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: This suggests that any greater amount of segregation distortion at the myotonic dystrophy locus must result from events following sperm ejaculation .
### Output Text:
This suggests that any greater amount of segregation distortion at the <span class="disease">myotonic dystrophy</span> locus must result from events following sperm ejaculation . 