Crohn's colitis (CD affecting the colon) is actually treated the very same way (with meds and such) as UC is treated...there are 5 subtypes of crohn's (5 different main areas that CD is most common) {see this link}
http://www.ehealthmd.com/library/crohnsdisease/CD_types.html
And although CD can affect any part of the GI tract from mouth to anus and UC is limited to the colon/rectom, the very same extraintestinal manifestations can occur in either CD or UC, especially skin issues (skin issues are more common for those with crohn's colitis (when the colon is involved) and therefore makes skin issues a more constant for UCers.
CD is patchy (or skipped) patterns of inflammation (a good GI can detect the difference) with healthy tissues in between inflamed tissue...UC will have the entire area inflamed with no skipped/patchy areas.
Patients are often misDX, this never happend to me as I also have the perianal crohn's skin tags which are a dead give-away of crohn's...I have crohn's colitis, and when I first got sick it was affecting my anus with the tags, my rectom (proctitis) my colon, and my TI so crohn's can also affect more than one area at a time, and although my CD has remained constant the entire 19 yrs I've had it, in the colon and anus, it has stayed clear of the TI and comes and goes in the rectom. Therefore I definitely still have crohn's and it has not "changed" into UC, as my pattern of inflammation is that of CD and not UC, plus the perianal crohn's skin tags.