Skin melanin deposits on the back may be skin amyloidosis, post-inflammatory hyperpigmentation, and melioidosis. 1. Cutaneous amyloidosis: mainly amyloid protein abnormally deposited in tissues and organs, can also be deposited on the surface of the skin, the cause of cutaneous amyloidosis is still unclear. The cause of skin amyloidosis is still unclear. Mottled amyloidosis can be manifested as brown pigmented spots, which can be accompanied by itching and other symptoms. 2. Post-inflammatory hyperpigmentation: usually due to dermatitis or folliculitis in the back area, after which the inflammation is not sufficiently dissipated to form hyperpigmentation, which can disappear on its own under normal circumstances. 3. Melanosis: it is a diffuse hyperpigmentation skin disease mainly manifested in the face and neck, of course, it may also involve the back, resulting in hyperpigmentation of the back, the etiology and pathogenesis are still unclear, and most of the patients have a history of exposure to photosensitive substances and poor-quality cosmetic contact history. It should be noted that, once found on the back of the pigmentation, it is recommended to go to a regular hospital, a clear diagnosis, follow the doctor’s instructions standardized treatment.