Daijiro Morohoshi （諸星大二郎）is definitely a weird precursor of Junji Ito but, unfortunately, very difficult to find in English (and even in Chinese). His most famous work is the Yokai Hunter (妖怪ハンター) series of the 1970s-80s.
A good overview of his stuff can be found here (Big5), along with a selection of “four favorites” (Big 5). Not altogether unrelated, some good horror manga recommendations from Silberstein here. Ito isn’t the only one who owes a debt to Morohoshi, legendary anime dude Miyazaki’s Princess Mononoke borrows heavily from the sylvan tribes of Mud Men.