What could cause an odd rash that extends from the stomach to legs?

Oops need to see: Could be almost anything. Depends on the kind of rash (bumpy, red, tiny, irregular, weeping, itchy, etc). This time of year pityriasis rosacea (pr) is common & may start with a spot (herald patch) on the lower abdomen (or back, extremities) then radiate to other parts of the body. See your doctor for a firm diagnosis. Picture is pr.