Erythrasma is a skin condition characterised by asymptomatic initially pink patches that become brown as the skin sheds.
Erythrasma is caused by corynebacterium, a gram positive bacteria.
If a woods lamp is held near a patch of erythrasma the erythrasma glows coral red due to porphyrins released by the bacteria.
It is commonest amongst diabetics and the obese.
Treatment is with topical fusidic acid/clindamycin or oral erythromycin if extensive.