hypopigmentation 
noun [mass noun]
Inadequate pigmentation of the skin.The other major side effect of cryosurgery for this lesion is hypopigmentation....
- Side effects are few, but may include tendon rupture, infection, steroid flare, hypopigmentation, and soft tissue atrophy.
- Once the lesions have resolved, there may be transient hyper- or hypopigmentation.