NOTCH2 and hereditary disease: Hajdu–Cheney syndrome (HCS) is a rare genetic disorder caused by a mutation in the NOTCH2 gene characterized by short stature, severe osteoporosis, acro-osteolysis, dysmorphic facial features (mild hypertelorism with telecanthus, low-set ears, long philtrum, short neck), and dental abnormalities (highly arched palate, impaired tooth eruption, premature tooth loss).