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: We conclude that the mutations causing galactosemia are highly heterogeneous and that K285N is a second common galactosemia mutation in our population . .
### Output Text:
We conclude that the mutations causing <span class="disease">galactosemia</span> are highly heterogeneous and that K285N is a second common <span class="disease">galactosemia</span> mutation in our population . . 