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: Atm , the mouse homolog of the human ATM gene defective in ataxia - telangiectasia ( A - T ) , has been identified .
### Output Text:
Atm , the mouse homolog of the human ATM gene defective in <span class="disease">ataxia - telangiectasia</span> ( <span class="disease">A - T</span> ) , has been identified . 