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: Absence of disease phenotype and intergenerational stability of the CAG repeat in transgenic mice expressing the human Huntington disease transcript .
### Output Text:
Absence of disease phenotype and intergenerational stability of the CAG repeat in transgenic mice expressing the human <span class="disease">Huntington disease</span> transcript . 