[Abstract] Progressive hemifacial atrophy is a group of syndromes characterized by chronic, progressive atrophy of some or all tissues of the craniofacial region unilaterally, sometimes involving other parts of the ipsilateral body. [Alias] Progressive hemifacial atrophy; progressive laminar dysplasia syndrome; Romberg’s disease; Parry-Romberg syndrome. [Etiology] Unknown. The more convincing theory is the sympathetic theory, but there are also trigeminal theory, scleroderma theory, central nervous system theory, infection, and injury. It may also be autosomal dominant, but the ectopic rate is very low. [The sympathetic nerve theory suggests that it is related to abnormal sympathetic nerve function. Animal experiments have shown that stimulation of the sympathetic nerve in dogs for several days resulted in a decrease in subcutaneous adipose tissue and changes similar to parafacial atrophy, whereas stimulation of the parasympathetic nerve had the opposite effect. In rats, cutting the sympathetic nerve on one side of the face also produced parafacial atrophy-like changes on the opposite side. The detailed mechanism remains to be elucidated. [Pathology] Atrophy of the skin, subcutaneous fat, connective tissue, sebaceous glands, muscles, cartilage and bone is the most obvious. Muscle atrophy is the atrophy of the connective tissue, and the muscle fibers themselves are not atrophied. [The onset of the disease is insidious and the development is slow, and the disease generally stabilizes in about 3 years. Craniofacial abnormalities: usually starts from the corners of the mouth, infraorbital, nasal root or cheek, and gradually expands to a comprehensive atrophy of skin, subcutaneous tissue, muscle and bone on one side of the craniofacial area, with hair loss, possibly accompanied by local abnormal sensation or pain, and eventually forming an asymmetrical face that is significantly smaller on the affected side than on the healthy side. In some patients, longitudinal skin wrinkles appear from the middle of the forehead to the nose down to the middle of the chin, forming knife-like marks, or “saber-cut” type changes. About 5% to 10% of patients have bilateral involvement. Abnormalities of the oral and maxillary system: atrophy of the affected maxilla and mandible, shortening of the mandibular body and ascending branch; atrophy of the alveolar bone, local open jaw; lip atrophy, exposure of teeth on the affected side; tongue atrophy, extension of the tongue to the affected side; atrophy of the salivary glands on the affected side, reduced secretion, and dry mouth. Ophthalmology: orbital fat atrophy, sunken eyeball; suborbital bone atrophy, suborbital shift; ocular muscle paralysis, rabbit eye, ptosis and the presence of keratitis, iritis, chorioretinitis and other manifestations of ocular infections. Central nervous system abnormalities: epilepsy or epileptiform seizures, with trigeminal neuralgia and facial palsy early in the course of the disease, and migraine in the later stages. Other abnormalities: about 7% of patients have ipsilateral trunk, visceral, and upper and lower limb atrophy changes. [Diagnosis] The diagnosis is not difficult based on the history and clinical manifestations, and treatment is taken if necessary. Pay attention to differentiate it from the hemifacial microsomia caused by the developmental disorders of the first and second gill arches, which is a small hemifacial face caused by the hypoplasia of soft and bony tissues, rather than the atrophy of tissues, and the hypoplasia of the maxilla and mandible and zygomatic and masticatory muscles, small ear and inner ear deformities, small mouth, mislift and other deformities. [Treatment] There is no curative treatment, only symptomatic supportive treatment. Acupuncture, physiotherapy, muscle function training, and Chinese medicine can be used to activate blood circulation and remove blood stasis. After the condition is stabilized, plastic surgery is possible. [Prognosis] Most of the cases can be terminated at any stage of the lesion on their own.