NOTCH2 and acroosteolysis dominant type: Hajdu-Cheney syndrome (synonyms: HCS, acroosteolysis dominant type, Orpha number: 955, acroosteolysis with osteoporosis and changes in skull and mandible, arthro-dento-osteodysplasia, arthrodentoosteodysplasia, Cheney syndrome, cranioskeletal dysplasia with acroosteolysis, familial osteodysplasia, hereditary osteodysplasia with acro-osteolysis, HJCYS, and serpentine fibula-polycystic kidney syndrome/SFPKS) is a very rare autosomal-dominant disease with mutations in the NOTCH2 gene.