Posterior scleritis mimicking orbital cellulitis

In 2008, an 88-year-old woman with a background of well controlled systemic hypertension and high myopia presented to an emergency department with a 5-day history of left periorbital swelling, erythema and mild discomfort, without visual loss. She was seen in the ophthalmology clinic on the same day. Her visual acuity was 6/12 in each eye. She was afebrile, with left upper and lower lid erythema, oedema closing the palpebral fissure, and conjunctival and scleral injection. Slit-lamp biomicroscopy revealed normal anterior chambers; clear, well centred intraocular lens implants from previous uncomplicated cataract surgery; and posterior staphylomata (an incidental finding of bulging of the globe seen in some highly myopic patients). A computed tomography (CT) scan revealed left periorbital soft tissue thickening, with stranding confined to the preseptal area (Figure A). Radiologically, the patient appeared to have periorbital cellulitis, although clinical examination, being more sensitive to ocular signs, revealed postorbital septal spread of infection as evidenced by scleral injection (not expected to be seen on a CT scan), leading to the diagnosis of orbital cellulitis. Intravenous antibiotics were administered for 3 days, with moderate resolution of the periorbital swelling, although the scleral injection remained.

Three days after discharge on oral antibiotics, the patient re-presented to the emergency department with recurrence of left periorbital swelling, erythema and discomfort. After administration of intravenous antibiotics for five days, her lid oedema and erythema resolved, but conjunctival and scleral injection persisted. Investigations during this second admission revealed raised erythrocyte sedimentation rate (ESR) and C reactive protein (CRP) level, with a normal blood leucocyte count.

Soon after her second discharge, the patient presented again with persisting and worsening erythema of the left eye, with no associated lid swelling or erythema. A clinical diagnosis of non-necrotising anterior scleritis was made (Figure B), and it was thought that conjunctival lymphoma should be excluded. B-scan ultrasonography revealed fluid in Tenon’s capsule and scleral thickening, consistent with anterior and posterior scleritis (Figure B), and investigations again revealed a raised ESR and CRP level. Screening for tuberculosis (TB) (Mantoux test and chest x-ray), antinuclear antibodies, extractable nuclear antigen antibodies, rheumatoid factor, syphilis, and angiotensin-converting enzyme (an indicator of sarcoidosis) were negative. Screening for Wegener’s granulomatosis with perinuclear antineutrophil cytoplasmic antibodies was positive, but attempted confirmation by screening for antiproteinase 3 antibodies and antimyeloperoxidase antibodies was negative. Magnetic resonance imaging revealed marked high T2 signalling and enhancement of the left sclera, extraocular muscle insertions and distal optic nerve (Figure C). A scleroconjunctival biopsy was performed to exclude conjunctival lymphoma or other uncommon diagnoses, such as tuberculosis and fungal infection. The biopsy revealed a dense inflammatory infiltrate consisting of B and T lymphocytes, plasma cells and occasional neutrophils, with no granulomatous inflammation. Flow cytometry; immunohistochemistry; bacterial, fungal and mycobacterial staining and culture; and TB polymerase chain reaction tests were all negative. Haematological consultation excluded systemic or central nervous system lymphoma.

A short course of oral prednisolone (1 mg/kg/day for 14 days) resulted in complete resolution of the patient’s signs and symptoms, and she remained well at 6-week follow-up.

A: Sagittal computed tomography scan showing left periorbital soft tissue thickening and posterior staphyloma.

B: Superior scleral injection and B-scan ultrasound showing fluid in Tenon’s capsule and scleral thickening, consistent with anterior and posterior scleritis.

C: Magnetic resonance images showing high T2 signalling and enhancement of the left sclera, extraocular muscle insertions, and distal optic nerve.