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: A mutation in autosomal dominant myotonia congenita affects pore properties of the muscle chloride channel .
### Output Text:
A mutation in <span class="disease">autosomal dominant myotonia congenita</span> affects pore properties of the muscle chloride channel . 