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: Adult Dmpk - / - mice show ultrastructural changes in muscle and a 50 % decrease in force generation compared to young mice .
### Output Text:
Adult Dmpk - / - mice show ultrastructural changes in muscle and a 50 % decrease in force generation compared to young mice . 