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: OBSERVATIONS : A keratome skin specimen from 1 patient with sirolimus - induced capillary leak syndrome had a 2 . 3 - fold increase in percentage of apoptotic cells ( to 48 % ) compared with an unaffected sirolimus - treated patient with psoriasis ( 21 % ) .
### Output Text:
OBSERVATIONS : A keratome skin specimen from 1 patient with <span class="chemical">sirolimus</span> - induced capillary leak syndrome had a 2 . 3 - fold increase in percentage of apoptotic cells ( to 48 % ) compared with an unaffected <span class="chemical">sirolimus</span> - treated patient with psoriasis ( 21 % ) . 