme, autoimmune screen, thyroid antibody, Lyme and worm serology were normal. Chest X‐ray, thorax and abdominal computed tomography did not demonstrate regional lymphadenopathy or metastases. Magnetic resonance imaging scan showed increased signal in all rectus muscles (fig 1C1C).). Presumed bilateral orbital myositis was managed with intravenous methylprednisolone 1 g a day for two days. The hypotropia and ptosis improved rapidly (2‐PD esophoria). She developed two recurrences over a 10‐week period, one affecting the right side (fig 2A2A).). Incisional biopsy of the left lateral rectus muscle demonstrated extensive disruption of the skeletal muscle by lymphoid aggregates with abundant eosinophils (fig 2B2B).). This was reviewed by the national centre for tropical medicine and the regional reference laboratory. There were no histological features to suggest parasitic infection, and a diagnosis of OEM was made. Maintenance steroid therapy was started; however, the condition has remained unresponsive (fig 2C2C).). Topical cyclosporin A has been tried without effect, and the patient, who remains disabled by these episodes, has declined any further intervention.
Cyclical OEM is previously unreported. It is a benign inflammation with a cyclical frequency and chronic course. Important clinical features include alternating ptosis, large‐angle vertical ocular deviations up to 50PD, and episcleral inflammation. A review by the regional clinical immunology unit confirmed a non‐infectious, immune‐mediated OEM. The pathogenesis of OEM may represent an abnormal activation of ocular allergic inflammatory mechanisms.4 Allergy‐inducing T‐helper type 2 cytokines such as IL‐5 and eotaxin promote the activation and degranulation of eosinophils5 within ocular skeletal muscle. Focal necrosis of extra‐ocular skeletal muscle fibres leads to a self‐limiting ocular myopathy. Eosinophils may persist in tissue, and recurrent reactivation may account for the cyclical frequency in our patient. Muscle is recognised to be resistant to apoptosis, and in inflammatory myopathies muscle fibres do not die.6 In our patient, a complete recovery of extra‐ocular muscle function occurred between attacks. Our biopsy did not reveal any signs of myofibrosis. High‐dose intravenous steroids appeared to be effective early on; however, OEM becomes steroid‐resistant over time. Newer immunomodulatory therapy may play a role in reducing the duration of episodes and delay recurrence.7 Cyclical OEM is an unusual condition that is diagnosed by exclusion and early ocular muscle biopsy is advisable.
The authors would like to thank Professor P L Chiodini, Department of Parasitology, London School of Tropical Medicine and Hygiene, for his opinion in the case and review of the pathology sample.