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: We identified three missense mutations ( I66M , G270D , L618S ) and one exon - 6 skipping ( 535 - 573del ) .
### Output Text:
We identified three missense mutations ( I66M , G270D , L618S ) and one exon - 6 skipping ( 535 - 573del ) . 