Woman with lower back pain, SIADH and a twist of Lyme.

A 62-year-old woman was admitted with a 3-week history of atraumatic bilateral lower back pain, progressive ascending flaccid paralysis, hyponatraemia and constipation. She was otherwise in good health with only a recent diagnosis of acute gastroenteritis that preceded her presenting symptoms. Her initial laboratory evaluation was consistent with Syndrome of Inappropriate Antidiuretic Hormone (SIADH) but was otherwise unremarkable. MRI of the spine revealed bilateral diffuse nerve root enhancement from at least C6 to the conus level, suggesting an inflammatory process. Lumbar puncture demonstrated high protein (629 mg/dL) with marked pleocytosis (363 cells/mcL) incompatible with albuminocytological dissociation typically seen in Guillain-Barre syndrome. A thorough diagnostic evaluation was undertaken to explore potential infectious, malignant and autoimmune conditions. Lyme disease serology (ELISA and Western Blot, IgM and IgG) was positive leading to a final diagnosis of lymphocytic meningoradiculitis or Bannwarth syndrome. © BMJ Publishing Group Limited 2018. No commercial re-use. See rights and permissions. Published by BMJ.