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: These defects are associated with a characteristic set of polymorphic DNA markers in the C6 / C7 region , forming a distinct haplotype .
### Output Text:
These defects are associated with a characteristic set of polymorphic DNA markers in the C6 / C7 region , forming a distinct haplotype . 