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 patient was shown to be heterozygous for DNA markers in the C6 , C7 and C9 region of chromosome 5 and therefore appears to be a compound heterozygote for two uncharacterized C9 deficiency genes .
### Output Text:
The patient was shown to be heterozygous for DNA markers in the C6 , C7 and C9 region of chromosome 5 and therefore appears to be a compound heterozygote for two uncharacterized <span class="disease">C9 deficiency</span> genes . 