Is Skin Problem With Black Patches On Body Curable?

Doctor, my name is suresh from India 7 Im working in qatar. I have a skin problem from 5 years. The problem is the, In my skin, some small patches are occuring in black/blueish colours. The whole body is becomming like that. Even in my palm the colour patches are occured. please help me doctor. I want to know the name of this skin disease and whether it is curable or not?