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: Previous work from our laboratory demonstrated that a DNase l - hypersensitive site located adjacent to the repeats on the wild - type allele is eliminated by repeat expansion , indicating that large CTG - repeat arrays may be associated with a local chromatin environment that represses gene expression .
### Output Text:
Previous work from our laboratory demonstrated that a DNase l - hypersensitive site located adjacent to the repeats on the wild - type allele is eliminated by repeat expansion , indicating that large CTG - repeat arrays may be associated with a local chromatin environment that represses gene expression . 