Hajdu–Cheney syndrome

Hajdu–Cheney syndrome, also called acroosteolysis with osteoporosis and changes in skull and mandible, arthrodentoosteodysplasia, and Cheney syndrome, is an extremely rare autosomal dominant congenital disorder of the connective tissue characterized by severe and excessive bone resorption leading to osteoporosis and a wide range of other possible symptoms. Mutations in the NOTCH2 gene, identified in 2011, cause HCS. HCS is so rare that only about 70 cases have been reported worldwide, since the discovery of the syndrome in 1948.