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: Characterisation of the expression of this gene in patient tissues has thus far generated conflicting data on alterations in the steady state levels of DMPK mRNA , and on the final DMPK protein levels in the presence of the expansion .
### Output Text:
Characterisation of the expression of this gene in patient tissues has thus far generated conflicting data on alterations in the steady state levels of DMPK mRNA , and on the final DMPK protein levels in the presence of the expansion . 