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: Furthermore , the cation - to - anion permeability ratio of the mutant is much greater than that of the wild - type channel .
### Output Text:
Furthermore , the cation - to - anion permeability ratio of the mutant is much greater than that of the wild - type channel . 