White patches on the calf may be caused by anemic nevus, vitiligo, post-inflammatory hypopigmented spots and other diseases. 1. anemic nevus: anemic nevus is a localized skin hypopigmentation caused by abnormal development of vascular tissues, manifesting itself as a pale skin discoloration, prevalent in the trunk, some patients will appear in the lower legs. 2. Vitiligo: Vitiligo is a disease in which the destruction of melanocytes causes white patches on the skin. The cause of the disease is not yet clear, and it may be related to autoimmune disorders, genetic factors, neurochemicals, and so on. The patient’s skin will appear white spots, can also appear in a part alone, such as calves and other places. 3. Post-inflammatory hypopigmentation spots: white patches on the calves may also be post-inflammatory hypopigmentation spots, which are caused by local skin inflammation, destruction of melanin in the melanocytes of the basal layer, resulting in localized skin hypopigmentation. There are more reasons for white patches on the calf, so it is recommended to consult a doctor for a clear diagnosis.