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: Muscle expression of glucose - 6 - phosphate dehydrogenase deficiency in different variants .
### Output Text:
Muscle expression of <span class="disease">glucose - 6 - phosphate dehydrogenase deficiency</span> in different variants . 