Hyponatraemia associated with the use of selective serotonin re-uptake inhibitors

A man with a 15-year history of non-Hodgkin's lymphoma presented with disseminated herpes zoster which initially responded to aciclovir. This was shortly followed by an acute exacerbation in the sites previously affected which was apparently resistant to antiviral therapy. Biopsy revealed a dense monomorphic lymphocytic infiltrate below active herpes zoster which had the same morphology and immunoreactivity as the underlying lymphoma. His clinical condition resolved with further chemotherapy for his lymphoma and continued treatment with aciclovir.