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: The presence of the DTDST R279W mutation in a total of 11 patients with AO2 or DTD emphasizes the overlap between these conditions .
### Output Text:
The presence of the DTDST R279W mutation in a total of 11 patients with <span class="disease">AO2</span> or <span class="disease">DTD</span> emphasizes the overlap between these conditions . 