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: Within the kidney , VHL mRNA was differentially expressed within renal tubules suggesting that the VHL gene product may have a specific role in kidney development .
### Output Text:
Within the kidney , <span class="disease">VHL</span> mRNA was differentially expressed within renal tubules suggesting that the <span class="disease">VHL</span> gene product may have a specific role in kidney development . 