In the sentence extracted from biomedical literature, identify all the disease entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="disease"> to denote a disease.

### Input Text: The ataxia - telangiectasia gene product , a constitutively expressed nuclear protein that is not up - regulated following genome damage .
### Output Text:
The <span class="disease">ataxia - telangiectasia</span> gene product , a constitutively expressed nuclear protein that is not up - regulated following genome damage . 