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: Usually it is a self - limited disorder , but corticosteroid therapy may be needed in life - threatening cases since early treatment with corticosteroids in severe cases can prevent complications .
### Output Text:
Usually it is a self - limited disorder , but <span class="chemical">corticosteroid</span> therapy may be needed in life - threatening cases since early treatment with <span class="chemical">corticosteroids</span> in severe cases can prevent complications . 