Introduction Sometimes a clinical ‘hunch’ prompts urgent management in order to prevent life-threatening complications; illustrated by this case of herpes simplex viral (HSV) encephalitis which presented with an atypical rash, visual and tactile hallucinations.

Case History An 18-year-old man presented with a rash following unprotected sexual intercourse. On examination, he was pyrexial and had a florid erythematous, pustular rash on his face, trunk, arms and genitalia (see poster images).

Three days following admission he became disorientated, emotionally labile and developed hallucinations of small animals and a sensation of rain drops on his shoulders.

Investigations Vesicle swab PCR was positive for HSV 1. A CT scan of head was normal and CSF analysis demonstrated a normal opening pressure, 4 white cells, glucose 4.1mmol/L (serum glucose 6.4mmol/L) and an elevated protein, 0.6 g/L. CSF viral PCR for HSV 1 was positive.

Conclusions HSV encephalitis is associated with high morbidity and mortality, especially in untreated cases or when there is diagnostic delay. This rare case secondary to eczema herpeticum, coupled with the known poor clinical outcomes illustrates the need for a high level of clinical suspicion and the timely role of a diagnostic hunch.