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: Each of the three patients was found to be heterozygous for a c862t transition predicting a R279W substitution in the third extracellular loop of DTDST .
### Output Text:
Each of the three patients was found to be heterozygous for a c862t transition predicting a R279W substitution in the third extracellular loop of DTDST . 