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 also suggest that C9 deficiency may be more common among Caucasians than has been reported . .
### Output Text:
We also suggest that <span class="disease">C9 deficiency</span> may be more common among Caucasians than has been reported . . 