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: The episode was characterized by a vasculitic skin rash associated with large joint arthritis , pyrexia and parotiditis but no renal or pulmonary involvement .
### Output Text:
The episode was characterized by a vasculitic skin rash associated with large joint arthritis , pyrexia and parotiditis but no renal or pulmonary involvement . 