In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Transplantation - associated microangiopathy ( TMA ) occurred in 7 patients ( 29 % ) , with 2 cases of acute renal failure .
### Output Text:
Transplantation - associated microangiopathy ( TMA ) occurred in 7 patients ( 29 % ) , with 2 cases of acute renal failure . 