The appearance of brown patches on the back may be caused by localized hyperpigmentation, coffee spots, seborrheic keratosis and so on.
1. Localized hyperpigmentation: some skin diseases, such as folliculitis, lichen planus, etc., will lead to local precipitation of melanin particles, forming localized hyperpigmentation, resulting in brown patches on the back.
2. Coffee spot: hereditary skin disease, due to hyperactivity of keratinocytes and melanocytes, producing a large amount of melanin. This leads to the appearance of brown patches on the back.
3. Seborrheic keratosis: a benign epidermal tumor caused by keratinocyte hyperplasia, which manifests itself as a kind of mild elevation on the surface of the skin, brown or dark brown papules, plaques, covered with greasy scales. It can also cause brown patches on the back.
If you have brown patches on your back, there may be other conditions, so you can go to the hospital and have the relevant examinations done to clarify the situation and take appropriate measures.