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 G6PD deficiency has been investigated in Mediterranean , Seattle - like and A - variants .
### Output Text:
Muscle expression of <span class="disease">G6PD deficiency</span> has been investigated in Mediterranean , Seattle - like and A - variants . 