What is the medical term meaning build-up of melanin?

A melanin buildup which is called post-inflammatory hyperpigmentation (PIH) will cause your skin to darken as in a tan. When it builds up too much you can get dark brown patches. It has many causes - sunburn, bruises, cuts, acne, fungal infections, eczema, psoriasis, etc. In most cases it will fade over time. Treatment with a lightening agent, such as Hydroquinone will speed up the process. It could take as long as 6 months ....................