Background: A broad differential diagnosis has to be considered in a patient with swollen discs. Myeloproliferative disorders such as leukemia and lymphoma can in rare cases cause infiltrative optic neuropathy.
History and signs: Two patients initially presented with slowly progressive severe visual loss. History was unremarkable except for previously noted slightly elevated white blood cell count for which - according to their general physicians - no treatment or work-up was required. At presentation, bilateral disc swelling was present. Magnetic resonance imaging showed enhancement of the entire optic nerves sparing the chiasm. No other intracranial lesion was found. Cerebrospinal fluid contained no malignant cells.
Therapy and outcome: After bone marrow aspiration the diagnosis of non-Hodgkin's lymphoma and granulocytic leukemia, respectively, was made. Treatment resulted in visual recovery.
Conclusion: Work-up in a patient with swollen discs should always include white blood cell count. If the result is abnormal further exploration should be pursued. Elevated white blood cell count may be the only hint of optic nerve infiltration caused by a myeloproliferative disorder and its treatment can result in remarkable recovery.