Localised herpes zoster infection and SIADH.

Localised herpes zoster infection ('shingles') in older patients is a common presentation to primary, and sometimes secondary, care physicians. However, symptoms of hyponatraemia, caused by the rare complication of 'syndrome of inappropriate antidiuretic hormone secretion' (SIADH), may be mistaken for constitutional symptoms of the infection itself. Such patients may require closer monitoring or hospitalisation.