A woman in her forties with unilateral blurred vision and pain upon eye movement.

BACKGROUND

Toxoplasmosis is a relatively common cause of infectious papillitis and neuroretinitis, which may affect both immunocompetent and immunodeficient patients.

CASE PRESENTATION: A previously healthy woman in her mid-forties presented with subacute onset of unilateral blurred vision and retrobulbar pain exacerbated by eye movements. Ophthalmological assessment revealed decimal best-corrected visual acuity of 0.75, an ipsilateral swollen disc and a peripapillary infiltrate. Serology indicated acute infection with Toxoplasma gondii. Cerebral MRI showed a periventricular lesion, and oligoclonal bands were detected in the cerebrospinal fluid.

INTERPRETATION: This case illustrates that even when symptoms, MRI and cerebrospinal fluid findings suggest demyelinating disease, differential diagnoses must be considered in order to mitigate the negative therapeutic and prognostic consequences of a misdiagnosis.