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: Very - long - chain acyl - CoA dehydrogenase ( VLCAD ) is one of four straight - chain acyl - CoA dehydrogenase ( ACD ) enzymes , which are all nuclear encoded mitochondrial flavoproteins catalyzing the initial step in fatty acid beta - oxidation .
### Output Text:
Very - long - chain acyl - CoA dehydrogenase ( VLCAD ) is one of four straight - chain acyl - CoA dehydrogenase ( ACD ) enzymes , which are all nuclear encoded mitochondrial flavoproteins catalyzing the initial step in fatty acid beta - oxidation . 