A 70-year-old male patient presented with hyper pigmented (blackish discolouration) hyper trophick plaques on bilateral feet, knees, hands and back since last 6 months; with severe unbearable burnining sensation, more in feet. H/O Diabetes 10 years, blood sugars under controlled, vitals signs normal. Patient's occupation: preparation of ayurvedic medications since 30-40 years.

What should be the diagnosis of skin disease? Suggest the line of treatment?