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 G230E mutation causes substantial changes in anion and cation selectivity as well as a fundamental change in rectification of the current - voltage relationship .
### Output Text:
The G230E mutation causes substantial changes in anion and cation selectivity as well as a fundamental change in rectification of the current - voltage relationship . 