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: In order to investigate the role of CAG expansion in the pathogenesis of HD , we have produced transgenic mice containing the full length human HD cDNA with 44 CAG repeats .
### Output Text:
In order to investigate the role of CAG expansion in the pathogenesis of <span class="disease">HD</span> , we have produced transgenic mice containing the full length human <span class="disease">HD</span> cDNA with 44 CAG repeats . 