23 year old lean female with 7 yrs h/o PCOS with acne, mild hirsutism, irregular delayed periods presents with dark brown-black pigmentation over abrasions, pressure areas and minor superficial scars for last 6 yrs. Periods are regularized by combination pills, metformin 1g daily. Serum testosterone, DHEA, SHBG normal ( SHBG raised previously).

Opinion regarding cause and management of pigmentation welcome. Kindly suggest the management