The common causes of dark brown patches on legs are nevus, seborrheic keratosis and stasis dermatitis.
1. Nevus pigmentosus: when melanocytes proliferate benignly and gather together, it can lead to dark brown patches on legs, i.e. nevus pigmentosus.
2. Seborrheic keratosis: aging of the skin and long-term exposure to ultraviolet rays can lead to the appearance of light brown to black round or ovoid papules and plaques on the skin, i.e. age spots.
3. Siltation dermatitis: if microvascular lesions on the legs, causing increased permeability of local capillaries and elevated venous pressure, which will cause chronic inflammation of the capillaries on the legs due to stagnation and blockage of blood, under the stimulation of inflammatory factors, the affected skin may develop dark brown pigmentation and macular rash.
The appearance of dark brown patches on the legs may also be related to other factors, it is necessary to go to the regular hospital to identify the cause of the disease in a timely manner, and under the guidance of specialists to choose the appropriate method of standardized treatment.