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: Mutations detected in two of four of these are missense mutations , normally rare in A - T patients .
### Output Text:
Mutations detected in two of four of these are missense mutations , normally rare in <span class="disease">A - T</span> patients . 