Really a pretty easy question since denial of leave could be itself an adverse employment action. Nevertheless, it gets missed as the shown by the Fourth Circuit's reversal of a summary judgment recently in Jacobs v North Carolina Administrative Office of Courts:
We note that, in addition to serving as evidence of hostility, the denial of leave can itself be an adverse employment action compensable under the ADA’s retaliation provision. Wells v. Gates, 336 F. App’x 378, 383–384 (4th Cir. 2009) (per curiam).
Jacobs is an excellent opinion examining numerous issues pertinent to ADA and disability discrimination cases.
Robert L. Abell
www.RobertAbellLaw.com