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: In conclusion , we demonstrated that a point mutation in a lariat branchpoint consensus sequence causes a null allele in a patient with FED .
### Output Text:
In conclusion , we demonstrated that a point mutation in a lariat branchpoint consensus sequence causes a null allele in a patient with <span class="disease">FED</span> . 