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: Difficulties in the ascertainment of C9 deficiency : lessons to be drawn from a compound heterozygote C9 - deficient subject .
### Output Text:
Difficulties in the ascertainment of <span class="disease">C9 deficiency</span> : lessons to be drawn from a compound heterozygote <span class="disease">C9 - deficient</span> subject . 