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: A substitution at codon 86 resulted in an extremely variable expression of the disease in a large Swiss family .
### Output Text:
A substitution at codon 86 resulted in an extremely variable expression of the disease in a large Swiss family . 