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: Muscles from mature mice show variation in fibre size , increased fibre degeneration and fibrosis .
### Output Text:
Muscles from mature mice show variation in fibre size , increased <span class="disease">fibre degeneration</span> and <span class="disease">fibrosis</span> . 