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: Localized scleroderma has no recognized internal organ involvement but may be disfiguring and disabling when the cutaneous lesions are extensive or affect children .
### Output Text:
Localized scleroderma has no recognized internal organ involvement but may be disfiguring and disabling when the cutaneous lesions are extensive or affect children . 