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 found that a group of patients have mild skeletal changes which may be secondary consequences of myotonia , while another group of patients appear to have primary bone dysplasia with myotonia .
### Output Text:
We found that a group of patients have mild skeletal changes which may be secondary consequences of <span class="disease">myotonia</span> , while another group of patients appear to have primary <span class="disease">bone dysplasia</span> with <span class="disease">myotonia</span> . 