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: Nullizygous ( - / - ) mice showed only inconsistent and minor size changes in head and neck muscle fibres at older age , animals with the highest DMPK transgene expression showed hypertrophic cardiomyopathy and enhanced neonatal mortality .
### Output Text:
Nullizygous ( - / - ) mice showed only inconsistent and minor size changes in head and neck muscle fibres at older age , animals with the highest DMPK transgene expression showed <span class="disease">hypertrophic cardiomyopathy</span> and enhanced neonatal mortality . 