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: Molecular bases of C7 deficiency : three different defects .
### Output Text:
Molecular bases of <span class="disease">C7 deficiency</span> : three different defects . 