MSFinals-1489

A dishevelled-looking 70-year-old woman is admitted from a nursing home following a fall. Her son indicates that she has become increasingly forgetful over the last 2 months. She has had diarrhoea for the last 3 weeks, thought to be related to an outbreak of norovirus at her nursing home, and has been vomiting occasionally. On examination you notice a scaly red rash on her neck and hands.
What is the most likely diagnosis?