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: A case of phenytoin ( DPH ) encephalopathy with increasing seizures and EEG and mental changes is described .
### Output Text:
A case of <span class="chemical">phenytoin</span> ( <span class="chemical">DPH</span> ) encephalopathy with increasing seizures and EEG and mental changes is described . 