Hypo pigmentation can occur as a result of autoimmune disease like Vitiligo or as a consequence of post-inflammatory reaction following a skin injury as result of sun exposure or treatments associated thermal or chemical burn.
Micro needling therapy is well recognized as treatment of excessive pigment deposition, but it also can be effective for cases with the pigment loss due to a post-inflammatory reaction. Depth of needles is quite important in this instances, derma-stamp is more preferable as depth of penetration into skin is more predictable. Furthermore,perpendicular to the skin surface insertion of needles is also less painful, as a rotating motion of a derma-roller can cause micro-tears of skin and that can be more painful.
Micro-needling is unlikely to be effective in cases of Vitiligo.