hyperpigmentation 
noun [mass noun]
Excessive pigmentation of the skin.The typical signs of chronic venous insufficiency include pedal edema, varicose veins and skin hyperpigmentation....
- The most common complication of laser resurfacing is hyperpigmentation - skin tone that turns darker than normal.
- Some patients never develop the full classical triad of hyperpigmentation, hypotension, and hyponatraemia.
- rider stone
- Ride, Sally
- ride-share
- ride-sharing
- ride shotgun
- ride skimmington
- ride someone down
- ride something out
- ride the clutch
- ride the pine (or bench)
- ride the rods (or rails)
- ride to hounds
- ride up
- rideway
- ridge
- ridgeback
- ridge-band
- ridge barrow
- ridge bone
- ridge chain
- ridge crest
- ridge cucumber
- ridge-drill
- ridge form
- ridgel