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: Our results show that huntingtin is cleaved by cysteine proteases and suggest that HD might be a disorder of inappropriate apoptosis . .
### Output Text:
Our results show that huntingtin is cleaved by cysteine proteases and suggest that <span class="disease">HD</span> might be a <span class="disease">disorder of inappropriate apoptosis</span> . . 