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: In 10 of these families , all the homozygotes have a 137 - bp insertion in their cDNA caused by a point mutation in a sequence resembling a splice - donor site .
### Output Text:
In 10 of these families , all the homozygotes have a 137 - bp insertion in their cDNA caused by a point mutation in a sequence resembling a splice - donor site . 