Sir,

Idiopathic orbital inflammatory syndrome (IOIS) is a heterogeneous group of disorders characterized by orbital inflammation without any identifiable cause.1, 2 It commonly affects the EOMs, particularly the lateral rectus,3 lacrimal gland,4 and cavernous sinus.5 Classically it presents with unilateral pain, swelling, proptosis, diplopia, and reduced vision. We report the first case of bilateral IOIS involving all EOMs with an unusually grossly elevated creatinine kinase (CK) level and with a favourable response to steroids.

Case report

A previously healthy 7-year-old girl presented with 10 days of binocular vertical diplopia and bilateral eyelid swelling. Visual acuity (VA) was 6/6 in both eyes. She had a left ptosis, exotropia, and hypertropia. EOM demonstrated the limitation of elevation, adduction, and abduction (Figure 1a). Anterior and posterior segments of both eyes were normal and she was diagnosed with double elevator palsy. A week later, both ptosis and hypertropia had switched to the right. EOM limitation persisted. A week later, she had bilateral periorbital oedema and left proptosis. VA was 6/6 OD and 6/12 OS with a left RAPD. ESR was 69 mm/h, CRP 27 mg/l, and CK 4300 IU/l. There was no hepatosplenomegaly or rash. Muscle strength was MRC grade 5. CT scan showed the enlargement of all EOMs bilaterally (Figure 1b) and MRI confirmed EOM swelling from the muscle origin to insertion (Figure 1c). Acetyl-choline receptor antibodies, anti-mitochondrial antibodies, ANA, dsDNA antibodies, pANCA and cANCA cardiolipin antibodies, TFTs, thyroid antibodies, Rh factor, and ACE were all negative. She was diagnosed with bilateral IOIS and treated with intravenous and then oral steroids with complete clinical recovery. The patient remains well 2 years on.

Figure 1
figure 1

(a) Nine positions of gaze demonstrating the limitation of EOM. (b) CT scan demonstrating enlarged EOM. (c) MRI scan demonstrating enlarged EOM.

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Comment

To the best of our knowledge, this is the first report of bilateral IOIS in a child with grossly elevated levels of CK. Thus, IOIS should not be excluded on the basis of laterality and age. CK levels should be considered, alongside a high index of suspicion with a low threshold for MRI in order to prevent irreversible visual loss from optic nerve compression.