Multiple osteochondrodysplasia is characterized by a triad of clinical manifestations: abnormal growth of multiple osteochondral fibers, skin pigmentation with milk coffee and precocious puberty. It is also known as McCune-Albright syndrome (MAS) because it was first proposed by Drs. McCune and Albright. The disease is more common in girls and less common in boys. Most of them are accompanied by abnormalities in the function of various endocrine glands. 1. Etiology In recent years, the pathogenesis of this disease has been studied more clearly, and it is believed that this disease is a typical pseudo-precocious puberty. G protein is a heterotrimer composed of three different subunits, namely alpha subunit, beta subunit and gamma subunit. The α subunit binds guanosine diphosphate (GDP) and guanosine triphosphate (GTP). When the ligand with stimulatory function to the target cell arrives, it forms a ligand-receptor complex with the corresponding receptor on the cell surface, which acts on the G protein (Gs protein), so that the affinity of its α subunit for GDP decreases and the affinity for GTP increases, so GTP displaces GDP on the α subunit of Gs protein, forming a ligand-receptor-Gs protein-GTP complex, which can lead to the α subunit dissociation from the β and γ subunits and activation, stimulating adenylate cyclase activation, which increases cAMP synthesis and causes functional activation of target cells. McCune-Albright syndrome is caused by a point mutation in the gene encoding the α-subunit of Gs protein in the cell membrane in early embryonic somatic cells, resulting in the replacement of the arginine at position 201 with histidine or cysteine. This significantly reduces the GTPase activity intrinsic to the Gs protein alpha subunit and causes sustained activation of adenylate cyclase, leading to an increase and accumulation of cAMP levels, which induces proliferation and autonomic hyperfunction of hormone-responsive cells. Therefore, a variety of endocrine gland abnormalities can occur, and precocious puberty is caused by the ovarian luteinized follicular cysts that autonomously produce excessive estrogen. Because of the mutation of somatic cells in the early embryonic stage, chimerism is formed, so the lesions such as bones and skin lesions are segmentally distributed. The clinical manifestations of McCune-Albright syndrome are mainly the following triad of symptoms: ① Endocrine abnormalities, the most prominent symptom is precocious puberty. The most prominent symptom is precocious puberty. Autonomic hyperfunction caused by one or more endocrine gland hyperplasia or adenoma. Most commonly, the ovaries develop autonomic functional follicular cysts, resulting in sex hormone activity and leading to non-GnRH-dependent precocious puberty. Other endocrine gland lesions can also cause hyperthyroidism, cortisolism, and hyperprolactinemia. (2) Abnormal proliferation of multiple bone fibers. It can involve single or multiple bones, mostly in the craniofacial and long bones, with a lateral asymmetric distribution, facial asymmetry, claudication or pain, and skeletal deformity. Scoliosis is more common. (iii) Irregularly bordered cutaneous café-au-lait pigmentation. Most often occur ipsilateral to the bone lesion and rarely beyond the midline. The common locations are the folds at the top of the neck and buttocks. The café-au-lait spots should be differentiated from the skin pigmentation of neurofibromatosis. 3. Diagnosis and differential diagnosis The current diagnostic criteria followed for MAS are: the presence of multiple osteofibrous dysplasia, plus at least one typical endocrine hyperfunction (more common in girls with precocious puberty), and/or specific cutaneous hyperpigmentation. Genetic diagnosis can be determined by genetic analysis of foci such as intracapsular fluid obtained from ultrasound-guided puncture of ovarian follicles and abnormal bone tissue, which reveals mutations in the Gs a gene. It should be distinguished from precocious puberty, osteofibrous dysplasia, non-ossifying fibroma, primary central precocious puberty, and ovarian tumors. Treatment and prognosis The treatment of McCune-Albright syndrome is mainly symptomatic, and there is no effective cure. Precocious puberty has no significant effect on menstruation and fertility in adulthood, but it may lead to early epiphyseal closure and affect height. All endocrine disorders must be treated. Studies have found that the antineoplastic drug tamoxifen is effective in treatment. The drug competes with estradiol to bind estrogen receptors, thus decreasing estrogen levels. In the vast majority of cases of craniofacial osteochondrodysplasia, surgery is not required, with the exception of progressive visual disturbances, severe pain and disfigurement. Diphosphonates are effective in reducing the pain associated with craniofacial osteochondrodysplasia. For bone disease scraping, management of fractures and prevention of deformities can be used. Specific complications caused by bone disease such as narrowing of the optic nerve foramen due to skull base or orbital bone fibrosis leading to visual impairment and even blindness can be tried for surgical correction. It is important to train for strength gain and maintain strength. Swimming and bicycling are the best exercises for patients with osteochondrodysplasia to increase muscle strength to reduce the risk of fracture.