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: Kniest dysplasia is a severe chondrodysplasia caused by the defective formation of type II collagen .
### Output Text:
<span class="disease">Kniest dysplasia</span> is a severe <span class="disease">chondrodysplasia</span> caused by the <span class="disease">defective formation of type II collagen</span> . 