Background Optic neuropathies can not always easily be classified as neuritis or ischemic disease. Case report A 39 year old woman suffered from unilateral optic neuropathy 9 days after the acute onset of a general disease with erythema and joint swellings. The optic disc swelling and visual fields resembled an anterior ischemic optic neuropathy, however, a marked improvement was achieved by steroid treatment. The general disease proved to be erythema infectiosum. Conclusions Erythema infectiosum as a frequent children's disease causes very rarely central nervous involvement, optic neuropathy has not been reported yet. In cases of atypical optic neuropathies search for an underlying systemic disease is of value.