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: Skin rashes , proteinuria , systemic lupus erythematosus , polymyositis and myasthenia gravis have all been recorded as complications of penicillamine therapy in patients with rheumatoid arthritis .
### Output Text:
Skin rashes , proteinuria , systemic lupus erythematosus , polymyositis and myasthenia gravis have all been recorded as complications of <span class="chemical">penicillamine</span> therapy in patients with rheumatoid arthritis . 