A 27 year old female came with the complaints of itching, blackish discoloration with scaly lesions affecting only digits of both upper and lower limbs since 2 years.They started as small reddish macular lesions and slowly progressing. She is a housewife. She is neither a diabetic nor  a hypertensive.

No history of atopy. No significant family history. What could be the etiology and treatment of this disease?