Hypopigmented patches may be seen in:

Nevus anaemicus (NA) - Congenital disorder characterized by macules of varying size and shape that are paler than the surrounding skin and cannot be made red by trauma, cold, or heat. Paler area is due to the blood vessels within the area which are more sensitive to body's normal vasoconstricting chemicals. Hyperpigmentary disorders: Nevus of OTA Nevus of ITO Becker's Nevus