This is an unusual streaky rash seen on the back and
abdomen. It arose following a meal of Shitake mushrooms. This is a distinctive
rash described as a flagellate dermatitis. It follows the ingestion of raw or
undercooked shitake mushrooms. These are popular mushrooms in Asian cooking but
a rash may only occur in around 2% of people consuming them raw or undercooked.
Sometimes the lesions do not blanch because lentinan, a thermolabile
polysaccharide releases interleukin 1 which causes vasodilatation and haemorrhage.
Linear petechiae can be seen elsewhere on the hands and feet. Localised
swelling and fever can also occur. The rash will resolve spontaneously over a
couple of weeks but some oral steroids early in the rash will help it resolve
more quickly. It is the distinctive streaky nature of the rash that suggests
the diagnosis. Bleomycin may cause a similar flagellate eruption but it
resolves with hyperpigmentation.
