A 40 years old man, having very stout, stiff muscles paining always, (no cause found), developed these black spots, since one year. Can these be considered signs of developing diabetes mellitus . The reports of blood sugar test found to be considerably higher i.e. 200-250 mg.

Most probably the chronic stress of muscles pain has caused diabetes mellitus and by reducing body wt by 18 kg, sugar came to normal. What would be the probable cause of black spots?