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: Two of the patients had only the I66M mutant mRNA , and one only the G27OD mutant mRNA .
### Output Text:
Two of the patients had only the I66M mutant mRNA , and one only the G27OD mutant mRNA . 