Found this thanks to Ars. (Yeah that’s three “i”s in a row.)
The case report reads very tongue-in-cheek, containing a description of the Wii controller that can only be described as clinical, and noting that, unlike in real tennis, the resident’s level of fitness did not preclude his ability to overdo it: “Unlike in the real sport, physical strength and endurance are not limiting factors.”
Apparently, Acute Wiiitis is actually a variant of a disease that was first described in 1990, Nintendinitis, but the presentation is distinct enough to warrant a specific term. Those curious about these sorts of ailments may also want to check out the description of Nintendo elbow and Ulcerative Nintendinitis.