Historically, the human body has often shown a variety of asymmetric changes that are not associated with local and generalized lesions. These asymmetric dysmorphic changes often show a slow progression and are not directly related to time and environmental changes. Historically, there have been many names for them: deviated hypertrophy, congenital deviated hypertrophy, hemiplegia, and partial gigantism, which were first described by Meckel in 1822 and first reported by Wagner in 1839. In the literature, there is a tendency to use the term hemihypertrophy rather than hemihyperplasia to describe these disorders. In fact, hemihypertrophy is more characteristic of this disorder and refers to the deformation of tissues or organs caused by an increase in the number of cells in the tissue or organ. Lateral hypertrophy is an increase in volume without an increase in cell number. Lateral hypertrophy can be all of one half of the torso or a limited part of one side of the body. It can include all organs on the affected side, or one organ, and when accumulated in the muscular system it is also named myohyperplasia. Rowe (1962) classified hemiplegia into three categories: complex hemiplegia, which includes the entire half of the torso; simple hemiplegia, which accumulates one or both limbs; and hemifacial hypertrophy. Hemilateral facial hypertrophy is further divided into true hemifacial hypertrophy (THFH) and partial hemifacial hypertrophy (PHFH).THFH is defined as: an enlargement of the hemifacial skull with the upper border of the frontal bone, the lower border of the lower mandible, the inner border of the midline, and the outer border of the ear including the auricle. THFH is currently reported in more than 50 cases in the literature. PHFH is defined as a hyperplastic change limited to one or several structures of the face. The literature reports 9 cases of true PHFH according to the incomplete statistics published by Lee et al. in 2001 [6]. This data may not be very accurate because there is a great variation in the recognition of this type of malformation, the naming and the language of published articles. Etiology There are many hypotheses and theories so far that try to explain the pathogenesis and causes of the disease, but no single theory can fully explain all hemifacial hypertrophy. For example: hormonal level disorders, neurological disorders, abnormalities of the vascular system, arteriovenous malformations, lymphedema, lymphoid tumors, abnormalities of the intrauterine environment, genetic variants, etc. In vitro culture of osteoblasts on the hypertrophic and normal sides by Yoshimoto et al. showed significantly more hyperplasia of osteoblasts on the hypertrophic side than on the normal side, and they hypothesized that the hyperplasia was caused by a selective alteration of the fibroblast growth factor and receptor signaling chain on the affected side. Bencze et al. reported a case of left-sided HFH with strabismus in three generations of the same family, suggesting that the condition is genetic in nature. Clinical presentation and diagnosis Hemifacial hypertrophy is a rare developmental asymmetry characterized by hyperplastic hypertrophy of one half of the face or part of the face, which may be accompanied by pituitary disorders causing acromegaly or hypertrophy of other parts of the body. This type of deformity usually stops automatically with age, especially in adolescence, and is more common in males. The main feature is the progressive hyperplasia and enlargement of unilateral facial bone and soft tissues, causing facial asymmetry. The affected maxilla and mandible, zygoma, skull, hemifacial lip and ear are enlarged. Patients with hemifacial hypertrophy have more soft tissue changes, such as: scalp thickening, skin thickening, increased sebaceous and sweat gland function, capillary dilation and multiple nevi, tongue asymmetry due to tongue hypertrophy, and prominent bacteriophageal papillae hyperplasia. There is hyperplastic hypertrophy of the buccal mucosa, megalodontia or microdontia, malocclusion, premature tooth eruption, crown or root hyperplasia of cuspids, bicuspids and first molars, and in severe cases, oral soft and hard tissue changes such as temporomandibular joint ankylosis. Patients with hemifacial hypertrophy may also have a wide range of hard tissue hyperplasia, such as polydactyly, syndactyly, missing finger deformity, scoliosis, pelvic tilt, and deformed feet. Involvement of the central nervous system may be associated with spondylolisthesis, epilepsy, and strabismus in 15-20% of patients with mental retardation. There is a relatively rare special type of hemifacial hypertrophy that involves only the facial muscles but not other parts and organs, and this type of patient is named hemifacial myohyperplasia. 3.2 Diagnosis and differential diagnosis: 1, congenital disease that can be found at birth, progressive hypertrophy with development, and stop growing around puberty. 2, clinical examination compound appeal clinical manifestations, no other similar syndrome manifestations. Histological examination can see the increase of normal tissue cells without the appearance of abnormal structures and cells. 3.Impact examination has a characteristic limited affected facial bones or local hyperplasia hypertrophy. The differential diagnosis of the disease is particularly important because there are many diseases or syndromes that are accompanied by hemifacial asymmetry, such as progressive hemifacial atrophy (Romberg’s disease), osteochondrodysplasia, neurofibroma, hemangioma, lymphadenoma, Klippel-Trenaunay syndrome, segmental odontomandibular dysplasia, and so on. It is necessary to combine the patient’s medical history, clinical manifestation and imaging examination to determine the diagnosis. 4.Treatment options: caries and periodontal treatment; facial osteoplasty (including zygomatic bone; maxilla, frontal bone, mandible); chinplasty, orthognathic surgery; liposuction, buccal fat pad removal; face lift; arthroplasty; partial excision of bite muscle or superficial parotidectomy, etc. Since the majority of HFH patients are treated for cosmetic reasons, this type of surgery is often determined after the patient’s development is complete. Skeletal surgery includes osteotomy and orthognathic surgery. In China, Li Zili summarized 33 patients with hemimandibular hypertrophy treated by orthognathic orthognathic surgery at the North Medical and Dental Hospital, who used modern orthognathic methods, including: maxillary LeFort type I osteotomy, maxillary LeFort type I block osteotomy, maxillary posterior osteotomy, affected condyle resection and joint reconstruction, sagittal splitting osteotomy or vertical osteotomy The results were very satisfactory. The results are very satisfactory. The prognosis of HFH is very good, there are no reports of malignant changes or death due to this, and bone regeneration after bone surgery is rare. Psychological counseling should be provided before treatment to lower the patient’s expectations. Since this type of surgery requires a step-by-step approach and many planned operations to achieve the final result, it is necessary to gain the patient’s trust to cooperate in its implementation. HFH is a very rare disease, and for non-craniomaxillofacial dentists, the diagnosis and treatment is even more difficult, especially for its subclassification, true and partial HFH understanding requires specialized knowledge. Only a clear diagnosis can achieve a targeted treatment.