Unilateral swollen optic disc: do not forget neurosyphilis.

A 51-year-old man presented with a 3 month history of progressive right visual loss. On examination, the only abnormal findings were a right visual acuity of 4/10 and a swollen right optic disc. The patient had previously undergone MRI that had been reported as being normal and a trial of corticosteroids under the care of the referring ophthalmologist. An extensive battery of blood tests was normal apart from a rapid plasmatic reagin titre of 1:64. ELISA revealed elevated levels of total and immunoglobulin M antibodies against Treponema pallidum. Cerebrospinal fluid analysis revealed a mild leucocytosis and mildly elevated protein content. The patient was treated with a 5 week course of penicillin. Three months after starting treatment, his right visual acuity had improved to 8/10 and his right optic disc swelling had resolved.