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: Furthermore , we demonstrate that the Atm protein exists as two discrete molecular species , and that loss of one or of both of these can lead to the development of the disease . .
### Output Text:
Furthermore , we demonstrate that the Atm protein exists as two discrete molecular species , and that loss of one or of both of these can lead to the development of the disease . . 