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: The C7 defect is more enigmatic the protein is of normal molecular weight , low circulating concentration , and altered isoelectric point .
### Output Text:
The C7 defect is more enigmatic the protein is of normal molecular weight , low circulating concentration , and altered isoelectric point . 