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 skin lesion resembled elastosis perforans serpiginosa , which has been reported as a rare side effect in patients with Wilson ' s disease but not in patients with rheumatoid arthritis treated with penicillamine .
### Output Text:
The skin lesion resembled elastosis perforans serpiginosa , which has been reported as a rare side effect in patients with Wilson ' s disease but not in patients with rheumatoid arthritis treated with <span class="chemical">penicillamine</span> . 