In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: A literature review revealed no prior reports of pericarditis in anti - MPO pANCA - positive vasculitis associated with propylthio - uracil therapy .
### Output Text:
A literature review revealed no prior reports of pericarditis in anti - MPO pANCA - positive vasculitis associated with <span class="chemical">propylthio - uracil</span> therapy . 