Two sides of the same coin

<h3></h3> A 56-year-old woman with a background of recently-diagnosed neuromyelitis optica spectrum disorder associated with aquaporin-4 antibodies (AQ4-NMOSD), presented with a two-month history of progressive decline in mobility. She had lost twelve kilograms in weight, without loss of appetite, and described difficulty in swallowing and new hoarseness of voice. She had an additional previous medical history of thyrotoxicosis, now stable on thyroxine, and was a lifelong smoker. Her initial presentation with NMOSD one year previously had been with retrobulbar optic neuritis, with no spinal cord involvement. At the time of this presentation, she had been taking azathioprine for a year and had stopped prednisolone. On examination, tandem walking was impaired. Reflexes were reduced in the lower limbs, but power was normal. Neurophysiological testing revealed typical findings for Lambert- Eaton myasthenic syndrome (LEMS), with reduced compound muscle action potentials (CMAPs) and incrementation post-stimulation. Voltage-gated calcium channel antibodies were strongly positive. She had good symptomatic response to 3,4-diaminopyridine. Serial PET imaging has revealed no evidence of underlying malignancy, and she is currently treated with rituximab and has returned to work. Her NMOSD has remained in remission. This case highlights the need to consider additional, treatable, autoimmune disorders in the context of deterioration in NMOSD.