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: As a cause of C9 deficiency , we found two different point mutations , both generating TGA stop codons in the coding sequence .
### Output Text:
As a cause of <span class="disease">C9 deficiency</span> , we found two different point mutations , both generating TGA stop codons in the coding sequence . 