Following the discovery of the anti-AQP-4 antibody, Pittock et al. identified a thymic carcinoma in an NMO patient.28 A subsequent review by the Mayo Group found an association between NMO and a variety of other malignancies including breast, bronchus, thyroid, carcinoid and lymphoma.29 The Indian man in our series presented with NMO first and became aware of a testicular mass about 17 months later. This evidence concerns the gene AQP4 and neuromyelitis optica.