Pigmentation loss as a result of skin damage:

If you’ve had a skin infection, blisters, burns or other trauma to your skin, you may have a loss of pigmentation in the affected area. The good news with this type of pigment loss is that it’s frequently not permanent, and cosmetics can be used to cover the area.

A more serious problem of Hypopigmentation is known as Vitiligo.

Vitiligo:

Vitiligo is pigment loss due to the body’s immune system attacking pigment cells (melanocytes). Other associated immune system diseases include diabetes, pernicious anemia, thyroid disease, or Addison’s disease. Vitiligo causes smooth, white skin patches, usually around the mouth and eyes, or on the back of the hands. In some people, these patches can appear all over the body. There is no cure for vitiligo, but there are several treatments, including dyes or psoralens (light-sensitive drugs) used in combination with ultraviolet a light treatment, and more recently the excimer laser, which delivers UVB light.

For treatment for Vitiligo Caci recommend you visit a dermatologist.