Help! Need to know if there's any link between leukemia and idiopathic guttate hypomelanosis?

No. Igh is a benign skin condition probably related to chronic sun exposure. Since it produces light discoloration of the skin, it is also considered a benign type of leukoderma (leukos [greek] = white, derma = skin). With the exception of the lexical connection, there is no relationship with leukemia, a form of blood cancer.