Unilateral atrophy is a progressive atrophy of one limb or trunk tissue, which is characterized by thinning of one skin, reduction of subcutaneous fat and reduction of bones. Atrophy confined to one side of the head and face is called facial atrophy. The cause of unilateral atrophy is not clear. Pathologically, connective tissue, especially subcutaneous adipose tissue, is involved first, and then skin, sebaceous glands and hair are gradually involved. In severe cases, bones, kidneys and cerebral hemispheres are involved.